Molecular Metal Phosphonates - American Chemical Society

Review pubs.acs.org/CR

Molecular Metal Phosphonates Joydeb Goura† and Vadapalli Chandrasekhar*,†,‡ †

Department of Chemistry, Indian Institute of Technology-Kanpur, Kanpur 208 016, India National Institute of Science Education and Research, Institute of Physics Campus, Sachivalaya Marg, Sainik School, Bhubaneswar, Orissa 751 005, India

‡

9.1. Chromium 9.2. Molybdenum 9.3. Tungsten 10. Group 7 Phosphonates 10.1. Manganese 10.1.1. MnII 10.1.2. MnIII 10.1.3. MnIV 10.1.4. MnII/MnIII 10.1.5. MnIII/MnIV 10.2. Technicium and Rhenium 11. Group 8 Phosphonates 11.1. Iron 11.2. Ruthenium and Osmium 12. Group 9 Phosphonates 12.1. Cobalt 12.2. Rhodium and Iridium 13. Group 10 Phosphonates 13.1. Nickel 13.2. Palladium 13.3. Platinum 14. Group 11 Phosphonates 14.1. Copper 14.2. Silver and Gold 15. Group 12 Phosphonates 15.1. Zinc 15.2. Cadmium 15.3. Mercury 16. Lanthanide Phosphonates 17. Molecular Actinide Phosphonates 19. Coordination Features of the Phosphonate Ligand 19. Applications of Molecular Metal Phosphonates 19.1. Magnetic Properties 19.2. Other Properties 20. Conclusion Author Information Corresponding Author Notes Biographies Acknowledgments Abbreviations Dedication References

CONTENTS 1. Introduction 2. Phosphonic Acids 2.1. Synthesis of Phosphonic Acids 2.1.1. Arbuzov Reaction 2.1.2. Michaelis−Becker Reaction 2.1.3. Metal−Halogen Exchange 2.1.4. Nucleophilic Addition to Carbonyl Groups 2.1.5. Clay Reaction 2.1.6. Metal-Catalyzed Reactions 2.2. Solid-State Structures of Phosphonic Acids 3. Alkali and Alkaline Earth Metal Phosphonates 4. Group 13 Phosphonates 4.1. Boron 4.2. Aluminum 4.3. Gallium 4.4. Indium 5. Group 14 Phosphonates 5.1. Tin 5.2. Lead 6. Group 15 Phosphonates 6.1. Antimony 6.2. Bismuth 6.3. Tellurium 7. Group 4 Phosphonates 7.1. Titanium 7.2. Zirconium and Hafnium 8. Group 5 Phosphonates 8.1. Vanadium 8.1.1. VIII 8.1.2. VIV and VV 8.1.3. VIV 8.1.4. VV 8.1.5. VIV/VV 8.2. Niobium 8.3. Tantalum 9. Group 6 Phosphonates © XXXX American Chemical Society

A E E E F F H H H I I J J J K L M M P P P Q R S S U U U V W W W Y AE AF AF

AF AH AK AK AK AK AN AQ AR AU AU AV AV BG BH BH BQ BQ BQ BU BV BW BW CA CB CB CF CG CH CL CN CS CT CV CV CV CV CV CV CW CW CX CX

Received: February 20, 2015

A

DOI: 10.1021/acs.chemrev.5b00107 Chem. Rev. XXXX, XXX, XXX−XXX

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1. INTRODUCTION The carboxylate ligand, [RCO2]−, is one of the most versatile and hence also one of the most ubiquitous ligands in coordination chemistry.1−4 Although fairly simple coordination modes are exhibited by the carboxylate (and multicarboxylate) family of ligands (Figure 1), their utility has been immense as

Table 1. pKa Values of Representative Carboxylic and Phosphonic Acids

Figure 1. Coordination modes of the carboxylate ligands.1−4 The coordination notation is adapted from refs 1−4.

compounds

pKa1

HCOOH CH3CO2H F3CCO2H (COOH)2 PhCO2H CH3PO3H2 EtPO3H2 t-BuPO3H2 F3CPO3H2 Cl3CPO3H2 PhPO3H2 PhCH2PO3H2 HO2CCHCHCO2H phthalic acid H3PO4

3.77 4.76 3.07 1.23 4.17 2.33 2.39 2.79 1.16 1.63 3.15 3.30 1.92 2.98 1.97

pKa2

ref

7.76 7.98 8.88 3.93 4.81 8.26 8.40 6.23 5.28 6.82 (pKa3 = 12.5)

7 8 8 7 7 11 11 11 11 11 11 11 9 7 10

4.19

ligand shows both similarities and dissimilarities regarding the carboxylate ligand. These are summarized in Figure 4. Because of its versatile coordination behavior and the capability to bind multiple metal ions, interaction of the phosphonate ligands with metal ions often results in the formation of metal phosphonates possessing extended structures (one-, two-, and three-dimensional).14 Such coordination polymers have been very well studied for a long period of time due to their structural interest and also due to their potential applications in various fields including ion exchange,15 catalysis,16 adsorption and separation,16 proton conductivity,17 water treatment,15 biotechnology,15,16 photochemistry,18 dental medicine,16 cancer treatment,16 magnetism,16,19 magnetic refrigeration,1,20−25 etc. Representative examples of metal phosphonates possessing extended structures are shown in Figures 5−7.26−28 A few other examples are discussed below. Clearfield et al. synthesized a zigzag 1D MnII coordination polymer involving the reaction of MnII salts and N(CH2PO3H)3. Although the ligand possesses multiple phosphonate coordinating units, the resultant product is a one-dimensional coordination polymer due to the fact that the central nitrogen is protonated. Further, only two of the monoanionic phosphonate groups are involved in coordination; the third unit is involved in interchain hydrogen-bonding interactions involving P−OH and N−H units along with the additional participation of coordinated water molecules (Figure 8).29 Zubieta et al. prepared a two-dimensional CuII phosphonate polymer, using 2,6-carboxynaphthalene phosphonic acid, HO3PC10H6CO2H (H3cnp).30 The carboxylic acid group is only involved in hydrogen-bonding interaction; the 2D-polymer is formed through the coordination action of the phosphonate unit (Figure 9).30

exemplified from their crucial role in assembling zerodimensional compounds to three-dimensional coordination polymers, from biomimetic model systems to metal−organic frameworks (MOFs).5,6 Attempts to mimic and extend the versatility of the carboxylate ligand system have found expression in exploring other families, one of which, the phosphonate family, [RPO3]2−, is the subject matter of this Review. Phosphonate, [RPO3]2−, and the related ligand [{RP(O)2(OH)}]− are derived from the corresponding phosphonic acids RP(O)(OH)2, which are distinguished by the presence of a P−C bond. The phosphorus atom in these systems is present in an oxidation state of +5, is tetra-coordinate, and supports a coordination platform of oxygen atoms that can bind to multiple metal ions. This aspect will be commented upon subsequently. The phosphonic acids, themselves, belong to a general class of phosphorus-based acids as shown in Figure 2. The pKa1 values of organophosphonic acids are lower than those of the corresponding carboxylic acids RC(O)OH or the phosphoric acids (Table 1).7−11 As in the case of the carboxylic acids, however, the pKa values can be modulated in the phosphonic acids by varying the substituent on the phosphorus atom (Table 1). Monoanionic, [RPO2(OH)]−, or dianionic, [RPO3]2−, phosphonates, can be obtained by the deprotonation of [RP(O)(OH)2] using different bases.12 These are excellent multidentate ligands. Thus, [RPO3]2−, due to the presence of three potential coordinating oxygen atoms, can bind to a maximum of nine metal centers (Figure 3). Because of the presence of the additional coordinating oxygen atom, the coordination behavior of the phosphonate

Figure 2. Schematic representation of phosphorus-based acids. B


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Figure 3. Possible coordination modes of the phosphonate ligands. The coordination notation shown in this figure is according to Harris et al.13

Figure 4. (a) Similarity in the coordination modes between phosphonate and carboxylate ligands. (b) Differences in coordination modes between phosphonate and carboxylate ligands. C


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(H8L), a tetrahedral phosphonate ligand.31 The ligand H8L upon metalation with CuII salts forms a doubly interpenetrated diamondoid solid [{Cu3(H3L)(OH)(H2O)3}·H2O·MeOH]n (Figure 10).31 The area of metal phosphonates possessing extended structures has been reviewed several times,14−19 most recently, in the form a comprehensive monograph.32−34 In contrast to these systems, the corresponding molecular metal phosphonates (zero-dimensional compounds) have only became prevalent in the last two decades. This is mainly because of the difficulty in curtailing the coordination propensity of the phosphonate ligand. This goal has been achieved by three important synthetic strategies. (1) The first is using ancillary ligands that can block the coordination sites on the metal ion, because of which the phosphonate ligand has limited opportunities to proliferate the metal assembly. This concept will be exemplified in the various compounds that will be discussed herein. At this stage, two examples will suffice to illustrate this point. The reactions of CuII salts and tert-butylphosphonic acid in the presence of 3,5-di-tert-butyl pyrazole afford a discrete, tetrameric CuII phosphonate in a distorted cube-shaped structure [Cu2(3,5-tBu2PzH)2(t-BuPO3)2]2 (Figure 11).35 The bulky 3,5-di-tertbutyl pyrazole ligand not only occupies the coordination sites around CuII, but also, because of its steric bulk, prevents agglomeration of the ensemble and limits the nuclearity to four. Similarly, in a reaction involving MnII salts and tertbutylphosphonic acid in the presence of 2,6-bis(pyrazol-3yl)pyridine (dpzpy) (and using triethylamine as the base), a molecular trinuclear triangular MnII phosphonate complex [Mn3(t-BuPO3)2(dpzpy)3] was isolated (Figure 12).36 In this instance also, the ancillary ligand blocks some of the coordination sites on the metal ion and therefore limits the number of coordination sites that are available around a metal ion. This results in the isolation of discrete zero-dimensional compounds. (2) The use of sterically hindered phosphonic acids can also lead to the formation of discrete molecular phosphonate complexes. Steric hindrance around ligands has been used very effectively in main-group chemistry for kinetically stabilizing reactive and unstable compounds that include main-group element compounds containing multiple bonds or low-valent compounds.37−43 Although the principle is different, in phosphonate chemistry, steric hindrance has been used to limit the nuclearity of the molecular phosphonates. Examples of this are shown in Figures 13 and 14. Thus, a dinuclear cerium complex, [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4], was isolated in the reaction between a CeIII salt and Ph3CPO3H2 (Figure 13).44 Similarly, a tetranuclear [Co4(Ph3CPO3)4Py4] complex was obtained in the reaction involving a CoII salt and Ph3CPO3H2. Pyridine, which was used as a base, also functions as a monodentate ligand and occupies one of the coordination sites.45 (3) The third is cluster expansion. In this methodology, a preformed metal complex containing certain labile ligands is used as a precursor to react with a phosphonate ligand. The replaceable ligand has less coordinating sites than the phosphonate. Consequently, although the core of the metal complex precursor is retained, the cluster is expanded with the aid of the phosphonate ligand. This principle is exemplified in Schemes 1 and 2.46,47 With this background, this Review will attempt to summarize the progress in the area of molecular phosphonates. After a brief discussion on the synthetic and structural aspects of

Figure 5. A pillared structure of [Zn3(4-O2CC6H4PO3)2]n.26 Adapted from ref 26. Copyright 2010 The Royal Society of Chemistry.

Figure 6. 2D-coordination polymer, [{Co(2-pyHCH2PO3H)(H2O)}ClO4]n (2-PyCH2PO3H2 = 2-pyridylmethylphosphonic acid).27 Adapted from ref 27. Copyright 2011 The Royal Society of Chemistry.

Figure 7. 3D-supramolecular structure of [Zn3(HL)2]n [H4L = N-methyliminobis(methylene-phosphonic acid), [CH3N(CH2PO3H2)2].28 Adapted from ref 28. Copyright 2002 American Chemical Society.

Shimizu and co-workers reported a copper(II) phosphonate containing 1,3,5,7-tetrakis(4-phosphonophenyl) adamantane D


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Figure 8. 1D-coordination chain of [Mn{HN(CH2PO3H)3(H2O)3}]n.29 Adapted from ref 29. Copyright 2002 American Chemical Society.

Figure 11. A distorted cubic tetranuclear CuII phosphonate, [Cu2(3,5t-Bu2PzH)2(t-BuPO3)2]2.35 Figure 9. 2D-coordination polymer, [Cu(O3PC10H6CO2H)]n.30 Adapted from ref 30. Copyright 2010 Elsevier Masson SAS.

Figure 12. A trinuclear MnII phosphonate, [Mn3(t-BuPO3)2(dpzpy)3].36

for various types of diseases such as diabetes, asthma, inflammation, heart failure, cancer, malaria, and HIV.48 A recent review indicates these medicinal aspects of phosphonic acids.48 In view of this importance as well as their use in coordination chemistry, several synthetic strategies are now available for the preparation of phosphonic acids. Because this aspect has been dealt with in considerable detail in a recent review,48 only a summary of the synthetic procedures will be discussed herein. Literature survey shows that there are several types of organophosphonic acids with various types of substituents. Some recent representative examples of these are shown in Figure 15.

Figure 10. 3D-coordination polymer, [{Cu3(H3L)(OH)(H2O)3}· H2O·MeOH]n.31 Adapted from ref 31. Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

phosphonic acids, metal phosphonates will be covered systematically, first involving main-group elements of groups 13−15, followed by those of transition metals and rare earth elements. The applications of molecular phosphonates, particularly in the area of molecular magnetism, will be covered in brief toward the end.

2.1. Synthesis of Phosphonic Acids

The synthesis of phosphonic acids can be accomplished by any of the following methods. 2.1.1. Arbuzov Reaction. This is one of the oldest synthetic methods that involves the reaction of electrophilic alkyl halides with nucleophilic trialkylphosphites (Scheme 3). The product of the reaction is a dialkylphosphonate, which has

2. PHOSPHONIC ACIDS In addition to their utility in coordination chemistry, phosphonic acids are also quite important as potential drugs E


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Scheme 2. A Tetranuclear CuII Complex, [Cu4(L)2(tBuPO3)] (H3L = 1,3-Bis(salicylideneamino) propan-2-ol), Prepared by the Cluster Expansion Strategy47

applicable to the preparation of alkyl phosphonic acids, and an important feature of this reaction is that it requires high temperature (provided by carrying out the reaction in high boiling solvents under reflux conditions), although the reaction can be carried out in the absence of a base. The mechanism of this reaction has been probed, and both SN2 and SN1 pathways have been found to be operative.48 Schemes 4−6 summarize some recent examples of benzyl phosphonic acids that were prepared by the application of the Arbuzov reaction.49−54 Notice that both benzyl chlorides and bromides could be utilized.49−54 Also, it may be noticed that the reaction is tolerant to the variation of substitution on the benzene ring. 2.1.2. Michaelis−Becker Reaction. The Michaelis− Becker reaction is a variation of the Arbuzov reaction, but involves the use of a dilakyl phosphonate, HP(O)(OR′)2, as the substrate. Although this reaction is also noncatalytic, the main advantage appears to be that the reaction can be accomplished at lower temperatures than the Arbuzov reaction. However, the use of a strong base is needed to deprotonate the P−H bond (Scheme 7). Thus, the reaction is not suitable for base-sensitive substrates. This reaction mainly proceeds via an SN2 pathway. Similar to the Arbuzov reaction, the Michaelis−Becker reaction can be used for the preparation of dialkyl phosphonates, which can be hydrolyzed to alkyl phosphonic acids; the largest variety of phosphonic acids prepared by this method involves benzyl phosphonic acids.48 2.1.3. Metal−Halogen Exchange. Organolithium or Grignard reagents are used to react with a dialkyl chlorophosphonate such as ClP(O)(OEt)2 to afford RP(O)(OEt)2

Figure 13. A dinuclear cerium complex, [Ce 2 {Ph 3 CPO 2 (OEt)}4(NO3)2(H2O)4].44 Adapted from ref 44. Copyright 2008 The Royal Society of Chemistry.

Figure 14. A tetranuclear CoII phosphonate, [Co4(Ph3CPO3)4Py4], possessing a D4R cubic core.45 Adapted from ref 45. Copyright 2007 The Royal Society of Chemistry.

to be subsequently hydrolyzed to afford the corresponding phosphonic acid (Scheme 3). In general, this reaction is

Scheme 1. Preparation of a Hexanuclear Manganese Cage, [Mn6O2(PhPO3)2{Ph(H)PO2}2 (O2CPh)8(py)2], from a Trinuclear Precursora

a

The phosphonate ligand, [PhPO3]2−, is formed in situ.46 F


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Figure 15. Representative examples of various types of phosphonic acids.

Scheme 3. General Synthetic Scheme for the Arbuzov Reaction48

Scheme 4. Synthesis of 2,3,5,6-Tetramethyl Benzylphosphonic Acid49

via a metal−halogen exchange pathway. RP(O)(OEt)2 can be hydrolyzed to afford the corresponding phosphonic acid. This reaction can be utilized to prepare alkyl-, alkynyl-, and arylsubstituted phosphonates (Scheme 8).48 G


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Scheme 5. Synthesis of p-Nitrobenzylphosphonic Acid50

Scheme 9. General Synthetic Scheme for Nucleophilic Addition to Carbonyl Groups for the Preparation of Phosphonic Acids48

Scheme 6. Synthesis of 5-Phosphonomethyl-8hydroxyquinoline51

Scheme 7. General Synthetic Scheme for the Michaelis− Becker Reaction48

Scheme 10. Synthesis of 1-Amino-1-cyclohexylphosphonic Acid22

Scheme 11. Preparation of Cyclopentylphosphonic Acid by the Clay Reaction52−54 Scheme 8. Synthesis of Alkyl/Aryl or Alkyne-Substituted Phosphonic Acids Utilizing Reactions with the Grignard Reagent48 Scheme 12. General Synthetic Scheme for Metal-Catalyzed Phosphonic Acid Synthesis48

2.1.4. Nucleophilic Addition to Carbonyl Groups. This reaction involves a nucleophilic addition of HP(O)(OR′)2 to various types of aldehydes and ketones. The reaction affords phosphonates where the α-carbon can have a substituent such as an −OH or a −NH2. Subsequent hydrolysis of these compounds affords the corresponding phosphonic acids, which contain an additional functional group. This reaction needs a strong base in the form of a lanthanide amide [{(TMS)2N}3Ln(μ-Cl)Li(THF)3] (TMS = tetramethysilane) or a Lewis base such as potasium alkoxide/crown ether complex or MoO2Cl2 as a catalyst. This procedure is applicable for alkyl/aryl aldehydes or ketones and α,β unsaturated/aliphatic aldehydes (Scheme 9).48 A recent example involving the synthesis of an aminefunctionalized phosphonic acid by the above route is shown in Scheme 10.22 2.1.5. Clay Reaction. This reaction involves an alkyl halide and PCl3 in the presence of AlCl3. In situ hydrolysis of the reaction mixture affords the corresponding phosphonic acid. This reaction is applicable to the preparation of alkyl

phosphonic acids. Scheme 11 illustrates the utility of this reaction for the preparation of cyclopentyl phosphonic acid.52−54 2.1.6. Metal-Catalyzed Reactions. All of the reactions described above for the preparation of RP(O)(OR′)2 are stoichiometric and are noncatalytic. Many metal-catalyzed reactions are now well-known for the preparation of RP(O)(OR′)2 involving sp3, sp2, and sp carbon atoms (Scheme 12). The phosphonating agents are either dialkyl phosphonate or trialkyl phosphite.48 H


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Figure 16. Solid-state structural forms of phosphonic acids.55−62 (See Table 2.)

Figure 17. 1D-supramolecular structure of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3).60 Adapted from ref 60. Copyright 2013 The Royal Society of Chemistry.

2.2. Solid-State Structures of Phosphonic Acids

ular structures, known so far, contain only O−H---O interactions.60 Table 2 summarizes the solid-state structural forms found among phosphonic acids.55−62

In comparison to carboxylic acids, structural investigations on phosphonic acids are limited. To date, only four types of structural forms [dimer, hexameric cages, 1D-sheets, and 2Dsheets] are known (Figure 16).55−62 In addition to the structural forms shown in Figure 17, recently, the structure of 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3) phosphonic acid revealed that as a result of intermolecular hydrogen bonding through quinoline N−H and phosphonic acid O−H groups, a 1D-supramolecular architecture is formed (Figure 17). All previous supramolec-

3. ALKALI AND ALKALINE EARTH METAL PHOSPHONATES Discrete homometallic phosphonates involving only the alkali or the alkaline earth metal ions are absent, except for one example, [Ca3{O3PCH(OH)CO2}2·14H2O] (Figure 18).63,64 This compound was prepared in the reaction of water-soluble I


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Roesky and co-workers examined the reaction of t-BuP(O)(OH)2 with BEt3 and observed that despite the low reactivity of the B−C bond, ethane elimination occurs at a reasonably moderate temperature of 100 °C affording the molecular compound, [t-BuPO3BEt]4, in very good yields.65 The molecular structure of [t-BuPO3BEt]4 reveals that it possesses a distorted cubic core, which is reminiscent of the D4R SBU of zeolites, with the alternate corners of the cube being occupied by boron and phosphorus atoms while the centers of the edges contain oxygen atoms (Scheme 13).65 Interestingly, this molecule is quite stable even in electron impact mass spectroscopic conditions and reveals a molecular ion peak at m/e 704. The average P−O bond distances in the molecule (∼1.50 Å) have been found to be longer than a PO bond (1.45−1.46 Å) and shorter than a P−O bond (1.59−1.60 Å).65 Kuchen et al. were able to prepare an analogous tetranuclear borophosphonate in the reaction of PhBCl2 with t-BuP(O)(OSiMe3)2. The driving force in this reaction is the facile elimination of Me3SiCl (Scheme 14 and Figure 20).66 Interestingly, all known borophosphonates to date are tetranuclear and are summarized in Table 3.65−69 The search for borophosphonates with a different nuclearity is likely to be an interesting endeavor.

Table 2. Solid-State Structures of Phosphonic Acids phosphonic acid

structural type

Ph3CPO3H2 t-BuPO3H2 Ph3CPO3H2 t-BuPO3H2 2,4,6-i-Pr3C6H2PO3H2 5-phosphonomethyl-8-hydroxyquinoline (5pm8hqH3) 3-pyridylphosphonic acid (3-C5NH5PO3H2), 5-(dihydroxyphosphoryl)nicotinic acid 3,5-pyridinediyldiphosphonic acid 4-OMe-C6H4−PO3H2 PhPO3H2 Ph3CPO3H2 benzene-1,3,5-tri-p-phenylphosphonic acid, [1,3,5{p-C6H4P(O)(OH)2}3C6H3]

ref

dimer hexameric cage -do1D-sheet -do-do-

44, 55 56 44, 55 56 195 60

-do-

61

1D helical 2D-sheet -do-do3Dsupramolecular

61 57 58, 59 44, 55 62

4.2. Aluminum

The known aluminophosphonates are listed in Table 4. As can be seen, the nuclearity of the aluminophosphonates varies from 2 to 16.70−81 Representative examples of these are depicted in Figures 21−24. Tetranuclear derivatives in a cuboidal architecture, resembling the D4R SBUs of zeolites, are among the most common derivatives. These have been obtained in various ways. The most common route involves the reaction of trialkylaluminums or disobutylaluminum hydride with RPO3H2. Elimination of alkane (and hydrogen in the case of i-Bu2AlH) is the driving force for the reaction. A representative molecular structure is shown in Figure 21. The cage consists of two eight-membered rings that are fused with each other such that a cubic architecture is obtained whose alternate corners are occupied by aluminum and phosphorus and whose edges contain oxygen atoms.70 In a similar reaction, involving t-BuPO3H2 and AlMe3, a hexanuclear derivative, [MeAlO3PBu-t]6, possessing a D6R core structure was isolated (Scheme 15).71 It may be noticed that in both of these cases, the aluminum center retains an alkyl substituent. Efforts to link such cages, in a bottom-up approach, to afford larger ensembles have not been successful, although examples involving phosphate ligands are known, [Al 10 {μ3 -O3 P(OR)} 12 (μ 3 -O) 2 (O−Pr-i) 2 (THF) 4 ] and [Al 8 (μ 3 -O 3 P(OR)} 8 (μ2 -HO 3 P(OR)} 2 (μ 3 -O) 2 (μ 2 -OH)2 (THF) 4 ] (R = 2,6-i-Pr2C6H3).72 Efforts to involve coordination through a heterocyclic nitrogen by using 2-pyridyl phosphonic acid also resulted in a tetranuclear derivative (Table 4). These derivatives are however cationic complexes and possess eight counteranions. The eight-membered ring constituents of the dinuclear aluminum phosphonate cages can be liberated in reactions with n-Bu4NHF2 (Scheme 16). In the resultant anionic aluminum phosphonates, the eight-membered ring is puckered and the aluminum atoms are fluorinated and possess two fluorine substituents each.73 The utility of the fluoride ion as a structure directing agent was most dramatically demonstrated in the reaction of Cs(i-Bu3AlF) with t-BuPO3H2, which afforded a complex

Figure 18. A trinuclear linear CaII phosphonate, [Ca3{O3PCH(OH)CO2}2·14H2O].63 Adapted from ref 63. Copyright 2010 American Chemical Society.

Table 3. Molecular Borophosphonates reactants

compounds

nuclearity/ structure

ref

BEt3, t-BuPO3H2 PhBCl2, t-BuP(O)(OSiMe3)2 CH3PO3H2, BEt3 CH3PO3H2, (s-Bu)3B EtPO3H2, BEt3 EtPO3H2, (s-Bu)3B t-BuPO3H2, BEt3 t-BuPO3H2, (s-Bu)3B PhPO3H2, BEt3 PhPO3H2, (s-Bu)3B

[t-BuPO3BEt]4 [PhBO3PBu-t]4 [MePO3BEt]4 [MePO3BBu-s]4 [EtPO3BEt]4 [EtPO3BBu-s]4 [t-BuPO3BEt]4 [t-BuPO3BBu-s]4 [PhPO3BEt]4 [PhPO3BBu-s]4

tetranuclear/cubic -do-do-do-do-do-do-do-do-do-

65 66 68 68 68 68 68 68 68 68

CaII salt and H2O3PCH(OH)CO2H. The structure of the compound reveals that it contains two terminal CaII ions, which are bound by the chelating action of the [COO]− and [−CHOH] part of the ligand. The central CaII, on the other hand, is bound to the phosphonate part of the ligand along with the [COO]− part of the ligand.

4. GROUP 13 PHOSPHONATES 4.1. Boron

All known borophosphonates are summarized in Table 3.65−69 Roesky et al.65 and Kuchen et al.66 prepared the first molecular borophosphonates in 1997. This followed the successful use of silanetriols in preparing metallasiloxanes of the type [{(Me2Ga)2(MeGa) 2}(RSiO3)2] [R = (2,6-i-Pr2C6H3)N(SiMe3)],67 which involve alkane elimination reactions (Figure 19).67 J


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Figure 19. A metallasiloxane [{(Me2Ga)2(MeGa)2}(RSiO3)2] [R = (2,6-i-Pr2−C6H3)N(SiMe3)].67 Adapted from ref 67. Copyright 1996 Wiley-VCH Verlag GmbH & Co. KGaA.

Scheme 13. Synthesis of the Tetranuclear Boron Phosphonate, [t-BuPO3BEt]465

Scheme 14. Synthesis of a Tetranuclear Borophosphonate Involving the Elimination of Trimethylsilyl Chloride66

Figure 20. Molecular structure of [PhBO3PBu-t]4.66 This compound possesses a distorted cubic D4R core, B4P4O12; boron and phosphorus atoms are present in alternate corners of the cube, while oxygen atoms occupy the edges of the cube. Adapted from ref 66. Copyright 1997 Wiley-VCH Verlag GmbH & Co. KGaA.

reported.76 This is a cationic complex where a central trinuclear cage has on either side of it a tetra-coordinate aluminum center (Scheme 17).76 Recently, Wen et al. reported a heterometallic decanuclear complex, [Al8Na2(HL)2(H2L)10(H2O)6]·20H2O (H4L = N,Ndimethylaminomethane-1,1-diphosphonic acid) (Figure 24).77 The novelty of the molecular structure of this complex is that it contains a central hexanuclear homometallic core, which is capped on either end by a sodium ion. Right on top of each sodium ion is another aluminum atom. Thus, the structure has a linear Al−Na−Na−Al array.

ensemble containing a central tetranuclear unit, on either side of which is a trinuclear motif. The connection between the subunits is achieved through Cs−F interactions involving a triangular cesium array and a fluoride ion (Figure 22).74 Another variant on the use of the fluoride ion as a structure directing agent involves the reaction of the mineral gibbsite, Al(OH)3, with 1-amino-1-methyl-ethylphosphonic acid in the presence of HF to afford the octanuclear derivative, [Al8F12{(CH3)2C(NH3)PO3}12] (Figure 23).75 All of the aluminum atoms are in the corners of the cube, while the 12 fluoride ions are present in the cube edges. The phosphonate ligand is involved in bridging alternate aluminum atoms. Recently, a pentanuclear aluminum phosphonate, [L4Al5Cl6(THF)6]·Cl (L = phthalimidomethyl) phosphonate, has been

4.3. Gallium

Table 5 contains a list of the known gallophosphonates. The nuclearity of molecular gallophosphonates varies from 1 to 11.82−88 In 1997, Roesky et. al reported the first examples of molecular gallophosphonates. A hexanuclear heterometallic derivative, Li4[(MeGa)6(μ3-O)2(t-BuPO3)6], was prepared in the reaction between tert-butylphosphonic acid and LiGaMe4 (Scheme 18).82 The molecular structure of this compound reveals the presence of two interconnected bowl-shaped trinuclear gallophosphonate motifs, {(t-BuPO3GaMe)3(μ3-O)}.82 K


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Table 4. Molecular Aluminum Phosphonates reactants

compounds

[t-BuPO3AlMe]4, AlMe3, n-Bu4NHF2, t-BuPO3H2 [PhPO3AlMe]4, n-Bu4NHF2, PhPO3H2, AlMe3 Al(NO3)3·9H2O, guanidine carbonate [(CH6N3)2CO3], KOH, [N-(phosphonomethyl) iminodiacetic acid] (NTAP) Al(NO3)3·9H2O, NH3, KOH, (NTAP) i-Bu3Al, t-BuPO3H2 AlMe3, MePO3H2 t-Bu3Al, MePO3H2 t-Bu3Al, t-BuPO3H2, [t-BuPO3AlMe]4, n-Bu4NHF2 [PhPO3AlMe]4, n-Bu4NHF2 Cs(i-Bu3AlF), t-BuPO3H2 t-Bu3Al, PhPO3H2 2-pyridylphosphonic acid (2-PypoH2), AlCl3·6H2O 4-pyridylphosphonic acid (4-PypoH2), AlCl3·6H2O 2-PypoH2, Al(NO3)3·9H2O phthalimidomethyl phosphonic acid (LH2), AlCl3 t-BuPO3H2, AlMe3, THF/n-hexane 1-amino-1-methyl-ethylphosphonic acid (AIPA), HF, Al(OH)3 (Ph3PMe)[VO2Cl2], AlCl3, t-BuPO3H2 N,N-dimethylaminomethane-1,1-diphosphonic acid [(CH3)2NCH(PO3H2)2] (H4L) Al(NO3)3·9H2O, 10% NaOH, H2O, 120 °C, 2 days NaAlEt2H2, t-BuPO3H2 Cs(i-Bu3AlF), t-BuPO3H2

ref

dinuclear -do-do-

73 73 78

(NH4)2[Al2(C5H6NPO7)2(H2O)2]·4H2O [t-BuPO3AlBu-i]4 [MeAlO3PMe]4 [t-BuAlO3PMe]4 [t-BuAlO3PBu-t]4 [t-BuPO3AlMe]4 [PhPO3AlMe]4 [i-BuAlO3PBu-t]4 [t-BuAlO3PPh]4 [(2-PypoH)4Al4(OH2)12]·Cl8·6H2O [(4-PypoH)4Al4(OH2)12]·Cl8·11H2O [(2-PypoH)4Al4(OH2)12]·(NO3)8·7H2O [L4Al5Cl6(THF)6]·Cl [MeAlO3PBu-t]6 [Al8F12{(CH3)2C(NH3)PO3}12] [ClAl{t-BuPO3}]10·H2O [Al8Na2(HL)2(H2L)10(H2O)6]3·20H2O

-dotetranuclear/cubic -do-do-do-do-do-do-do-do-do-dopentanuclear hexanuclear/D6R core tetranuclear/cubic decanuclear -do-

78 70 69 69 69 73 73 74 69 79 79 79 76 71 75 81 77

[Na3(THF)(t-BuPO3AlEt2)3]2

hexanuclear/single sixring (6R) heterometallic hexadecanuclear

80

[Cs3(THF)3F(i-BuAl)3(t-BuPO3)4]2 [(i-BuAl)2Al2(μ-F)2(t-BuPO3)4]

Figure 21. Tetranuclear D4R core of the aluminum phosphonate, [t-BuPO3AlBu-i]4.70 Adapted from ref 70. Copyright 1996 The Royal Society of Chemistry.

nuclearity/structure

[n-Bu4N]2[t-BuPO3AlF2]2 [n-Bu4N]2[PhPO3AlF2]2 (CH6N3)4[Al2(C5H6NPO7)2(OH)2]·8H2O

74

Figure 22. Molecular structure of [Cs 3 (THF) 3 F(i-BuAl) 3 (tBuPO3)4]2[(i-BuAl)2Al2(μ-F)2(t-BuPO3)4].74 For the sake of clarity, hydrogen atoms and THF molecules are omitted. Adapted from ref 74. Copyright 1998 Wiley-VCH Verlag GmbH & Co. KGaA.

The two trinuclear motifs sandwich a linear, one-dimensional lithium wire consisting of four lithium ions (Scheme 18), which are bound by the oxygen atoms of the phosphonate ligand. Interestingly, Li4[(MeGa)6(μ3-O)2(t-BuPO3)6] is extremely stable and does not undergo hydrolysis even at 70 °C. However, treatment of Li4[(MeGa)6(μ3-O)2(t-BuPO3)6] with 12-crown-4 ether followed by D2O leads to the formation of the tetranuclear compound [t-BuPO3GaMe]4 possessing a D4R core (Scheme 18).82 Interestingly, a tetranuclear compound [t-BuGaO3PBu-t]4 can also be prepared in a direct reaction involving t-Bu3Ga and t-BuPO3H2 (Table 5).83 In an analogous reaction between t-Bu3Ga with PhPO3H2, a dinuclear compound was isolated (Scheme 19).83 An interesting octanuclear derivative, [(2-PypoH)2(2-Pypo)4Ga8Cl12(OH2) 4(THF) 2]· (NO3)2·9THF (2-PypoH2 = 2-pyridylphosphonic acid), was

prepared by reacting 2-pyridylphosphonic acid with GaCl3 and Ga(NO3)3 (Scheme 20).79 The molecular structure of the latter reveals a central tetranuclear core attached to four peripheral GaCl3 units. 4.4. Indium

In 2012, a one-dimensional polymeric indium phosphonate was reported for the first time (Figure 25).76 In 2013, our group reported the first examples of molecular indium phosphonates (Schemes 21 and 22).89 We were able to prepare both di- and trinuclear derivatives utilizing solvothermal reactions. The reaction of InCl3 with t-BuP(O)(OH)2 in the presence of 1,10-phenanthroline (phen) afforded the dinuclear derivative (Scheme 21) where the two indium centers are bridged by the L


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Scheme 16. Synthesis of a Dinuclear Aluminum Phosphonate, [n-Bu4N]2[PhPO3AlF2]273

Scheme 17. Synthesis of a Pentanuclear Aluminum Phosphonate, [L4Al5Cl6(THF)6]Cl (L = Phthalimidomethyl)76

Figure 23. An octanuclear core of [Al8F12{(CH3)2C(NH3)PO3}12].75 Adapted from ref 75. Copyright 2006 American Chemical Society.

Figure 24. Decanuclear core of a heterometallic complex, [Al8Na2(HL)2(H2L)10(H2O)6] (H4L = N,N-dimethylaminomethane1,1-diphosphonic acid).77 Adapted from ref 77. Copyright 2009 American Chemical Society.

A small variation in the reaction conditions involving a change of reactants, In(NO3)3 and cyclopentylphosphonic acid, leads to the formation of a trinuclear derivative (Scheme 22).89 In this case, both [RPO3]2− and [RP(OH)(O)2]− ligands are involved in holding the ensemble together; the former bridges three indium centers, while the latter bridges two. As in the case of the dinuclear derivative, two terminal [RP(OH)(O)2]− ligands are present; the third indium center does not possess any.89

Scheme 15. A Hexanuclear Aluminum Phosphonate, [MeAlO3PBu-t]6, Possessing a D6R Core71

5. GROUP 14 PHOSPHONATES 5.1. Tin

Organostannoxanes have a very rich structural chemistry. Many different types of structural forms have been isolated utilizing either carboxylate, phosphinate, or sulfonate ligands. For example, the 1:1 reaction of [n-BuSn(O)(OH)]n with FcC(O)OH [Fc = ferrocenyl] afforded a hexameric derivative [n-BuSn(O)OC(O)Fc]6 , which possesses a drum type structure (Scheme 23).90 This approach has been subsequently utilized to prepare organostannoxanes that contain functional peripheries that are photochemically, electrochemically, or catalytically active.90−94 Other structural forms that have been isolated include the O-capped cluster, double-O-capped cluster, butterfly cluster, cube, extended cage, drum, ladder, crown cluster, and football cages. Representative examples are

monoanionic [t-BuP(OH)(O)2]− ligand. Each indium also is bound to one terminal [t-BuP(OH)(O)2]− ligand. The phenanthroline ligands effectively block the coordination sites on the indium center and prevent the formation of coordination polymers.89 M


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Table 5. Molecular Gallophosphonates reactants t-Bu3Ga, HPO3H2 [t-BuPO3GaMe]4, n-Bu4NHF2 t-Bu3Ga, PhPO3H2 t-Bu3Ga, MePO3H2 t-Bu3Ga, t-BuPO3H2 t-Bu3Ga, PhPO3H2 t-Bu3Ga, PhPO3H2 t-Bu3Ga, t-BuPO3H2

compounds

2-pyridylphosphonic acid (2-PypoH2), GaCl3, Ga(NO3)3·xH2O t-BuPO3H2, LiGaMe4

[t-Bu2GaO2P(OH)H] [n-Bu4N][MeGa{t-BuPO2(OH)}3] [t-Bu2Ga(μ2-O2P(OH)Ph)]2 [t-Bu2GaO2P(OH)Me]2 [t-Bu2GaO2P(OH)Bu-t]2 [t-Bu2GaO2P(OH)Ph]2 [t-Bu2Ga{μ-O2P(Ph)OGaBu-t2)] [(t-BuGa)2(t-Bu2Ga)(μ3-O3PBu-t)2 (μ2-O2P(OH) Bu-t)] t-Bu7Ga3P3O8(OH) [Na4(μ2-OH2)2(THF)2][(Me2GaO3PBu-t)2]2· 2THF [t-BuGaO3PMe]4 [t-BuGaO3PPh]4 [t-BuGaO3PBu-t]4 [t-BuGa(μ3-O3PPh)]4 [(2-PypoH)2(2-Pypo)4Ga8Cl12(OH2)4(THF)2]· (GaCl4)2·8THF [(2-PypoH)2(2-Pypo)4Ga8Cl12(OH2)4(THF)2]· (NO3)2·9THF Li4[(MeGa)6(μ3-O)2(t-BuPO3)6]·(THF)4

t-BuPO3H2, KGaMe4

[K(THF)6][K5(THF)2{(Me2GaO3 PBu-t)2}3]

t-BuPO3H2, t-Bu3Ga t-BuPO3H2, NaGaMe4 t-Bu3Ga, MePO3H2 t-Bu3Ga, PhPO3H2 t-Bu3Ga, t-BuPO3H2 t-Bu3Ga, PhPO3H2 2-pyridylphosphonic acid (2-PypoH2), GaCl3

Scheme 18. Synthesis of the Ga6 Phosphonate, Li4[(MeGa)6(μ3-O)2(t-BuPO3)6]·(THF)4, and Its Conversion to a Tetranuclear Derivative, [t-BuPO3GaMe]482


ref

mononuclear -dodinuclear, eight-membered ring -do-do-do-dotrinuclear

83 84 85 83 83 83 86 83

-dotetranuclear

87 88

tetranuclear/cubic core -do-do-dooctanuclear

83 83 83 85 79

-do-

79

hxanuclear; lithium ions arranged in a one-dimensional wire heterometallic undecanuclear

82 88

Scheme 19. Synthesis of a Dinuclear Gallophosphonate, [t-Bu2GaO2P(OH)Ph]283

Scheme 20. Preparation of an Octanuclear Gallophosphonate, [(2-PypoH)2(2-Pypo)4Ga8Cl12(OH2)4(THF)2]·(NO3)2·9THF (2-PypoH2 = 2-Pyridylphosphonic Acid)79

illustrated in Figure 26.95−105 All of these were isolated by the reaction of organotin chlorides, -oxides, -hydroxides, and -oxide-hydroxides with protic acids (Schemes 24−28). In comparison to organotin carboxylates, -phosphinates, and -sulfonates, the corresponding phosphonates are still quite

sparse. Holmes et al. have reported the first example of a monoorganotin phosphonate cage, [{(n-BuSn)2(μ-O){O2P(OH)Bu-t}4]2, in the reaction of [n-BuSn(O)OH]n with t-BuP(O)(OH)2.106 The crystal structures reveal that two N


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Figure 25. An indium(III) phosphonate coordination polymer [{(LH)In(H2O)}(H2O)2(ClO4)]n [LH2 = (N-phthalimidomethyl) phosphonic acid].76 Adapted from ref 76. Copyright 2012 The Royal Society of Chemistry.

Scheme 21. Synthesis of a Dinuclear InIII Phosphonate, [In2(t-BuPO3H)4(phen)2Cl2] [phen = 1,10-Phenanthroline]89

Scheme 23. Synthesis of a Hexanuclear Organostannoxane, [{n-BuSn(O)OC(O)Fc}6], Possessing a Drum Structure90

Scheme 22. Synthesis of a Trinuclear InIII Phosphonate, [In3(C5H9PO3)2(C5H9PO3H)4(phen)3]·NO3·3.5H2O89

of organotin substrates and phosphinic acids. In a reaction involving [n-BuSn(O)OH]n and (OPh)2P(O)H, it was found that the P−OPh bond undergoes a cleavage, generating the [HPO3]2− ligand, in situ (Scheme 26).109 Two such ligands are involved in a bridging coordination action to stitch two O-capped clusters together affording a double O-capped cluster, [{(n-BuSn)3(PhO)3O}2{HPO3}4].109 A remarkable structural resemblance exists between the double O-capped cluster and the dodecanuclear organostannoxane football cage. Both of these compounds contain two peripheral tritin motifs. In the double O-capped cluster, the connection is achieved through the phosphonate ligands. In the football cage, the connection is achieved through a Sn6O6 motif. A hexatin phosphate, [(PhSn) 6 (μ-OH) 2 (μ 3 -O) 2 (μ-OEt)4{(ArO)PO3}4] (Ar = 2,6-i-Pr2−C6H3), was isolated more recently, where the phosphate unit, [ArOPO3]2−, is also bound to three tin centers.110 More recently, another double O-capped cluster was isolated in a solvothermal reaction involving [n-BuSn(O)OH]n and PhPO3H2.111 In addition to the tetra- and hexanuclear organotin phosphonates described above, a couple of dinuclear phosphonates are also known. Ribot et al. were able to isolate a dinuclear derivative, [n-Bu2Sn{(HO)(O)2PMe}2]2, in the reaction between [n-Bu2SnO]n and MePO3H2 (Scheme 27).112 This compound possesses a puckered eight-membered Sn2P2O4 core where two tin centers are bridged by two [MeP(O)2(OH)]− ligands. Additionally, each tin center is also bound by a terminal [MeP(O)2(OH)]− ligand.112 The reaction of [n-Bu2SnO]n with 6-phosphono-pyridine2-carboxylic acid (LH3) (Scheme 28) afforded a dinuclear

dimeric Sn−O−Sn units are bridged on each side by two isobidentate [t-BuP(OH)O2]− ligands. A similar type of structural form was isolated by Chandrasekhar et al. in the reaction of n-BuSn(OH)2Cl with t-BuPO3H2 (Scheme 24).107 Interestingly, another example of a tetranuclear cyclic organotin phosphonate cage, [{(BzSn) 2 (μ-O)}{O 2 P(OH)Bu-t} 4 ] 2 (Bz = benzyl), was prepared by the cleavage of the Sn−C bond, involving the reaction between dibenzyltin dichloride, tribenzyltin chloride, or dibenzyltin oxide with t-BuPO3H2.108 This reaction was shown to initially proceed through a dinuclear organotin phosphonate, which subsequently dimerizes, under refluxing conditions, to the tetranuclear derivative (Scheme 25).108 O-Capped clusters are ubiquitous in organostannoxane chemistry and are accessible from reactions involving a variety O


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Figure 26. Representative examples of organostannoxane clusters.95−105

layered PbII phosphonate ensemble, [Pb5(O3PCH2CH2CO2)2(O3PCH2CH2CO2H)2]n, is shown in Figure 27.116 This compound was prepared in the reaction of Pb(O2CCH3)2· 3H2O, carboxyethylphosphonic acid, and NaOH under hydrothermal conditions.

Scheme 24. Synthesis of a Tetranuclear Tin Phosphonate, [(n-BuSn)2O{O2(OH)PBu-t}4]2107

6. GROUP 15 PHOSPHONATES 6.1. Antimony

Organoantimony phosphonates are very few. The reaction of p-chlorophenylstibonic acid (ArSbO3H2) and t-butylphosphonic acid (t-BuPO3H2) was shown to afford a dinuclear compound, which contained a Sb−O−Sb motif that was bridged by two [t-BuPO2(OH)]− ligands (Scheme 29). Each antimony center further carried two monodentate [t-BuPO2(OH)]− ligands.117 A variation of the reaction conditions afforded tetranuclear derivatives [(SbAr)4O2(O3PPh)4(HO3PPh)4] where the two dinuclear units are bridged by four [PhPO3]2− ligands (Scheme 30).118 Notice the resemblance of the dimeric motif with that found in [{(BzSn)2(μ-O)}{O2P(OH)Bu-t}4]2.108 Each of the phosphonate group binds to the Sb center through two oxygen atoms in a bridging fashion; the remaining oxygen atom is involved in the formation of a H-bond. Heterometallic antimony complexes containing CoII, CuII, and LiI have recently been prepared (Figures 28 and 29).

compound.113 The role of the phosphonate is to provide a chelating coordination motif in conjunction with a pyridyl nitrogen atom. In general, in most organostannoxanes the coordination number around tin is six. In this example, tin is seven-coordinate in a distorted pentagonal bipyramidal geometry. Table 6 summarizes the known tin phosphonates.90−115 5.2. Lead

To the best of our knowledge, there are no reports of molecular lead(II) phosphonate complexes. All of the reported lead phosphonates possess extended structures. A representative P


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Scheme 25. Debenzylation Reactions Affording the Tetranuclear Organotinphosphonate, [{(BzSn)2(μ-O)}{O2P(OH)Bu-t}4]2, via the Dinuclear Compound, [(BzSn(μ-O){O2P(OH)Bu-t}2]2108

Scheme 26. Synthesis of a Double O-Capped [{(n-BuSn)3(PhO)3O}2{HPO3}4] Cluster109

Scheme 28. Synthesis of a Dinuclear Diorganotin Phosphonate, [n-Bu2SnLH]2113a

a

The tin centers are seven-coordinate.

heterometallic CoII2Sb4 cluster [Co2(SbAr)4O4(O3PPh)4(OMe)4py2].118 This compound possesses a cube-type core (Sb4P2Co2) with the antimony, phosphorus, and cobalt atoms occupying the corners of the cube, while the oxygen atoms of the phosphonate ligands are involved in a 3.111 coordination binding mode involving the face of the cubes (Figure 29).118 Details about the known antimony phosphonates are summarized in Table 7.117−122 It must be mentioned in passing that stibonic acids, RSbO3H2, which are used as precursors in organoantimony chemistry, are poorly characterized compounds, because of their aggregation behavior in the solid state. Recently, utilizing steric bulky ligands, a well-defined stibonic acid, [2,6Mes2C6H3Sb(O)(OH)2]2 (Mes = 2,4,6-Me3C6H2), was obtained, which contains a Sb2O2 four-membered ring (Figure 30).119 Although the reactions of this compound have not been studied well, it is hoped that such soluble precursors can be utilized to explore the organoantimony chemistry in the future.

Scheme 27. Synthesis of a Dinuclear Diorganotin Phosphonate, [n-Bu2Sn{(HO)(O)2PMe}2]2112

A heterometallic CoII2Sb2 cage, [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2], was synthesized in the reaction involving [(SbAr)2O(HO3PBu-t)6], Co(OAc)2·4H2O, and pyridine (Figure 28).118 In this cage, two cobalt and two antimony atoms are arranged in a distorted tetrahedral geometry where the three faces of the tetrahedron are capped by three [t-BuPO3]2− ligands, while the remaining faces contain two bridging oxide and two methoxide ligands. The reaction of the tetranuclear antimony cage [(SbAr)4O2(PhPO3H)4(PhPO3)4] with Co(OAc)2·4H2O and pyridine under solvothermal conditions afforded a hexanuclear

6.2. Bismuth

Unlike tin and antimony, but more similar to aluminum and gallium, bismuth phosphonates are accessed in reactions involving Bi−C bond cleavage. Thus, the reaction of triphenylbismuth and t-BuPO3H2 afforded [(t-BuPO3)10(t-BuPO3H)2Bi14O10·3C6H6· 4H2O].123 The formation of this compound involves the complete cleavage of Bi−C bonds. The structure of this compound contains 14 Bi atoms: four each in the periphery and six in the Q


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Table 6. Molecular Tin Phosphonates reactants [n-Bu2SnO]n, MePO3H2 6-phosphono-pyridine-2-carboxylic acid (LH3), n-Bu2SnO [n-BuSn(O)OH]n, EtPO3H2 [MeSn(O)OH]n, t-BuPO3H2 [n-BuSn(O)OH]n, t-BuPO3H2 n-BuSn(OH)2Cl, t-BuPO3H2 (PhCH2)2SnCl2/(PhCH2)2SnO·H2O/(PhCH2)3SnCl, t-BuPO3H2 [n-BuSn(O)OH]n, PhPO3H2 [n-BuSnO(OH)], (PhO)2P(O)H, PhOH, H3PO3 RSnCl3 [R = 2-(phenylazo)phenyl], t-BuPO3H2 RSnCl3 [R = 2-(phenylazo)phenyl], C6H11PO3H2 [n-BuSn(O)(OH)]n, H3PO3, HOC6H4-4-X (X = H, Cl, Br, I) Bz3SnCl (Bz = benzyl), PhPO3HNa, NaOH


ref

[n-Bu2Sn(HO3PMe)2]2 [n-Bu2SnLH]2 [(n-Bu)2Sn2O{O2(OH)PEt}4]2 [Me2Sn2O{O2(OH)PBu-t}4]2 [(n-Bu)2Sn2O{O2(OH)PBu-t}4]2 [(n-BuSn)2O{O2(OH)PBu-t}4]2 [(PhCH2)2Sn2O(O2P(OH)Bu-t)4]2

compounds

dinuclear/eight-membered ring -dohexanuclear/double-O-capped cluster -do-do-do-do-

112 113 106 106 106 107 108

[{(n-BuSn)3(MeO)3O}2(O3PPh)4]·MeOH [{(n-BuSn)3(PhO)3O}2{HPO3}4] [(RSn)6(μ-OH)6(μ3-O)2(t-BuPO3)4]·5THF [(RSn)6(μ-OH)6(μ3-O)2 (C6H11PO3)4]·THF {[(n-BuSn)3(μ3-O)(OC6H4-4-X)3]2[HPO3]4}

-do-do-do-do-do-

111 109 106 106 114

[Na6(CH3OH)2(H2O)][{(BzSn)3 (PhPO3)5(μ3-O) (CH3O)}2Bz2Sn]·CH3OH

heptanuclear

115

Figure 27. A layered PbII phosphonate, [Pb5(O3PCH2CH2CO2)2(O3PCH2CH2CO2H)2]n.116 Adapted from ref 116. Copyright 2004 Elsevier Masson SAS.

Scheme 29. Synthesis of a Dinuclear Antimony Phosphonate, [(SbAr)2O(HO3PBu-t)6]117

Scheme 30. Synthesis of a Tetranuclear Antimony Phosphonate, [(SbAr)4O2(O3PPh)4(HO3PPh)4]118

center. All of the bismuth atoms are stitched together by the coordination of 10 [t-BuPO3]2− and two [t-BuPO3H]− ligands. In addition, 14 O2− ligands are involved in holding the ensemble together (Scheme 31).123 Recently, we prepared a similar type of bismuth-oxo-phosphate cluster, [{(ArO)PO 3 } 10 {(ArO)PO2OH}2(Bi14O10)·2(CH3OH)] (Ar = 2,6-i-Pr2−C6H3), involving the reaction of the phosphate monoester {(ArO)PO(OH)2} (Ar = 2,6-i-Pr2−C6H3) and BiPh3.124 Interestingly, a mononuclear bismuth phosphonate, LBi[O2(OH)PBu-t]2, L = [2,6- (Me2NCH2)2C6H3]−, was recently prepared using a N−C−N pincer type of ligand (Figure 31).121 A trinuclear bismuth phosphonate was recently prepared in the reaction of [LBiO]2, L = [2,6-(Me2NCH2)2C6H3]−, and t-BuPO3H2. The molecular structure reveals a 12-membered

ring containing alternate chelating and bridging binding modes of the [t-BuPO3]2− ligand (Figure 32).121 All of the molecular bismuth phosphonates are listed in Table 8.121,123−125 6.3. Tellurium

There are no reports on molecular tellurium phosphonates. A few molecular tellurium phosphinates are, however, known. Recently, it has been shown by us that the reaction R


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[(Cp*TiO 3 PPh) 4 (μ-O) 2 ] and [(Cp*Ti) 3 (t-BuPO 3 ) 2 {t-BuPO2(OH)}(μ-O)2] were prepared by the reaction of Cp*TiMe3 with PhPO3H2 or t-BuPO3H2 (Scheme 33). These reactions involve Ti−C bond cleavage involving the Ti−CH3 groups. The molecular structures of these tetranuclear complexes are similar to those of the other cuboidal derivatives such as [t-BuPO3BEt]4 described above.65 One notable difference, however, is the presence of two Ti−O−Ti linkages on the two opposite faces of the cube (Figure 33). A reaction of Cp*TiCl3 with MePO3H2 in the presence of the hydrogen chloride scavenger, Et3N, also affords a similar tetranuclear cage, [(Cp*TiO3PMe)4(μ-O)2].127 A variation of the phosphonic acid, involving t-BuPO3H2, afforded the trinuclear derivative [(Cp*Ti)3(t-BuPO3)2{tBuPO2(OH)}(μ-O)2].127 In this case, three titanium atoms in a planar array are capped on the top and the bottom by two [t-BuPO3]2− ligands, while the equatorial plane is stiched by a [t-BuP(OH)O2]− ligand (Scheme 34).127 A structurally different tetranuclear derivative, [Ti4(μ3O)(OPr-i)5(μ-OPr-i)3(PhPO3)3]·DMSO, was prepared in the reaction of Ti(OPr-i)4 with PhPO3H2 (Scheme 35).128 In this compound, a [Ti3(μ3-O)] motif is capped by a titanium alkoxide unit [Ti(OPr-i)3]. The titanium centers are linked to each other through phosphonate and alkoxide linkages. Interestingly, in a similar reaction of Ti(OPr-i)4, but involving Ph2P(O)(OH) instead of PhPO3H2, a tetranuclear compound, [Ti(μ3-O)(OPr-i)(Ph2PO2)]4, was obtained (Scheme 36).128 An interesting dinuclear derivative, [n-Bu 4 N] 2 [{Ti(OMe)3(O3PPh)}2], was obtained in the reaction of [nBu4N][PhPO3H] and Ti(OMe)4 (Scheme 37).129 In this compound, the dinuclear core is established through the bridging coordination of two μ-methoxy groups. The A-frame type structure is completed by the bridging coordination action of [PhP(O)(O)2]2− ligands on either side of the dinuclear core. Interestingly, an analogous NbV compound, [n-Bu4N]2[{Nb(OMe)3(O3PPh)}2(μ-O)], has also been prepared involving the reaction of niobium methoxide and [n-Bu4N][PhPO3H].129 A dinuclear derivative containing only bridging phosphonate ligands, [{Ti(C5Me4Et)(μ-O2P(OH)Me)(μ-O2P(O)Me)}2], was obtained in the reaction of (C5Me4Et)TiF3 and MeP(O)(OSiMe3)2 in the presence of water (Figure 34).130 The driving force of the reaction is the facile liberation of Me3SiF and Me3SiOH. While two of the phosphonate ligands are fully deprotonated, the other two have one free −OH group. As a result, intramolecular hydrogen bonding between such units occurs within the molecule. In addition to exploring reactions with the native phosphonic acid, there have been efforts to utilize the milder and cleaner reactivity of the corresponding silylated derivatives. Thus, the reaction of Ti(OPr-i)4 with bis(trimethylsilyl)phosphonates has been explored. In reactions where no additional carboxylic acid was used, tetra-, hepta-, and octanuclear compounds were isolated (Figures 35).131 In all of these, the trimeric motif [Ti3(μ3-O)(μ2-OPr-i)3(OPr-i)3(O3PR3)] is present. In the tetranuclear derivatives, the trimeric motif is capped by a Ti(OPr-i)2 unit. In the heptanuclear derivative, two trimeric motifs are linked through a central titanium (Figure 36).131 In the octanuclear deivative, two Ti4 units are bridged by isopropyl phosphonate ligands (Figure 37).131 Interestingly, the reaction involving the bulky ligand, [NaphthylCH2PO3]2−, afforded only the tetranuclear drivative, Ti4(OPr-i)8(O3PCH2Naphthyl)4.131 A variation of the above reaction involving small amounts of acetic acid leads to a different result leading to the formation

Figure 28. Molecular structure of the Co2Sb2 phosphonate, [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2].118 Adapted from ref 118. Copyright 2008 The Royal Society of Chemistry.

Figure 29. Molecular structure of a Co 2 Sb 4 phosphonate, [Co2(SbAr)4O4(O3PPh)4(OMe)4py2].118 Adapted from ref 118. Copyright 2008 The Royal Society of Chemistry.

of 1,1,2,3,3-pentamethyltrimethylenephosphinic acid [cycP(O)OH] and (C6H11)2P(O)OH with monoorganotellurium trichloride RTeCl3 (R = 2-phenylazophenyl) afforded two pentanuclear tellurium phosphinate clusters, [(RTe)4(TeO)(μ-O)6(cycPO2)2]· THF [cycPO2 = 1,1,2,3,3-pentamethylene phosphinate] and [(RTe)4(TeO)(μ-O)6{(C6H11)2PO2}2]·2C6H6. Both of the complexes are formed through Te−C bond cleavage reactions. These complexes are isostructural and contain a Te4P2O6 macrocyclic framework, which is part of a Te5O11P2 multimetallacyclic framework. Both of these complexes contain a central TeO unit that is connected to four other tellurium centers through four μ-O bridges (Scheme 32).126

7. GROUP 4 PHOSPHONATES 7.1. Titanium

The nuclearity of molecular titanium phosphonates varies from 2 to 26.127−137 The first soluble molecular TiIV phosphonate was reported by Roesky et al. in 1998.127 The compounds S


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Table 7. Molecular Antimony Phosphonates reactants [2,6-(Me2NCH2)2C6H3SbO]2, t-BuPO3H2 [2,6-(Me2NCH2)2C6H3SbO]2, PhPO3H2 [2,6-(Me2NCH2)2C6H3SbO]2, H3PO3 p-chlorophenylstibonic acid (ArSbO3H2), t-BuPO3H2 ArSbO3H2, t-BuPO3H2 ArSbO3H2, PhPO3H2 [(SbAr)2O(HO3PBu-t)6], LiOMe/pyridine, Co(OAc)2·4H2O ArSbO3H2, t-BuPO3H2, LiOMe/pyridine, Co(OAc)2·4H2O p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, t-BuPO3H2 Co(OAc)2·4H2O, ArSbO3H2, PhPO3H2, LiOMe/pyridine [(SbAr)4O2(PhPO3H)4(PhPO3)4], pyridine, Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], Co(OAc)2·4H2O, 3-picoline [(SbAr)4O2(PhPO3H)4(PhPO3)4], Co(OAc)2·4H2O, 4-picoline [(SbAr)4O2(PhPO3H)4(PhPO3)4], quinoline (C9H7N), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 1,2-diazole (C3H4N2), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 4-phenylpyridine (C11H9N), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 2,6-lutidine (C7H9N), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 2-picoline, Co(OAc)2·4H2O p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, t-BuPO3H2 [(SbAr)4O2(PhPO3H)4(PhPO3)4], pyridine, Co(OAc)2·4H2O ArSbO3H2, PhPO3H2, pyridine, Co(OAc)2·4H2O p-chlorophenylstibonic acid (ArSbO3H2), t-BuPO3H2, Cu(OAc)2· 4H2O, lutidine p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, LiOMe, t-BuPO3H2


ref

2,6-(Me2NCH2)2C6H3Sb[OP(O)(OH)Bu-t]2 2,6-(Me2NCH2)2C6H3Sb[OP(O)(OH)Ph]2 [2,6-(Me2NCH2)2C6H3Sb{O2P(H)(O)}]2 [(SbAr)2O(HO3PBu-t)6] [(SbAr)2(HO3PBu-t)6O] [(SbAr)4O2(O3PPh)4(HO3PPh)4] [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2] [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2] [Cu3O4(SbAr)2(O3PBu-t)4(py)3]

compounds

mononuclear -do-dodinuclear/eight-membered ring -dodouble-O-capped heterometallic tetranuclear; Co2Sb2 -doheterometallic pentanuclear; Cu3Sb2

121 121 122 117 118 118 120 118 117

[Co2(SbAr)4O4(O3PPh)4(OMe)4py2] [Co2(SbAr)4O4(O3PPh)4(OMe)4py2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(3-picoline)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4 (4-picoline)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(C9H7N)2]

heterometallic hexanuclear; Co2Sb4 -do-do-do-do-

118 120 120 120 120

[Co2(SbAr)4O4(O3PPh)4(OMe)4(C3H4N2)2]

-do-

120

[Co2(SbAr)4O4(O3PPh)4(OMe)4(C11H9N)2]

-do-

120

[Co2(SbAr)4O4(O3PPh)4(OMe)4(C7H9N)2]

-do-

120

[Co2(SbAr)4O4(O3PPh)4(OMe)4(MeOH)2] [Cu4O2(SbAr)2(O3PBu-t)2(O2CMe)2(OMe)6]

-doheterometallic hexanuclear; Cu4Sb2

25 117

[Co4(SbAr)5O9(O3PPh)6(py)4] [Co4(SbAr)5O9(O3PPh)6(py)4] [Cu8O4(SbAr)2(O3PBu-t)6(O2CMe)4(lutidine)2]

heterometallic nonanuclear; Co4Sb5 120 -do118 heterometallic decanuclear; Cu8Sb2 117

[Cu5Li4O6(SbAr)4(O3PBu-t)6 (O2CMe)2(OMe)4(MeOH)4]

heterometallic tridecanuclear; Cu5Sb4Li4

117

Figure 30. A stibonic acid, [2,6-Mes 2 C 6 H 3 Sb(O)(OH) 2 ] 2 (Mes = 2,4,6-Me3C6H2).119

Scheme 31. Synthesis of a Molecular Bi14 Phosphonate, [(t-BuPO3)10(t-BuPO3H)2Bi14O10·3C6H6·4H2O]123

Figure 31. A mononuclear BiIII phosphonate, LBi[O2(OH)PBu-t]2, L = [2,6-(Me2NCH2)2C6H3]−.121

(OAc = acetate) (Figures 38 and 39).132 In these reactions, in situ generation of water can occur through various possibilities. Thus, for example, the reaction of alcohol with either coordinated or noncoordinated phosphonic acids leads to ester formation along with water. Similarly, acetic acid reacts with phosphonic acid affording a phosphonate ester and water. The water thus generated leads to partial hydrolysis of the products resulting in the formation of oxo/alkoxo cluster. The hexanuclear derivative possesses a Ti6O4 core containing two Ti3O motifs that are connected to each other by μ-oxo and μ3-phosphonato bridges. Notice the prevalence of the Ti3O units in many of the titanium oxo-alkoxo clusters.73,133,134 All of the known titanium phosphonates are listed in Table 9. 127−137

of hexa- and pentanuclear derivatives, [Ti6O4(OPr-i)10(OAc)2(O3P-allyl)2] and [Ti5O(OPr-i)11(OAc)(O3PCH2CH2CH2Br)3] T


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Review

Scheme 32. Synthesis of Tellurium Phosphinates, [(RTe)4(TeO)(μ-O)6(cycPO2)2]·THF [cycPO2 = 1,1,2,3,3Pentamethylene Phosphinate] and [(RTe)4(TeO)(μ-O)6{(C6H11)2PO2}2]·2C6H6 (R = 2-Phenylazophenyl)126

Figure 32. A trinuclear 12-membered bimuth phosphonate, [LBiO3PBu-t]3, L = [2,6-(Me2NCH2)2C6H3]−.121 Adapted from ref 121. Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

7.2. Zirconium and Hafnium

Molecular phosphonates of ZrIV and HfIV are nonexistent. ZrIV phosphonates possessing extended structures are known: (NH4)Zr[F]2[H3{O3PCH2NH(CH2CO2)2}2]·3H2O·NH4Cl138 and [Zr 2 (PO 4 ){O 3 PCH 2 N(CH 2 CO 2 H) 2 }(O 3 PCH 2 N(CH2CO2H)(CH2CO2)}(H2O)2].139 Interestingly, two structural forms of zirconium phosphinates/phosphates are known. Here again, there are no corresponding hafnium derivatives. The reaction of Cp2ZrCl2 with 1 equiv of (OR′)2P(O)(OH) or R′R″P(O)(OH) afforded trinuclear derivatives, [{(η5-C5H5)Zr}3(μ3-O)(μ2-OH)3{(PhO)2PO2}3]·Cl, {[{(η5-C5H5)Zr}3(μ3O)(μ2-OH)3{(PhCH2O)2PO2}3]·Cl, and [{(η5-C5H5) Zr}3(μ3O)(μ 2 -OH) 3 {Ph(CH 3 )PO 2 } 3 ]·Cl (Scheme 38). 140 The molecular structures of these compounds very closely resemble the O-capped cluster motifs described in the section on tin95−105 phosphonates and consist of an incomplete cube with four vertices occupied by oxide ions and three by zirconium. Alternate pairs of zirconium centers are bridged by the [R′R″PO2]− ligands. Changing the stoichiometry of the reaction (with an increase in the phosphinic acid) leads to the formation of a dinuclear compound with a Zr2O2 core (Scheme 39). The two Zr centers are bridged by two [R′R″PO2]− ligands. Each zirconium center also has a terminal [R′R″PO2]− ligand.140 Another interesting alkoxide-bridged dinuclear zirconium phosphinate cage, [(OPr-i) 3Zr(μ-OPr-i) 2 (μ-OPOPh 2 )Zr(OPr-i)2Ph2P(O)(OH)], was obtained in the reaction of [Zr(OPr-i)4(i-PrOH)]2 with Ph2P(O)(OH) (Scheme 40).141

Scheme 33. Synthesis of the Ti4 Phosphonate Complex [(Cp*TiO3PPh)4(μ-O)2]127

The molecular structure of this compound reveals the presence of a four-membered Zr2O2 core. The two zirconium centers are bridged by a phosphinate ligand. In addition, one of the zirconium centers is bound to a monodentate phosphinate ligand.

8. GROUP 5 PHOSPHONATES 8.1. Vanadium

Among vanadium phosphonates, those containing homovalent VIV and mixed valent VIV/VV are more prevalent.143,150,154 This

Table 8. Molecular Bismuth Phosphonates reactants

compounds

1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene phosphonic acid (H8DOTMP), Bi2O3, HNO3, NaOH H8DOTMP, Bi2O3, HNO3, NaNO3, NaOH [LBiO]2, L = [2,6-(Me2NCH2)2C6H3]−, t-BuPO3H2 [LBiO]2, t-BuPO3H2 Ph3Bi, t-BuPO3H2 U


ref

[Bi(H5O2)(H4DOTMP)]

mononuclear

125

[Bi(H4DOTMP)(Na(H2O)4)] LBi[O2(OH)PBu-t]2 [LBiO3PBu-t]3 [(t-BuPO3)10(t-BuPO3H)2Bi14O10· 3C6H6·4H2O]

-do125 -do121 trinuclear; 12-membered ring 121 tetradecanuclear 123


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Review

Scheme 36. Synthesis of [Ti(μ3-O)(OPr-i)(Ph2PO2)]4 Containing a Tetranuclear Cubane Core128

Scheme 37. Synthesis of a Dinuclear Titanium Phosphonate, [n-Bu4N]2[{Ti(OMe)3(O3PPh)}2]129

Figure 33. A tetranuclear TiIV phosphonate cage, [(Cp*TiO3PPh)4(μ-O)2], containing Ti−O−Ti linkages.127 Adapted from ref 127. Copyright 1998 American Chemical Society.

Scheme 34. Synthesis of a Planar Trinuclear Titanium Phosphonate Cage [(Cp*Ti)3(t-BuPO3)2{t-BuPO2(OH)}(μ-O)2]127

Scheme 35. Synthesis of [Ti4(μ3-O)(OPr-i)5(μ-OPri)3(PhPO3)3]·DMSO128

Figure 34. A dinuclear titanium phosphonate cage [{Ti(C5Me4Et)(μ-O2P(OH)Me)(μ-O2P(O)Me)}2].130 Adapted from ref 130. Copyright 2008 Elsevier Masson SAS.

(Scheme 41).142 The molecular structure of this compound contains a distorted tetrahedron of VIII centers bound to a central μ4-oxide. Each face of the tetrahedron is capped by the phosphonate ligand, which binds in a 3.111 mode. The opposite edges of the tetrahedron consist of a μ-OH.142 A variation of the chemistry, involving [t-BuPO3]2−, afforded a pentanuclear compound, [VIII5(μ3-OH)(O3PBu-t)6Cl2(Py)6] where the VIII sites lie on the vertices of a trigonal bipyramid.142 Here also, the [t-BuPO3]2− ligands cap the triangular faces. The VIII centers present in the equatorial position are bound together by a μ3-OH (Figure 40).142 Addition of pivalic acid to the reaction afforded the hexanuclear compound, [VIII6(μ3-O)2(O2CBu-t)8(HO2CBu-t)2(HO3PBu-t)2(O3PBu-t)2].142 In this compound, two oxo-centered

chemistry is dominated by the presence of the VO moiety. Many such compounds have been used in oxidation catalysis.143,154 Also, many such oxovanadium phosphonates have a varied topology and serve as hosts for encapsulating both anionic and cationic guests.143,154 In comparison to high-valent oxovanadium phosphonates, those containing low-valent vanadium(III) phosphonates are less studied. 8.1.1. VIII. Among homovalent VIII phosphonates, the nuclearity varies from 4 to 9. Among the mixed valent VIII/VIV compounds, the highest nuclearity found is 13. The reaction of VCl3 with Ph3CPO3H2 afforded a tetranuclear compound, [VIII4(μ4-O)(μ-OH)2(O3PCPh3)4(Py)4] V


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Review

All of the known VIII phosphonates are summarized in Table 10. 8.1.2. VIV and VV. Oxovanadium phosphonates containing VIV and VV and mixed-valent compounds containing VIV/VV have been widely studied. High-nuclearity complexes are more common, particularly in mixed-valent compounds (Table 10).142−167 Among homovalent VIV complexes, the nuclearity varies between 2 and 12. In the case of homovalent VV complexes, the nuclearity varies from 2 to 18. Among the mixed-valent compounds (VIV/VV), the nuclearity varies from 2 to 13. Most of the molecular vanadium phosphonates were prepared by using VCl3, VCl3(THF)3, and [Ph4P][VO2Cl2] as the starting materials. Representative examples are summarized in Figures 42−49. 8.1.3. VIV. Complexes whose nuclearity is 2, 3, or 4 are known in this family (Table 10). Dinuclear complexes [(VO)2(phen)2{t-BuPO2(OH)}2(OH2)2]·2Cl and [(VO)2(bipy)2{t-BuPO2(OH)}2(OH2)2]·2Cl (bipy = 2, 2′bipyridine) have been isolated in reactions of VCl3 and t-BuPO3H2 in the presence of chelating ligands such as 2,2′bipyridine or 1,10-phenanthroline (Scheme 43).143 In the former, two V(O) units are bridged by two [t-BuP(O)2(OH)]− ligands generating an eight-membered V2O4P2 ring. A similar type of a dinuclear compound, but without the chelating ancillary ligands, [V2O2Cl2(C6H5PO3H)2(H2O)2], was obtained in the reaction of (C6H5)4P[VO2Cl2] and PhPO3H2.144 Dinuclear vanadyl phosphonates have also been obtained in the reactions of oxovanadium precursors such as NaVO3 or VOSO4 in reactions with N-(phosphonomethyl) iminodiacetic acid.145 Dicationic trinuclear complexes, [(VO)3(phen)3(Ph3CPO3)2(OH2)3]·[OH]2·CHCl3·2MeOH·1.5H2O and [(VO)3(bipy)3(Ph3CPO3)2(MeOH)3]·[OH]2·4CH3OH·5H2O, are obtained in the reaction of VCl3, Ph3CPO3H2, and a chelating nitrogenous ligand (1,10-phenanthroline or 2,2′-bipyridine). In these complexes, three vanadyl units are arranged in a triangular fashion and are connected to each other with the help of two tripodal phosphonate ligands (Scheme 44).143 The reaction of VCl3 with 3,5-dimethylpyrazole (3,5Me2PzH) and CCl3PO3H2/t-BuPO3H2 in the presence of triethylamine afforded the neutral homovalent tetranuclear derivatives, [(VO)4(3,5-Me2PzH)8(CCl3PO3)4] and [(VO)4(3, 5-Me2PzH)8(t-BuPO3)4] (Scheme 45).146 These complexes possess a distorted cubic structure where alternate corners of the cube are occupied by VIV and P atoms, while the edges of the cube contain the oxygen atoms of the phosphonate ligand. This cubic core resembles the D4R secondary building unit present in zeolites. Each phosphonate ligand assists in holding three VIV centers together. Each of the vanadium centers is in fact a vanadyl unit, which is the typical feature of all of the compounds of the higher valent vanadium phosphonate complexes. The coordination geometry around vanadium is distorted square pyramidal with the vanadyl oxygen atom occupying the apical position.146 A third type of tetranuclear family is exemplified by a trinuclear basket capped by a fourth vanadyl unit, [(t-BuPz)5V4O4(μ-C6H5PO3)4]·4CH3CN·0.6H2O (Figure 42).147 Tetranuclear compounds containing the dinuclear (O)V−O− V(O)(V2O3) motifs are known, some of these such as Mn+[(V2O3)2(RPO3)4F] encapsulating a fluoride ion.148,149 8.1.4. VV. The dinuclear complex [(VO)2(bipy)2(μ2-O)2(tBuPO3)2]·2CH3OH·0.5CH2Cl2 was obtained in the reaction of

Figure 35. μ3-O-Containing tetranuclear titanium phosphonate cage, [Ti4O(OPr-i)8(O3P-xyl)3 (i-PrOH)] (O3P-xyl = bis(trimethylsilyl)(3,5-dimethylphenyl)phosphonate).131 Adapted from ref 131. Copyright 2013 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 36. μ3-O-Containing heptanuclear titanium phosphonate cage, [Ti7(μ3-O)2(μ2-OPr-i)6(OPr-i)6(O3PCH2C6H5)6].131 Adapted from ref 131. Copyright 2013 Wiley-VCH Verlag GmbH & Co. KGaA.

VIII triangles are linked by two phosphonate ligands that bind in a 4.211 mode (Scheme 42).142 Heating the hexanuclear compound under solvothermal conditions afforded a nonanuclear compound, [VIII9(μ3-O)4(O3PBu-t)3(O2CBu-t)13].142 In the molecular structure of the latter, nine of the corners of an icosahedron are occupied by VIII while the other three corners are occupied by the phosphorus atoms of the phosphonate ligands. Only one mixed-valent VIII/VIV phosphonate complex is known. The complex, [VIII12(VIVO)(μ3-OH)4(μ2-OH)8(μ2OEt)4(EtOH)4(PhCO2)4(O3PBu-t)8]Cl2, was obtained in the reaction between [VCl3(THF)3], t-BuPO3H2, benzoic acid, KOEt, and ethanol. The molecular structure of [VIII12(VIVO)(μ3-OH)4(μ2-OH)8(μ2-OEt)4(EtOH)4(PhCO2)4(O3PBu-t)8]Cl2 contains a tetrameric array of (V3O) triangles encapsulating a central VO. The phosphonate ligands bind to the metal ions in 3.111 and 4.211 modes (Figure 41).142 W


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Review

Figure 37. μ3-O-Containing octanuclear titanium phosphonate cage, [Ti8(μ3-O)2(μ2-OPr-i)6(OPr-i)8(O3PCH2CHCH2)6{O2(OPr-i)PCH2CH CH2}2].131 Adapted from ref 131. Copyright 2013 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 39. A pentanuclear titanium phosphonate complex, [Ti5O(OPr-i)11(OAc)(O3PCH2CH2CH2 Br)3] (OAc = acetate).132 Adapted from ref 132. Copyright 2014 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 38. A hexanuclear titanium phosphonate cluster [Ti6O4(OPri)10(OAc)2(O3P(CH2CHCH2)2] (OAc = acetate).132 Adapted from ref 132. Copyright 2014 Wiley-VCH Verlag GmbH & Co. KGaA.

[(n-Bu)4N]4V2W4O19.150 These complexes possess a D4R type core as discussed above, the one difference being that the vanadyl centers are further attached to each other through a μ-O. Also, interestingly, the cubic cage entraps a hydroxide ion in the center of the cage. The tetranuclear complex [Et4P][(V2O3)2(O3PPh)4F], prepared in the reaction of PhPO3H2 and V(OPr-i)3, contains two (O)V−O−V(O) subunits. The vanadium atoms occupy tetrahedral faces, while the corners of the tetrahedron contain the phosphorus atoms. The fluoride ions are present in the center of the cage.149 A pentanuclear complex [n-Bu4N][V5O7(OCH3)2(PhPO3)5]· CH3OH is obtained in the reaction of (n-Bu4N)3V5O14 with PhPO3H2 (Table 10).151,152 The molecular structure of this complex shows an irregular structure possessing a central {(VO)3(μ-O)2}5+ unit comprised of three corner-shared square pyramids. Linked to this trinuclear motif is a distorted octahedral vanadium site through four bridging phosphonate groups. The VO unit of this vanadium site projects inside the cavity of the cage. A fifth square pyramidal vanadium

143

VCl3 with t-BuPO3H2 and bipy in methanol (Scheme 46). This compound is characterized by the presence of two vanadyl units being bridged by two oxide ligands affording a fourmembered V2O2 ring. The two vanadyl units are further linked by a single [t-BuPO3]2− ligand. The latter exhibits a rare 2.11 coordination mode, more reminiscent of the coordination action of a carboxylate ligand (Scheme 46).143 A slight variation of the reaction conditions including modifying the ancillary ligand to 3,5-dimethylpyrazole afforded the homovalent, tetranuclear VV complex, [{(VO)4(Ph3CPO3Me)4(μ-O)4}Cl]·{3,5-Me2PzH2}·3C7H8·H2O·CH3OH (Scheme 47).143 This complex contains a bowl-shaped architecture containing a V4O4 eight-membered ring. Each pair of vanadyl units are bridged by four [Ph3CPO2(OCH3)]− ligands. An interesting aspect of the structure of this complex is that a chloride ion is trapped within the bowl (Figure 43).143 Another family of tetranuclear VV complexes, [[(n-Bu)4N][V 4 O 6 (OH)(PhPO 3 ) 4 ]·xsolv, were obtained in the reactions of phenylphosphonyldichloride (PhPOCl2) with X


Chemical Reviews

Review

Table 9. Molecular Titanium Phosphonates compounds


ref

Ti(OMe)4, [n-Bu4N]2[PhPO3H] (C5Me4Et)TiF3, MeP(O)(OSiMe3)2 t-BuPO3H2, Cp*TiMe3

reactants

[n-Bu4N]2[Ti2(OMe)6(O3PPh)2] [{Ti(C5Me4Et)(μ-O2P(OH)Me)(μ-O2P(O)Me)}2] [(Cp*Ti)3(t-BuPO3)2{t-BuPO2(OH)}(μ-O)2]

129 130 127

Cp*TiMe3/Cp*TiCl3, CH3PO3H2

[(Cp*TiO3PMe)4(μ-O)2]

dinuclear dinuclear/eight-membered ring trinuclear/basket-shaped polyhedron tetranuclear/distorted bicapped cube -do-dodistorted cube tetranuclear -do-do-do-do-do-do-dotetranuclear/sandwich-like

Cp*TiMe3, t-BuPO3H2 [(Cp*TiO3PBu-t)4(μ-O)2] Cp*TiMe3, PhPO3H2 [(Cp*TiO3PPh)4(μ-O)2] Ti(OPr-i)4, t-BuPO3H2 [Ti(OPr-i)2(t-BuPO3)]4 Ti(OPr-i)4, t-BuPO3H2 [Ti4(μ3-O)(OPr-i)5)(μ-OPr-i)3(t-BuPO3)3]·DMSO Ti(OPr-i)4, CH3PO3H2 [Ti4(μ3-O)(OPr-i)5)(μ-OPr-i)3(MePO3)3]·DMSO Ti(OPr-i)4, PhPO3H2 [Ti4(μ3-O)(OPr-i)5)(μ-OPr-i)3(PhPO3)3]·DMSO Ti(OPr-i)4, t-BuPO3H2 [Ti4(μ3-O)(OPr-i)5(μ-OPr-i)3(t-BuPO3)3]·DMSO Ti(OPr-i)4, CH3PO3H2 [Ti4(μ3-O)(OPr-i)5(μ-OPr-i)3(MePO3)3]·DMSO Ti(OPr-i)4, PhPO3H2 [Ti4(μ3-O)(OPr-i)5(μ-OPr-i)3(PhPO3)3]·DMSO PhPO3H2, Ti(OPr-i)4 [Ti4(μ3-O)(OPr-i)5(μ-OPr-i)3(PhPO3)3]·DMSO Ti(OEt)4, PhPO3H2, NH4(OAc), NH4Br, MnBr2·4H2O [Ti4O(OEt)12(PhPO3)] Ti(OPr-i)4, CH2CH−CH2−PO3H2, RPO(OSiMe3)2 [Ti4O(OPr-i)8(CH2CH−CH2PO3)3(DMSO)] (R = CH2CH−CH2−), i-PrOH Ti(OPr-i)4, RPO(OSiMe3)2, R = 3,5-dimethylphenyl (xylyl), i-PrOH [Ti4O(OPr-i)8(O3P−xyl)3(i-PrOH)] Ti(OPr-i)4, RPO(OSiMe3)2, R = 2-naphthylmethyl, i-PrOH [Ti4(μ2-OPr-i)(OPr-i)7(O3PMeNp)4(i-PrOH)2·2iPrOH] [Ti5O(OPr-i)11(OAc)(O3PCH2CH2CH2−Br)3] Ti(OPr-i)4, CH3CO2H, i-PrOH, RPO(OSiMe3)2 (OAc = acetate) (R = BrCH2CH2CH2−) Ti(OPr-i)4, CH3CO2H, i-PrOH, RPO(OSiMe3)2 (R = xylyl) [Ti5O3(OPr-i)6(OAc)4(O3Pxylyl)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, EtPO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PEt)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, NpCH2PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PCH2Np)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, CH2CH−PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PCHCH2)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, CH2CH−CH2−PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2 (O3PCH2CHCH2)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, ClCH2CH2CH2PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PCH2CH2CH2−Cl)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, C6H5CH2−PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PCH2Ph)2] Ti(OPr-i)4, CH3CO2H, i-PrOH, BrCH2CH2CH2−PO(OSiMe3)2 [Ti6O4(OPr-i)10(OAc)2(O3PCH2CH2CH2−Br)2] Ti(OPr-i)4, i-PrOH, ClCH2CH2CH2−PO(OSiMe3)2 [Ti7(μ3-O)2(μ2-OPr-i)6(OPr-i)6 (O3PCH2CH2CH2Cl)6] [Ti7(μ3-O)2(μ2-OPr-i)6(OPr-i)6(O3PCH2C6H5)6] Ti(OPr-i)4, i-PrOH, C6H5CH2PO(OSiMe3)2 Ti(OPr-i)4, i-PrOH, CHCH−CH2−PO(OSiMe3)2 [Ti8O2(OPr-i)12{O3PO2PCH2CHCH2}6 {O2PCH2CHCH2)(OPr-i)}2] Ti(OPr-i)4, i-PrOH, CH2CHPO(OSiMe3)2 [Ti8(μ3-O)2(μ2-OPr-i)6(OPr-i)8(O3PCHCH2)6 {O2P(OPr-i)CHCH2}2] Ti(OEt)4, PhPO3H2, NH4(OAc), NH4Br, MnBr2·4H2O [Ti25O26(OEt)36(PhPO3)6] Ti(OEt)4, PhPO3H2, NH4(OAc), NH4Br, MnBr2·4H2O [Ti26O26(OEt)39(PhPO3)6]·Br

127 127 127 135 133 133 133 135 135 135 128 136 131

-do-do-

131 131

pentanuclear

132

-dohexanuclear -do-do-do-do-do-doheptanuclear

132 132 132 132 132 132 132 132 131

-dooctanuclear

131 131

octa-nuclear

131

pentaicosa nuclear hexaicosa nuclear

136 136

Scheme 38. Preparation of Trinuclear O-Capped Zirconium Phosphinate/Phosphate Clusters140

Scheme 39. Synthesis of Zirconium Phosphinate/Phosphates Containing a Dinuclear Zr2O2 Core140

site is linked to the above-described tetranuclear motif through phosphonate bridges. Another pentanuclear anion [Ph4P][V5O7(OCH3)2(PhPO3)5] was obtained in the reaction of [Ph4P][VO2Cl2] and PhPO3H2.153

8.1.5. VIV/VV. Mixed-valent VIV/VV phosphonate complexes have been most widely studied, and most of these contain the VO motif. The nuclearity of these complexes varies from 4 to 13 (Table 10).142−167 Y


Chemical Reviews

Review

Scheme 42. Synthesis of the Homovalent VIII Phosphonate Cage, [VIII6(μ3-O)2(O2CBu-t)8(HO2CBu-t)2(HO3PBu-t)2(O3PBu-t)2], and Its Conversion to [VIII9(μ3-O)4(O3PBu-t)3(O2CBu-t)13]142

Scheme 40. An Alkoxide-Bridged Dinuclear Zirconium Phosphinate Complex, [(OPr-i)3Zr(μ-OPr-i)2 (μ-OPOPh2)Zr(OPr-i)2Ph2P(O)(OH)]141

Scheme 41. Synthesis of a Tetranuclear VIII Phosphonate Cage, [VIII4(μ4-O)(μ-OH)2(O3PCPh3)4(py)4]142

Figure 40. A pentanuclear vanadium phosphonate cage, [V III 5 (μ 3 -OH)(O 3 PBu-t) 6 Cl2 (Py) 6 ].142 Adapted from ref 142. Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

The tetranuclear complex, [Ph4P][(VO)4{PhP(O)2OP(O)2Ph}4Cl], is built by the coordination action of the four pyrophosphonate ligands [PhP(O)2OP(O)2Ph]2−, which are formed in situ.153 Such metal-mediated condensation of phosphonic acids is known.154 This tetranuclear complex does not possess V−O−V linkages and contains discrete vanadiumcentered square pyramids. Several fluoride-templated tetranuclear complexes [(V2O3)2(RPO3)4F] [R = Me, Ph, i-Pr] were prepared in the reactions of [VO2Cl2]− salts with various phosphonic acids in the presence of KF (Table 10).148 In these

Figure 41. Core of a mixed-valent VIII/VIV tridecanuclear vanadium phosphonate, [V I I I 1 2 (V I V O)(μ 3 -OH) 4 (μ 2 -OH) 8 (μ 2 -OEt) 4 (EtOH)4(PhCO2)4(O3PBu-t)8]Cl2.142 Adapted from ref 142. Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA.

compounds, four VO5 square pyramids are held together by four phosphonate tetrahedra. Within the tetranuclear vanadium Z


(Ph4P)VO2CI2, t-BuPO3H2 (Ph4P)VO2CI2, PhPO3H2 (Ph4P)VO2CI2, MePO3H2 VCl3, t-BuPO3H2, NEt3, phen VCl3, t-BuPO3H2, NEt3, bipy VCl3, t-BuPO3H2, NEt3, bipy (C6H5)4P[VO2C12], PhPO3H2 VCl3, Ph3CPO3H2, NEt3, phen VCl3, Ph3CPO3H2, NEt3, bipy VCl3, [VCl3(THF)3], NEt3, Ph3CPO3H2, pyridine PhPO3H2, [Ph4P][VO2CI2] VCl3, 3,5-dimethylpyrazole (3,5-Me2PzH), CCl3PO3H2, NEt3 VCl3, 3,5-Me2PzH, t-BuPO3H2, NEt3 tert-butylpyrazole (t-BupzH), C6H5PO3H2, (t-Bupz)2VOCl2 t-BupzH, (t-Bupz)2VOCl2, C6H5PO3Na2·xH2O [(n-Bu)4N]4V2W4O19, PhPOCl2 Mn[VO2Cl2]n (M = Ph4P, (Et2N)3PCH2Ph, Ph3P (CH2)2PPh3), KF, PhPO3H2 Mn[VO2Cl2]n (M = Ph4P), KF, CH3PO3H2 Mn[VO2Cl2]n (M = Ph4P), KF, i-PrPO3H2 VO(OPr-i)3, PhPO3H2, [Et4P][AlF4] VO(OPr-i)3, MePO3H2, [Et4P][AlF4] [Et4P][(V2O3)2(O3PMe)4F, 4-tert-butylpyridine VCl3, Ph3CPO3H2, NEt3, 3,5-Me2PzH N-(phosphonomethyl)iminodiacetic acid (H4pmida), KVO3, ZnO, imidazole (Im), adipic acid H4pmida, NaOH, VOSO4·5H2O, pyrazine, ZnSO4·2H2O, Im [VCl3(THF)3], pyridine, NEt3, t-BuPO3H2 (Bu4N)3V5O14, PhPO3H2, (NH4)H2PO4 PhPO3H2, [Ph4P][VO2CI2], (NH4)H2PO4 PhPO3H2, [Ph4P][VO2CI2] [C4H9)4N]3[V5O14], PhPO3H2 [VCl3(THF)3], pyridine, NEt3, t-BuPO3H2 t-BuPO3H2, [Ph4P][VO2CI2] VCl3, t-BuPO3H2, t-BuCO2H, Et3N, KOEt [VCl3(THF)3], Et3N, KOEt, t-BuPO3H2, t-BuCO2H [VCl3(THF)3], t-BuPO3H2, PhCO2H, Et3N, KOEt [VCl3(THF)3], Et3N, KOEt, t-BuPO3H2, t-BuCO2H [V2OCl4(THF)6], Et3N, t-BuPO3H2, pyridine (MePPh3)[VO2Cl2], t-BuPO3H2, template (T = Cl−, HCl, OH−)

reactants

Table 10. Molecular Vanadium Phosphonates ref

147 150 148 148 148 149 149 149 143 163

-do-do-do-do-do-do-do-dotetranuclear/bowl-shaped heterometallic; tetranuclear -dopentanuclear -do-do-do-dohexanuclear -do-do-do-do-do-do-do-

[(t-Bupz)5V4O4(μ-C6H5PO3)4·4CH3CN·0.6H2O [[(n-Bu)4N][V4O6(OH)(PhPO3)4]·Me2CO; [(n-Bu)4N][V4O6(OH)(PhPO3)4]·0.5MeCN [Ph4P][(V2O3)2(PhPO3)4⊂F]·CH3CN; [Ph3P(CH2)2PPh3][(V2O3)2(PhPO3)4F]2; [(Et2N)3PCH2Ph][(V2O3)2(PhPO3)4F] [Ph4P][(V2O3)2(MePO3)4⊂F]·2CH3CN [Ph4P][(V2O3)2(i-PrPO3)4⊂F] [Et4P][(V2O3)2(O3PPh)4F] [Et4P][(V2O3)2(O3PMe)4F] [Et4P]1.5[(4-tert-butylpyridine)2H][(V2O3)2(MePO3)4F] [{(VO)4(Ph3CPO3Me)4(μ-O)4}Cl]·{3,5-Me2PzH2}·3C7H8·H2O·CH3OH [Zn2V2(C5H6NO7P)2O2(H2O)10]·2H2O [Zn2V2O2(pmida)2(H2O)10]·H2O; [Zn2V2O2(pmida)2(H2O)12]·2H2O

AA

[VIII5(μ3-OH)(O3PBu-t)6Cl2(py)6] (Bu4N)[V5O7(OCH3)2(PhPO3)5]·CH3OH (Ph4P)2[V5O9(PhPO3)3(PhPO3H)2] [Ph4P][V5O7(OCH3)2(PhPO3)5] [C4H9)4N][V5O7(OMe)2(PhPO3)5]·CH3OH [VIII6(μ3-O)2(O2CBu-t)8(HO2CBu-t)2(HO3PBu-t)2(O3PBu-t)2] [(VO)6(t-BuPO3)8Cl] [VIII6(O)2(O2CBu-t)8(HO2CBu-t)2(HO3PBu-t)2(O3PBu-t)2] [VIII6(μ3-O)2(t-BuPO3)2(t-BuPO3H)2(t-BuCO2)8(THF)2] [VIII6(O)2(t-BuPO3)2(t-BuPO3H)2(PhCO2)8(EtOH)2] (Et3NH)2[VIII6(O)2(t-BuPO3)2(t-BuPO3H)2(t-BuCO2)8(t-BuPO3H)2] [VIII6(μ3-O)2(t-BuPO3)4(μ2-Cl)4(Cl)2(py)8] [(VO)6(t-BuPO3)8⊂Cl−]; [(VO)6(t-BuPO3)8⊂T] (T = HCl, OH)

142 152 152 153 151 142 153 158 158 158 158 165 155

164

146 147

-do-do-

162 162 162 143 143 143 144 143 143 142 153 146

[(VO)4(3,5-Me2PzH)4(t-BuPO3)4] [(t-Bupz)4V4O4(μ-C6H5PO3)4]·2H2O

nuclearity/structure dinuclear -do-do-do-do-do-dotrinuclear trinuclear/propellane-type bicyclic structure tetranuclear -dotetranuclear/D4R core

compounds (Ph4P)2[(VO)2Cl4(t-BuPO3H)2 [(VO)2C12(H2O)2(PhPO3H)2] [(VO)2C12(H2O)2(MePO3H)2] [(VO)2(phen)2{t-BuPO2(OH)}2(OH2)2]·2Cl [(VO)2(bipy)2{t-BuPO2(OH)}2(OH2)2]·2Cl [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]·2CH3OH·0.5CH2Cl2 [V2O2C12(PhPO3H)2(H2O)] [(VO)3(phen)3(Ph3CPO3)2(OH2)3]·CHCl3·2(OH)·2MeOH·1.5H2O [(VO)3(bipy)3(Ph3CPO3)2(CH3OH)3]·2(OH)·4CH3OH·5H2O [VIII4(μ4-O)(μ-OH)2(O3PCPh3)4(py)4] [(VO)4{(PhP(O)2OP(O)2Ph)}4C1] [(VO)4(3,5-Me2PzH)8(CCl3PO3)4]

Chemical Reviews Review


AB

(Et4N)VO3, t-BuPO3H2, AgCCBu-t, AgBF4, (BzEt3N)Cl, aqueous H2O2, 2-chloropyridine

(MePPh3)[VO2Cl2], PhPO3H2, template (T = Cl−, MeCN) H4pmida, NaVO3, NaHCO3, NaOH (MePPh3)[VO2Cl2], t-BuPO3H2, template (T = NO3−) (MePPh3)[VO2Cl2], PhPO3H2, T = Cl− (Ph4P)VO2Cl2, PhPO3H2 [VCl3(THF)3], KOEt, Et3N, NpCH2PO3H2 (Np = naphthyl), pyridine [VCl3(THF)3], Et3N, PhCH2PO3H2 [VCl3(THF)3], pyridine, NEt3, t-BuPO3H2 H4pmida, NaVO3, NaHCO3, NaOH (n-Bu4N){V5O7(OMe)2 (PhPO3}5, HCl (aq) VCl3, Ph2CHPO3H2, NEt3 PhPO3H2, VOSO4·3H2O, [n-Pr)4NOH], hydrothermal [VCl3(THF)3], pyridine, NEt3, t-BuPO3H2, KOEt [VCl3(THF)3], t-BuPO3H2, PhCO2H, Et3N, KOEt NH4VO3, PhPO3H2, Me2NHCl [t-BuNH3]4[V4O12], CH3PO3H2, KOH V2O3, V2O5, CH3PO3H2, Me4NOH PhPO3H2, [Ph4P][VO2CI2], NEt3 (Et4N)VO3, t-BuPO3H2, AgCCBu-t, AgBF4, (BzEt3N)Cl, aqueous H2O2

reactants

Table 10. continued

heptanuclear -dooctanuclear -dononanuclear heterometallic; decanuclear dodecanuclear/bowl-shaped -do-dotridecanuclear -dotetradecanuclear -dohexadecanuclear octadecanuclear octaicosanuclear

(Ph4P)2[(V4O7)(V3O5)(PhPO3)6⊂Cl−] (Ph4P)2[ClV7O12(O3PC6H5)6] [VIII8(μ4-O)2(μ2-OH)2(NpCH2PO3)8(EtOH)8·2Cl [VIII8(μ3-O)2(PhCH2PO3)6(PhCH2PO3H)8(py)8 [VIII9(μ3-O)4(O3PBu-t)3(O2CBu-t)13] Na8[V2O2{(O)2P(O)CH2N(CH2CO2)2}2]2·16H2O (n-Bu4N)2[{V8O16}{V4O4(H2O)12(PhPO3)8Cl2]·2Et2O·2MeOH·4H2O (HNEt3)2[(V12O20)(H2O)12(Ph2CHPO3)8]·(H2O)7·(CH3CN)4·2Cl [N(C3H7)4]4[H12(VO2)12(PhPO3)8]·1.48H2O [VIII12(VIVO)(μ3-OH)4(μ2-OH)8(μ2-OEt)4(EtOH)4(PhCO2)4(O3PBu-t)8]·2Cl [VIII12(VIVO)(μ3-OH)4(μ2-OH)8(μ2-OEt)4(EtOH)4(PhCO2)4(O3PBu-t)8]·2Cl [NH4]2[V14O22(OH)4(H2O)2(C6H5PO3)8Cl2]·5H2O·4Me2NCHO [H6KV12O27(VO4)(PO3CH3)3] [N(CH3)4]8[H6(VO2)16(CH3PO3)16]·11H2O [Ph4P]4[V18O25(H2O)2(PhPO3)20Cl4]·6CH3CN·2CH3OH {2Cl@Ag21(CCBu-t)9[(t-BuPO3)3V3O6(OH)]2[(t-BuPO3)VO2(OH)] (MeOH)2(H2O)2}·2MeOH·2H2O; {2C2@Ag21(CCBu-t)9[(t-BuPO3)3V3O6(OH)]2[(tBuPO3)VO2(OH)](MeOH)2(H2O)2}·2MeOH·2H2O [(Et)4N]3[{(O2)V2O6}2@Ag36(CCBu-t)12{(t-BuPO3)4V4O8}2(t-BuPO3)2(NO3)7(2-ClPy) (DMF)]; [(Et)4N]2[{(O2)V2O6}2Cl@Ag36(CCBu-t)11{(t-BuPO3)4V4O8}2{(t-BuPO3)2 (VO2)}(t-BuPO3)2(t-BuPO3H)(DMF)(NO3)2(Et2O)(H2O)3]·2DMF·2Et2O·4H2O

octatetracontanuclear

heterometallic hexanuclear heptanuclear

Na4[V2O2{(O)2P(O)CH2N(CH2CO2)2}2]·10H2O [(V3O5)(VO)4(t-BuPO3)8⊂NO3−]

nuclearity/structure -do-

compounds [(VO)6(PhPO3)8⊂Br−]⊂solv; (Ph3PMe)2[(VO)6(PhPO3)8⊂Cl−]3

ref

167

142 158 160 159 161 153 167

165 142 145 156 157 166

155 162 165

145 155

155



Chemical Reviews

Review

Figure 42. A tetranuclear vanadium phosphonate, [(t-BuPz)5V4O4(μC6H5PO3)4]·4CH3CN·0.6H2O.147 Adapted from ref 147. Copyright 1996 American Chemical Society.

Figure 44. Fluoride-templated tetranuclear vanadium phosphonates (a) [Ph 4 P][(V 2 O 3 ) 2 (MePO 3 ) 4 ⊂F]·2CH3 CN and (b) [Ph 4 P][(V2O3)2(PhPO3)4⊂F]·CH3CN.148 Adapted from ref 148. Copyright 2008 American Chemical Society.

Figure 43. (a) Molecular structure of a V4 phosphonate cage. (b) Bowl-shaped core of [{(VO) 4 (Ph 3 CPO 3 Me) 4 (μ-O) 4 }Cl]·{3,5Me2PzH2}·3C7H8·H2O·CH3OH.143 Adapted from ref 143. Copyright 2014 The Royal Society of Chemistry.

Figure 45. Hexanuclear vanadium phosphonate, [(VVO)5(VIVO)(tBuPO3)8Cl], showing an equatorial plane of four vanadium centers; one vanadium is on the top and the other is on the bottom of this plane.153 Adapted from ref 153. Copyright 1994 Wiley-VCH Verlag GmbH & Co. KGaA.

motif are present two dinuclear V2O3 subunits possessing a V−O−V linkage (Figure 44).148 Multinuclear NMR (51V, 19F, and 31P) studies involving a study of the change of chemical

shifts demonstrated the templating role of the fluoride ion in the formation of the cage structure. A similar tetranuclear compound, [Et4P]1.5[(C9H13N)2H]0.5[(V2O3)2(O3PPh)4F], AC


Chemical Reviews

Review

Figure 48. A hexanuclear CrIII/CoII carboxylate cluster [CoII4CrIII2(μ4O)2(O2CBu-t)10(Me2CO)2].170 Adapted from ref 170. Copyright 2010 The Royal Society of Chemistry.

Figure 46. A bowl-shaped dodecanuclear vanadium phosphonate cage, [HNEt 3 ] 2 [(V 8 O 16 ){V 4 O 4 (H 2 O) 12 }(Ph 2 CHPO 3 ) 8 Cl 2 ]·(H 2 O) 7 · (CH3CN)4.157 Adapted from ref 157. Copyright 2008 American Chemical Society.

(trimethylsilyl)phosphate, ((Me3SiO)3PO), and VOCl3.149 The structure of this compound is cube-shaped, with the faces of the cube being occupied by a vanadyl unit; the phosphorus atoms occupy the corners of the cube. The center of the cube traps a chloride ion. Each of the vanadium centers possesses a square-pyramidal geometry. Also, V−O−V linkages are absent in this complex.149 A heptanuclear complex, [(V3O5)(VO)4(t-BuPO3)8⊂NO3], containing a trapped nitrate anion was obtained in a solvothermal synthesis protocol involving (MePPh3)[VO2Cl2] and t-BuPO3H2 in the presence of templating anions.155 The overall spherical cage structure of this compound is supported by the bridging coordination of the organophosphonate units. A d odecanuclear complex, [n-B u 4 N] 2 [(V 8 O 1 6 ){V4O4(H2O)12}(PhPO3)8Cl2]·2Et2O·2MeOH·4H2O, was obtained in the reaction of the pentanuclear oxovanadium phosphonate, (n-Bu 4 N)[V 5 O 7 (OMe) 2 (PhPO 3 ) 5 ], with HCl.156 The molecular structure of this compound reveals that two apical (VV4O8)4+ motifs are present, each of which contains four V−O−V linkages. Adjacent vanadyl units are connected to each other by the bridging coordination of four phosphonate groups. The two apical tetranuclear motifs are connected to a central rim of four [VIV(O)(H2O)3]2+ units. Two chloride anions are trapped in the upper and lower portions of the cage, which have a bowl-shaped topology. Another dodecanuclear complex, [HNEt3]2[(V8O16){V4O4(H2O)12}(Ph2CHPO3)8Cl2]·(H2O)7·(CH3CN)4, possessing structural features identical to those described above, was prepared in a direct reaction of VCl3 and Ph2CHPO3H2 (Figure 46).157 Tri- and tetradecanuclear mixed-valent vanadium phosphonates are known.158−160 A heterometallic complex [H6KV12O27(VO4)(O3PCH3)3]5−, prepared in a photochemical reaction involving [t-BuNH3]4[V4O12], CH3PO3H2, and C6H5PO3H2 in the presence of KOH, in an aqueous medium, is a potassium capped cage containing nine VIVO6 octahdera, four VVO4 tetrahedra, and three organophosphonate moieties.159 The reaction of ammonium metavanadate, phenylphosphonic acid, and hydrazine hydrate along with dimethylammonium chloride afforded the tetradecanuclear compound [NH4]2[V14O22(OH)4(H2O)2(C6H5PO3)8Cl2]·5H2O·4Me2NCHO.160 Two

Figure 47. A mixed-metal Cr III /Mn III phosphonate cage [Mn3CrO2(O2CCH3)4(O3PC5H4N)2 (bipy)2].169 Adapted from ref 169. Copyright 2008 American Chemical Society.

containing a fluoride in the center of the tetrahedral cage is also known.149 The mixed-valent complex (Ph 4 P) 2 [V 5 O 9 (PhPO 3 ) 3 (PhPO3H)2] was obtained in the hydrothermal reaction of (Ph4P)[VO2Cl2], PhPO3H2, and (NH4)H2PO4.152 The molecular structure of the mixed-valent complex bears considerable similarities to the homovalent pentanuclear VV complex described above,151,152 the difference being that the fourth and fifth vanadium sites possess square-pyramidal and tetrahedral geometries, respectively. A solvothermal reaction of t-BuPO3H2 and [Ph4P][VO2Cl2] afforded the hexanuclear complex, [(VVO)5(VIVO)(t-BuPO3)8Cl] (Scheme 48),153 which possesses a spherical shell comprised of vanadium, phosphorus, and oxygen atoms. The spherical shape of this complex is constructed by the interlinking of six {VO}5 square-pyramids with eight [t-BuPO3]2− ligands. The other feature of the structure is the absence of V−O−V linkages. Interestingly, a chloride ion is trapped within the cavity of the sphere (Figure 45).153 The hexanuclear compound, [(VO)6(O3POSiMe3)8Cl], containing five VV and one VIV has been prepared in the reaction of AD


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Figure 49. A heterometallic dodecanuclear CrIII/CoII phosphonate cage, [Co8Cr4(μ3-OMe)2(O3PBu-t)4(O2CBu-t)8(μ-OMe)10(HOMe)6]· (MeOH)1.6.170 Adapted from ref 170. Copyright 2010 The Royal Society of Chemistry.

Scheme 43. Synthesis of Dinuclear Vanadium Phosphonates, [(VO)2(phen)2{t-BuPO2(OH)}2(OH2)2]·2Cl and [(VO)2(bipy)2{t-BuPO2(OH)}2(OH2)2]·2Cl143

Scheme 44. Synthesis of Trinuclear Vanadium Phosphonates, [(VO)3(phen)3(Ph3CPO3)2(OH2)3]·[OH]2·CHCl3·2MeOH· 1.5H2O and [(VO)3(bipy)3(Ph3CPO3)2(MeOH)3]·[OH]2·4CH3OH·5H2O143

{V5O9}3+ units lie on each side of two dinuclear vanadium motifs; the connection between these is established by the [C6H5PO3]2− ligands. Chloride and ammonium ions are trapped within the cavity of the cage. A hexadecanuclear complex [N(CH 3 ) 4 ] 8 [H 6 (VO 2 ) 16 (CH3PO3)8]·11H2O suggested to contain 16 VV and two VIV was obtained in a hydrothermal synthesis involving CH3PO3H2, V2O3, V2O5, and Me4NOH. Four (VO2)4 motifs are connected to each other through the mediation of the phosphonate groups.161 Heating the pentanuclear VV complex, [Ph4P][V5O7(OCH3)2(PhPO3)5], in acetonitrile afforded an octadecanuclear complex, [Ph4P]4[V18O25(H2O)2(PhPO3)20Cl4]·xsolv.153 In this giant anion, four {V4O}6(PhPO3)5}2− motifs are arranged in a cyclic manner and are linked to a central {V2O(H2O)2}8+ unit. This arrangement

results in the formation of four cavities, each of which traps a chloride anion.153 All of the molecular vanadium phosponatess and heterometallic silvervanadate phosphonate clusters are listed in Table 10.142−167 Heterometallic silver−vanadate phosphonate complexes are discussed in the section on silver. 8.2. Niobium

Only one dinuclear NbV phosphonate is known. A few NbV polyoxometal phosphonates are also known.137 The reaction of [n-Bu4N][PhPO3H] with Nb(OMe)5 afforded a dinuclear NbV phosphonate complex [n-Bu4N]2[Nb2(μ-O)(OMe)6(O3PPh)2].129 The two NbV ions in this complex are held together by two [PhPO3]2− and one μ-O ligands. In addition, AE


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Scheme 45. Synthesis of a Tetranuclear Vanadium Phosphonate, [(VO)4(3,5-Me2PzH)8(CCl3PO3)4] and [(VO)4(3,5-Me2PzH)8(t-BuPO3)4], Possessing a D4R Core146

Scheme 49. Synthesis of a Dinuclear Niobum Phosphonate, [n-Bu4N]2[Nb2(μ-O)(OMe)6(O3PPh)2]129

each of the niobium centers is also coordinated by three methoxide ligands (Scheme 49).129 8.3. Tantalum

A dinuclear tantalum phosphonate was reported by Roesky and his co-workers. This complex was prepared in a reaction between (η5-C5Me5)TaMe4 and t-BuPO3H2 (Scheme 50).168

Scheme 46. Synthesis of a Dinuclear VV Phosphonate, [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]·2CH3OH·0.5CH2Cl2143

Scheme 50. Synthesis of the Dinuclear Tantalum Phosphonate, [{(η5-C5Me5)Ta}{t-BuPO(OH)2}]2· (t-BuPO3)2·(μ-O)2168

Scheme 47. Synthesis of a Tetranuclear Bowl-Shaped Vanadium Phosphonate, [{(VO)4(Ph3CPO3Me)4(μO)4}Cl]·{3,5-Me2PzH2}·3C7H8·H2O·CH3OH143a

The structure of this compound contains two μ-O bridging ligands as well as two bridging [t-BuPO3]2− ligands. In this reaction, only the alkyl groups on tantalum are involved in Ta−C bond scission leading to the formation of the product.

9. GROUP 6 PHOSPHONATES 9.1. Chromium a

Homometallic molecular CrIII phosphonates are not known. Examples of heterometallic CrIII/MnIII, CrIII/CoII, and CrIII/LnIII complexes are known.169−171 These are discussed below. The reaction of Mn(O2CCH3)2·xH2O/Mn(O2CPh)2·xH2O with phosphonic acids (2-pyridylphosphonic acid; (2-pyridylN-oxide)phosphonic acid; cyclohexylphosphonic acid) in the presence of the oxidizing agent (NBu4)2Cr2O7 and chelating nitrogen ligands afforded the tetranuclear heterometallic complexes, [Mn 3 CrO 2 (O 2 CCH 3 ) 4 (O 3 PC 5 H 4 N) 2 (bipy) 2 ], [Mn 3 CrO 2 (O 2 CPh) 4 (O 3 PC 5 H 4 N) 2 (phen) 2 ], [Mn 3 CrO 2 (O 2 CPh) 4 (O 3 PC 5 H 4 NO) 2 (bipy) 2 ], [Mn 3 CrO 2 (O 2 CPh) 4 (O 3 PC 6 H 11 ) 2 (bipy) 2 ], [Mn 3 CrO 2 (O 2 CPh) 4 (O 3 PC 6 H 11 ) 2 (phen)2], and [Mn3CrO2(O2CCH3)4(O3PC6H11)2(bipy)2].169 As can be seen, the composition of the complexes is unaffected by the change of the phosphonic acid or the chelating ligand. All of the complexes contain a [M4O2]8+ core; the manganese and the chromium ions are in the +3 oxidation state. The core structure of these complexes is similar to the well-known

An encapsulated chloride ion is not shown.

Scheme 48. Synthesis of a V6 Phosphonate Cage, [(VVO)5(VIVO)(t-BuPO3)8Cl]153

AF


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Figure 50. Heterometallic CrIII/LaIII phosphonate core of [CrIII6LaIII2(μ3-O)2(H2O)2(O3PBu-t)4(O2CBu-t)12(HOBu-i)2(i-PrNH2)2].171 Adapted from ref 171. Copyright 2014 The Royal Society of Chemistry.

Table 11. Molecular Cr/Mn, Cr/Co, and Cr/Ln Phosphonates reactants

compounds


ref 169

[Mn3CrO2(O2CPh)4(O3PC6H11)2(phen)2] [Mn3CrO2(O2CCH3)4(O3PC6H11)2(bipy)2] [Mn3CrO2(O2CCH3)4(O3PC5H4N)2(bipy)2]

tetranuclear/ butterfly shaped -do-do-do-

169 169 169

[Mn3CrO2(O2CCH3)4(O3PC5H4N)2(phen)2]

-do-

169

[Mn3CrO2(O2CPh)4(O3PC5H4NO)2(phen)2]

-do-

169

HO2CPh, Mn(O2CPh)2·2H2O, [(n-Bu)4N]2Cr2O7, bipy, C6H11PO3H2, NEt3

[Mn3CrO2(O2CPh)4(O3PC6H11)2(bipy)2]

HO2CPh, Mn(O2CPh)2·2H2O, [(n-Bu)4N]2Cr2O7, phen, C6H11PO3H2, NEt3 Mn(OAc)2·4H2O, MeCO2H, [(n-Bu)4N]2Cr2O7, bipy, C6H11PO3H2, NEt3 Mn(OAc)2·4H2O, MeCO2H, [(n-Bu)4N]2Cr2O7, bipy, 2-pyridylphosphonic acid (C5H4NPO3H2), NEt3 Mn(OAc)2·4H2O, MeCO2H, [(n-Bu)4N]2Cr2O7, phen, 2-pyridylphosphonic acid (C5H4NPO3H2), NEt3 HO2CPh, Mn(O2CPh)2·2H2O, [(n-Bu)4N]2Cr2O7, phen, (2-pyridyl-N-oxide) phosphonic acid [Cr3(μ3-O)(O2CBu-t)6(H2O)3]·(O2CBu-t), [Co2(μ-OH2)(O2CBu-t)4 (HO2CBu-t)4], [Co4Cr2(μ4-O)2(O2CBu-t)10(Me2CO)2], t-BuPO3H2 [CrIII3(μ3-O)(O2CBu-t)6(H2O)3][O2CBu-t]·3H2O, t-BuPO3H2, i-PrNH2, HOBu-i, LnIII(NO3)3·nH2O [CrIII3(μ3-O)(O2CBu-t)6(H2O)3][O2CBu-t]·3H2O, Gd(NO3)3·6H2O, t-BuPO3H2, HOBu-i [Co4Cr2(μ4-O)2(O2CBu-t)10(Me2CO)2], [Cr3(μ3-O)(O2CBu-t)6(H2O)3]· (O2CBu-t), [Co2(μ-OH2)(O2CBu-t)4(HO2CBu-t)4], t-BuPO3H2

[Co4Cr4(μ3-OH)4(O3PBu-t)2(O2CBu-t)6(μoctanuclear OEt)4(OEt)2(HO2CBu-t)4]·(EtOH)0.8 [CrIII6LnIII2(μ3-O)2(H2O)2(O3PBu-t)4(O2CBu-dot)12(HOBu-i)2(i-PrNH2)2], LnIII = La, Tb, Dy, Ho [CrIII6GdIII2(μ3-O)2(H2O)2(O3PBu-t)4(O2CBu-dot)12(HOBu-i)4] [Co8Cr4(μ3-OMe)2(O3PBu-t)4(O2CBu-t)8(μdodecanuclear OMe)10(HOMe)6]·(MeOH)1.6

170 171 171 170

Table 12. Molecular Molybdenum Phosphonates reactants (η5-C5Me5)MoCl4, PhPO3H2 [MoV2O4(H2O)6]2+, H2O3PC(C3H6NH2)(OH) PO3H2, Et2NH H2O3PCH2COOH, MoO4·2H2O, KCl, RbCl, H2O3PC2H4COOH [MoV2O4(H2O)6]2+ or [MoVIO4]2−, H2O3PC(C3H6NH2)(OH)PO3H2 Na2MoO4·2H2O, N2H4·H2O, H4P2CH2O6 ethylenediamine (enH2), Na2MoO4·2H2O piperazine (ppzH2), Na2MoO4·2H2O [MoV2O4(H2O)6]2+ or [MoVIO4]2−, H2O3PC(C3H6NH2)(OH)PO3H2 Na2MoO4·2H2O, N2H4·H2O, H4P2CH2O6 Na2MoO4·2H2O, MoO3, NH4Cl, H2O3PC6H5, KCl, H2O, hydrothermal [MoV2O4(H2O)6]2+ or [MoVIO4]2−, H2O3PC(C3H6NH2)(OH)PO3H2 Na2MoO4·2H2O, N2H4·H2O, H4P2CH2O6 Na2MoO4·2H2O, ATMP, HClO4

compounds


ref

[{(η5-C5Me5)Mo}{PhPO(OH)2}]2(PhPO3)2(μ-O)2 [(C2H5)2NH2]4[MoV4O8(O3PC(C3H6NH3)(O)PO3)2]·6H2O; [(C2H5)2NH2]6[MoV4O8(O3PC(C10H14NO)(O)PO3)2]·18H2O Rb4KNa[(O2CCH2PO3)2Mo5O15]·H2O; Rb4KNa[(O2CC2H4PO3)2Mo5O15]

dinuclear tetranuclear

168 172

pentanuclear

173

(NH4)6[(MoV2O4)(MoVI2O6)2(O3PC(C3H6NH3)(O)PO3)2]·12H2O

hexanuclear

172

Na8[(Mo2O4)3(O3PCH2PO3)3(MoO4)]·18H2O (enH2)4[Mo7O16(O3PCH2PO3)3]·7H2O (ppzH2)4[Mo7O16(O3PCH2PO3)3]·8H2O Li8[{MoV2O4(H2O)}4(O3PC(C3H6NH3)OPO3)4]·45H2O

heptanuclear -do-dooctanuclear

174 175 175 172

Na11[Na(H2O)2{(Mo2O4)4(O3PCH2PO3)4(CO3)2}]·70H2O (NH4)5Na4[{Mo6O15(HO3PC6H5)(O3PC6H5)}2]·6H2O

-dododecanuclear

174 176

Na2Rb6[(MoVI3O8)4(O3PC(C3H6NH3)(O)PO3)4]·26H2O

-do-

172

Na24[Na4(H2O)6{(Mo2O4)10(O3PCH2−PO3)10(CH3CO3)8(H2O)4}]·103H2O; Na28[Na2{(Mo2O4)10(O3PCH2PO3)10 (HCO2)10}]·110H2O Na5[H7{N(CH2PO3)3}Mo6O16(OH)(H2O)4]4·18H2O

icosanuclear

174

tetraicosanuclear

177

oxo-bridged Mn4 compounds and contains a planar array of the metal ions linked to each other by the μ3-oxide ligand. In each

case, the terminal metal ions bear the chelating nitrogen ligands. Both the phosphonate and the carboxylate ligands AG


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Scheme 51. Synthesis of the Mo2 Phosphonate Cage, [{(η5-C5Me5)Mo}{PhPO(OH)2}]2(PhPO3)2(μ-O)2168

Scheme 52. Synthesis of the Dinuclear Complex, [{(η5-C5Me5)W}{PhP(O)(OH)2}]2(PhPO3)2(μ-O)2168

(Figure 48), which served as the precursor for the preparation of the octa- and the dodecanuclear derivatives.170 The hexanuclear precursor has an edge-sharing bitetrahedral core where the body of the core contains the CrIII ions, and the wings, the CoII ions (Figure 48).170 In the octanuclear phosphonate complex, the four CoII ions are arranged in a square plane; this motif is linked on either end with a pair of dinuclear CrIII units. The phosphonate ligands, in a 5.221 coordination mode, hold the tetranuclear CoII array together. The dodecanuclear complex has two edge-sharing [Co4Cr2] hexagons. Two phosphonate ligands, in a 6.222 mode, one each, hold the hexagons together, while four other phosphonates bind in a chelating manner (Figure 49).170 Several Cr I II /Ln III complexes, [Cr III 6 Ln II I 2 (μ 3 -O) 2 (H2O)2(O3PBu-t)4(O2CBu-t)12(HOBu-i)2(i-PrNH2)2] (LnIII = La, Tb, Dy, Ho) and [CrIII6GdIII2(μ3-O)2(H2O)2(O3PBut)4(O2CBu-t)12(HOBu-i)4], have been prepared utilizing the trinuclear oxo-centered chromium complex [CrIII3(μ3-O)(O2CBu-t)6(H2O)3][O2CBu-t]·3H2O as the starting material.171 The structure of these compounds reveals that this triangular chromium motif is preserved in the complex (Figure 50).171 Two such units are connected to each other by means of phosphonate ligands and the two lanthanide ions. While two of the phosphonates bind in a 4.211 mode, the other pair binds in a 3.111 mode. All of the phosphonate ligands are involved in coordination to the CrIII and the LnIII ions. All of the reported Cr/Mn, Cr/Co, and Cr/Ln phosphonates are listed in Table 11.169−171

Figure 51. A tetranuclear molybdenum phosphonate [(C2H5)2NH2]4[MoV4O8(O3PC(C3H6NH3)(O)PO3)2]·6H2O.172 Adapted from ref 172. Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

assist in stitching the tetranuclear ensemble together. One representative compound is shown in Figure 47. Another family of 3d/3d complexes, such as the one described above, is provided by [CoII4CrIII2(μ4-O)2(O2CBu-t)10(Me2CO)2], [Co4Cr4(μ3-OH)4(O3PBu-t)2(O2CBu-t)6(μ-OEt) 4 (OEt) 2 (HO 2 CBu-t) 4 ]·(EtOH) 0.8 , and [Co 8 Cr 4 (μ 3 OMe) 2 (O 3 PBu-t ) 4 (O 2 CBu-t ) 8 (μ-OMe) 1 0 (HOMe) 6 ]· (MeOH)1.6.170 The reaction of the trinuclear chromium complex [Cr3(μ3-O)(O2CBu-t)6(H2O)3]·(O2CBu-t) with the dinuclear CoII complex [Co2(μ-OH2)(O2CBu-t)4(HO2CBu-t)4] afforded the hexanuclear derivative [CoII4CrIII2(μ4-O)2(O2CBu-t)10(Me2CO)2]

9.2. Molybdenum

All of the molybdenum phosphonates, save one, involve polyoxomolybdate motifs (Table 12).172−177 The lone exception

Figure 52. A hexanuclear molybdenum phosphonate (NH4)6[(MoV2O4)(MoVI2O6)2(O3PC(C3H6NH3)(O)PO3)2]·12H2O.172 Adapted from ref 172. Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA. AH


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Review

Figure 53. Molecular structure of (n-Bu4N)4[{PW9O34{PhPO3}2}2{Zr(DMF)(μ-OH)}2].179 Adapted from ref 179. Copyright 2011 American Chemical Society.

Table 13. Molecular Heteropolyoxotungstates reactants 5

(η -C5Me5)WCl4, PhPO3H2 WO3·H2O, H2O2, MePO3H2, (NMe4)Cl (n-Bu4N)3Na2[PW9O34{PO(Et)}2], ZrOCl2·8H2O (n-Bu4N)3Na2[PW9O34{PO(Ph)}2], ZrOCl2·8H2O (n-Bu4N)3Na2[PW9O34{(t-Bu)PO}2], ZrOCl2·8H2O, La(NO3)3·6H2O

compounds 5

[{(η -C5Me5)W}{PhP(O)(OH)2}]2(PhPO3)2(μ-O)2 [NMe4]3[(MePO3){MePO2(OH)}W6O13(O2)4(OH)2(H2O)]· 4H2O (n-Bu4N)4[{PW9O34{PO(Et)}2}2{Zr(H2O) (μ-OH)}2]·xH2O (n-Bu4N)4[{PW9O34{PO(Ph)}2}2{Zr(DMF)(μ-OH)}2] (n-Bu4N)2[PW9O34{(t-Bu)PO}2{La(DMF)5(H2O)}]·2H2O


ref

dinuclear hexanuclear

168 178

decanuclear -do-do-

179 179 179

dimolybdenum core where the two molybdenum centers are connected to each other by two μ-O bridges affording a four-membered ring. Two phosphonate ligands bridge the two molybdenum centers to give an A-type framework. Two neutral phosphonic acids are suggested to bind, one each to the two molybdenum centers in a η1 manner through the PO unit.168 Homonuclear tetra- and hexanuclear molybdenum phosphonates, [(C2H5)2NH2]4[MoV4O8(O3PC(C3H6NH3)OPO3)2]· 6H2O and (NH4)6[(MoV2O4)(MoVI2O6)2(O3PC(C3H6NH3)(O)PO3)2]·12H2O, are known.172 These complexes have been prepared in the reaction of [MoV2O4(H2O)6]2+/[MoVIO4]2− and H2O3PC(C3H6NH2)(OH)PO3H2 under hydrothermal conditions. The tetranuclear complex possesses a butterfly shaped core with a Mo2O2 motif (Figure 51).172 The hexanuclear derivative contains a central unit of two MoIV ions containing on either side a pair of MoIV ions. Four phosphonate ligands are involved in holding the ensemble together (Figure 52).172 The heteropolymolybdates Rb4KNa[(O2CCH2PO3)2Mo5O15]·H2O and Rb4KNa[(O2CC2H4PO3)2Mo5O15] have been prepared in the reaction of Na2MoO4 with phosphonoacetic acid, HO 2 CCH 2 PO 3 H 2 , or phosphonopropionic acid, HO2CCH2CH2PO3H2. The hexaanionic complex contains five MoO6 octahedra that are bound to each other via four edge junctions and one corner junction.172 The two phosphonates bind to the top and bottom faces of the polyoxomolybadate motif leaving the carboxylate ends free. High-nuclearity organophosphonate-based polyoxomolybdates including 12-, 20-, and 24-molybdophosphonates (NH 4 ) 5 Na 4 [{Mo 6 O 15 (HO 3 PC 6 H 5 )(O 3 PC 6 H 5 )} 2 ]·6H 2 O,

Figure 54. A mononuclear MnII phosphonate, [Mn(t-BuPO3H)2(phen)2]·MeCO2H].183

F i g u r e 5 5 . A di n u c l e a r m a n g a ne se ( I I ) p h o sp h o n a t e , [Mn2(t-BuPO3H)4(phen)2].36

involves [{(η5-C5Me5)Mo}{PhPO(OH)2}]2(PhPO3)2(μ-O)2 and is prepared in the reaction of (η5-C5Me5)MoCl4 with PhP(O)(OH)2 (Scheme 51).168 This compound consists of a AI


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Table 14. Molecular Manganese Phosphonates reactants Mn(O2CMe)2·H2O, t-BuPO3H2, MeCO2H, phen 1-hydroxyethylidenediphosphonate acid (hedpH4), Mn (O2CMe)2·4H2O MnCl2·4H2O, phen, t-BuPO3H2 2-carboxyethyl (phenyl)phosphonic acid)(LH3)Mn (O2CMe)2·4H2O, phen MnCl2·4H2O, {(C7H5N2)CH2}2NCH2PO3H2 t-BuPO3H2, Mn(O2CMe)2·4H2O, bipy, MeCOOH H3L = m-HO3S−C6H4−PO3H2, Mn(ClO4)2·4H2O, NaOH, phen H4L = 1,4,8,11-tetraazacyclotetradecane-1,8- bis (methylphosphonic acid)) (1,8-H4te2p), MnCO3 2-fluoro phenylphosphonic acid, [Mn(salen)(H2O)]2·(ClO4)2 4-fluoro phenylphosphonic acid, [Mn(salen)(H2O)]2·(ClO4)2 [Mn(5-Brsalen)(H2O)]2·(ClO4)2, C10H7PO3H2, NEt3, N,Nethylenebis(5-bromosalicylideneiminate)dianion (5-Brsalen) Mn(ClO4)2·4H2O, phen, C5H9PO3H2

compounds


ref

[Mn(t-BuPO3H)2(phen)2]·MeCO2H Mn(hedpH2)3·3NH2(CH3)2NH(CH3)3·3H2O

mononuclear -do-

183 211

[Mn2(t-BuPO3H)4(phen)2]·2DMF

36

[Mn(L)(phen)(H2O)]2·2H2O

dinuclear/eight-membered ring -do-

Mn2[{(C7H5N2)CH2}2NCH2PO3]2·(H2O)2·2H2O [Mn2(t-BuPO3H)4(bipy)2] [Mn2(HL)2(phen)4][Mn2(HL)2(phen)4(H2O)]2·6H2O [{(H2O)5Mn}2(μ-H2L)](H2L)·21H2O

-do-do-do-do-

186 185 184 213

[Mn2(salen)2(2-FC6H4PO3H)]·(ClO4) ·0.5CH3OH [Mn2(salen)2(4-FC6H4PO3H)]·(ClO4) [Mn2(5-Brsalen)2(C10H7PO3H)2]·2CH3OH

-do-do-do-

190 190 191

[Mn3(C5H9PO3)2(phen)6]·(ClO4)2·7CH3OH

trinuclear/propellane-type framework -do-

36

212

Mn(ClO4)2·4H2O, 2,6-bis(pyrazol-3-yl)pyridine (dpzpy), t-BuPO3H2 Mn(ClO4)2·4H2O, phen, t-BuPO3H2

[Mn3(t-BuPO3)2(dpzpy)3]·(ClO4)2·H2O

Mn(ClO4)2·4H2O, phen, C5H9PO3H2 Mn(OAc)2·4H2O, Ph3CPO3H2 m-HO3S−C6H4−PO3H2 (H3L), Mn(ClO4)2·4H2O, NaOH, phen MePO3H2, (n-Bu)4NMnO4, MeCO2H, Mn(O2CMe)2·4H2O, bipy

[Mn4(C5H9PO3)2(phen)8(H2O)2]·(ClO4)4 [Mn4(O)(Ph3CPO3)4Py4] [Mn4(L)2(phen)8(H2O)2][ClO4]2·3H2O [Mn4O2(MePO3)2(O2CMe)4(bipy)2]·4MeCOOH

MePO3H2, (n-Bu)4NMnO4, PhCO2H, Mn(O2CPh)2·2H2O, phen EtPO3H2, (n-Bu)4NMnO4, bipy, MeCO2H, Mn(O2CMe)2·4H2O n-BuPO3H2, (n-Bu)4NMnO4, bipy, MeCO2H, Mn (O2CMe)2·4H2O, (CO2H)2·2H2O (n-Bu)4NMnO4, t-BuPO3H2, bipy, Mn(O2CMe)2·4H2O, MeCO2H (n-Bu)4NMnO4, t-BuPO3H2, bipy, Mn(O2CPh)2·2H2O, PhCO2H HO2CCH3, (n-Bu)4NMnO4, H2O3PC6H11, phen, Mn (O2CCH3)2·4H2O (n-Bu)4NMnO4, H2O3PC6H11, bipy, Mn(O2CPh)2·2H2O, HO2CPh C6H11PO3H2, [(n-Bu)4N]2Cr2O7, Mn(O2CPh)2·2H2O, HO2CPh, bipy C6H11PO3H2, [(n-Bu)4N]2Cr2O7, Mn(O2CPh)2·2H2O, HO2CPh, phen Mn(O2Ac)2·4H2O, CH3CO2H, C6H11PO3H2, [(n-Bu)4N]2Cr2O7, bipy Mn(O2Ac)2·4H2O, CH3CO2H, [(n-Bu)4N]2Cr2O7, bipy, 2-pyridylphosphonic acid Mn(O2Ac)2·4H2O, CH3CO2H, [(n-Bu)4N]2Cr2O7, phen, 2-pyridyl phosphonic acid Mn(O2Ac)2·4H2O, CH3CO2H, C6H11PO3H2, [(n-Bu)4N]2Cr2O7, Mn(O2CPh)2·2H2O, HO2CPh, phen, 2-pyridyl phosphonic acid MnCl2·4H2O, t-BuPO3H2, NEt3

[Mn4O2(MePO3)2(O2CPh)4(phen)2]·4PhCO2H·2MeCN [Mn4O2(EtPO3)2(O2CMe)4(bipy)2]·7H2O [Mn4O2(n-BuPO3)2(O2CMe)4(bipy)2]·4H2O·(COOH)2

tetranuclear/open-book structure -do-do-dotetranuclear; butterfly shaped -do-do-do-

[Mn4O2(t-BuPO3)2(MeCO2)4(bipy)2]

-do-

193

[Mn4O2(t-BuPO3)2(PhCO2)4(bipy)2] [Mn4O2(O2CCH3)4(O3PC6H11)2(phen)2]

-do-do-

193 205

[Mn4O2(O2CPh)4(O3PC6H11)2(bipy)2]

-do-

205

[Mn3CrO2(O2CPh)4(O3PC6H11)2(bipy)2]

-do-

169

[Mn3CrO2(O2CPh)4(O3PC6H11)2(phen)2]

-do-

169

[Mn3CrO2(O2CCH3)4(O3PC6H11)2(bipy)2]

-do-

169

[Mn3CrO2(O2CCH3)4(O3PC5H4N)2(bipy)2]

-do-

169

[Mn3CrO2(O2CCH3)4(O3PC5H4N)2(phen)2]

-do-

169

[Mn3CrO2(O2CPh)4(O3PC5H4NO)2(phen)2]

-do-

169

[(HPiv)12Mn4(μ3-O3PBu-t)4]

tetranuclear; D4R coreshaped pentanuclear; basketshaped -dohexanuclear -do-do-

182

193 46 197 191

-do-

184

heptanuclear octanuclear nonanuclear

198 12 199

decanuclear -doheterometallic decanuclear

182 206 198

(n-Bu)4NMnO4, t-BuPO3H2, phen, Mn(O2CMe)2·4H2O, MeCO2H (n-Bu)4NMnO4, t-BuPO3H2, phen, Mn(O2CPh)2·2H2O, PhCO2H [Mn3O(O2CPh)6(py)2(H2O)], Ph(H)PO2H [Mn3O(PhCO2)6(py)2(H2O)], pyridine, PhPO3H2 [Mn(5-Brsalen)(H2O)]2·(ClO4)2, C10H7PO3H2, NEt3, [5-Brsalen = N,N-ethylenebis(5-bromosalicylideneiminate) dianion] m-HO3S−C6H4−PO3H2 (H3L), Mn(ClO4)2·4H2O, NaOH, phen [Mn3O(O2CCMe3)6(py)3], PhPO3H2, NaOMe Mn(O2CMe)2, (NH4)2[Ce(NO3)6], t-BuPO3H2, MeCO2H t-BuPO3H2, CH3CO2H, Mn(O2CMe)2·4H2O, NaOMe, (n-Bu)4NMnO4 MnCl2·4H2O, t-BuPO3H2, NEt3 [Mn3O(O2CC6H5)6(py)2(H2O)], C10H7PO3H2 [Mn3O(O2CCMe3)6(py)3], PhPO3H2, NaOMe, Na2(O3PPh)

[Mn4(t-BuPO3)2(t-BuPO3H)2(phen)6(H2O)2]·(ClO4)2

[Mn5O3(t-BuPO3)2(MeCO2)5(H2O)(phen)2] [Mn5O3(t-BuPO3)2(PhCO2)5(phen)2] [Mn6O2(O3PPh)2(O2PHPh)2(O2CPh)8(py)2] [Mn6III(O)2(PhCO2)8(PhPO3)2(PhPO3H)2(py)2] [Mn6(5-Brsalen)6(C10H7PO3)2(H2O)2]·(ClO4)2·7.6H2O [Mn6(L)4(phen)8(H2O)2]·4H2O; [Mn6(L)4(phen)8(H2O)2]·24H2O; [Mn6(L)4(phen)6(H2O)4]·5H2O; [Mn(phen) (H2O)4]2[Mn4(L)4(phen)4]·10H2O [Mn7(μ3-O)3(O3PPh)3(O2CCMe3)8(py)3] [Ce2Mn6O6(OH)5(t-BuPO3)6(O2CMe)3]·53H2O [Mn9O6(t-BuPO3)2(O2CMe)11(MeCO2H)(H2O)]·8H2O [(HPiv)8Mn10(μ-Cl)4(μ5,η2-O3PBu-t)4(μ-Piv)8] [MnII8MnIII2O2(O3PC10H7)4(C6H5CO2)10(py)4(H2O)2] [Mn9Na(μ3-O)4(μ4O)2(O3PPh)2(O2CCMe3)12(H2O)2(H2O)0.67(Py)0.33] AJ

36 36 36 45 184 204 204 204 204

193


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Table 14. continued reactants [MnII(O2CBu-t)4(EtOH)]n, [Ln2(O2CBu-t)6(HO2CBu-t)6] (Ln = Gd, Dy), PhCH2PO3H2 C6H9PO3H2, bipy, CH3CO2H, Mn(MeCO2)2·4H2O, (n-Bu)4NMnO4 C6H9PO3H2, Mn(PhCO2)2·2H2O, (n-Bu)4NMnO4, bipy, PhCO2H, C6H9PO3H2, Mn(PhCO2)2·2H2O, phen, PhCO2H, (n-Bu)4NMnO4 t-BuPO3H2, CH3CO2H, Mn(O2CMe)2·4H2O, NaOMe, NaN3, n-Bu4NMnO4 [Mn3O(O2CCMe3)6(py)3], PhPO3H2, NaOMe, Na2(O3PPh) MnCl2·4H2O, t-BuPO3H2, NEt3, NaPiv [Mn3O(O2CCH3)6(py)3]ClO4, C6H11PO3H2, pyridine [Mn3O(O2CC6H5)6(py)2(H2O)], C10H7PO3H2 MnCl2·4H2O, KMnO4, NEt3, t-BuPO3H2 MnCl2·4H2O, KMnO4, NEt3, t-BuPO3H2, 2-aminopyridine (C5H7N2) PhCH2PO3H2, pyridine, [Mn3O(PhCO2)6(py)2(H2O)] PhPO3H2, KMnO4, PhCO2H, N(CH2CH2OH)3 (Htea) MnCl2·4H2O, KMnO4, t-BuPO3H2, 2-aminopyridine (C5H7N2) (n-Bu)4NMnO4, MePO3H2, MeCO2H, Mn(O2CMe)2·4H2O Ph2CHPO3H2, [Mn3O(Me3CCO2)6(Py)3] [Mn3O(O2CCMe3)6(py)3], PhPO3H2, NaOMe [MnII(O2CBu-t)4(EtOH)]n, [Ln2(O2CBu-t)6(HO2CBu-t)6] (Ln = Gd, Dy), MePO3H2 (Ph(Me)2)PO3H2 [Mn3O(Me3CCO2)6(Py)3] PhCH2PO3H2, Me3CCO2H, pyridine, Et3N, [Mn3O (O2CPh)6(py)3]ClO4 MnCl2·4H2O, t-BuPO3H2, NEt3 [Mn3O(O2CCH3)6(py)3]ClO4, C6H11PO3H2, pyridine t-BuPO3H2, MeCO2H, Mn(O2CMe)2·4H2O, phen H2O3PCH2Ph, pyridine, [Mn3O(O2CPh)6 (py)3]ClO4, [Mn3O (O2CPh)6 (py)2(H2O)], Et3N PhCH2PO3H2, pyridine, [Mn3O(O2CPh)6(py)3]ClO4, [Mn3O (O2CPh)6 (py)2(H2O)], Et3N

compounds


ref

[MnII4GdIII6(O3PCH2Ph)6(HO2CBu-t)13(O2CMe3)(HO2CBu-t)(OH) -do(MeCN)2; [MnII6DyIII6(μ3OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCN)5] [Mn12O8(O2CMe)6(O3PC6H9)7(bipy)3] dodecanuclear

196

[Mn12O8(O2CPh)6(O3PC6H9)7(bipy)3]

-do-

203

[Mn12O8(O2CPh)6(O3PC6H9)7(phen)3]

-do-

203

[n-Bu4N][Mn13O6(t-BuPO3)10(OH)2(N3)6(MeCO2H)2(H2O)2]·6H2O

-do-

199

[MnIII13(μ3-O)8(OMe)8(O3PPh)4(O2CCMe3)10] [MnIIMnIII12(μ4-O)6(μ-OH)6(O3PBut)10(OH2)2(DMF)4]·[2MeOH·4DMF] [MnIIMn12IIIO6(OH)6(O3PC6H11)10(py)6] [MnII4MnIII9O4(OH)2(O3PC10H7)10(C6H5CO2)5(py)8(H2O)6] [MnIIMnIII12(μ4-O)8(μ4-Cl)6(t-BuPO3)8][MnIICH3CN)6]·Cl2 ·6CH3CN·5.25H2O (C5H7N2)3[MnII3MnIII10(μ4-O)6(μ3-O)(μ3-OH)(μ4-Cl)4(Cl)(tBuPO3H)(t-BuPO3)9]·3CH3CN·2H2O [LiMnIII10MnII2(μ3-O)4(PhCH2PO3)4(OMe)4(PhCO2)15(py)2] [K3Mn10(PhCOO)10(PhPO3)2(Htea)6](PhCOO)·6MeCN}n (C5H7N2)[MnII3MnIII11(μ4-O)6(μ3-O)(μ3-OH)(μ2-OH)(μ4-Cl)4(tBuPO3H)(t-BuPO3)10(2-amino-pyridine)·(C5H6N2)·3CH3CN·2H2O [Mn15O6(MePO3)2(MeCO2)18(H2O)12][MePO3H]2·12H2O [Mn16(Ph2CHPO3)8(μ4-O)6(μ3O)2(OMe)4(HOMe)2(Me3CCO2)6(OH2)(Py)2] [MnIII16MnIV2(μ3-O)8(PhPO3)14(O2CCMe3)12(py)6(H2O)2] [MnII9GdIII9(O3PMe)(O2CBu-t)18(μ3-OH)1.5(O2CBu-t)1.5]

-dotridecanuclear

198 208

-do-do-do-

180 206 209

-do-

209

-do-dotetradecanuclear

197 207 209

pentadecanuclear hexadecanuclear

183 210

octadecanuclear heterometallic octadecanuclear nonadecanuclear icosanuclear

198 196

icosanuclear; distorted cylinder docosanuclear tetraicosanuclear -do-

182

hexaicosanuclear

181

[Mn19(μ4-O)6(μ3-O)2(O2CCMe3)10(OCH3)16(O3P(Ph(Me)2))6] [Et3NH]2[MnIII18MnII2(μ4-O)8(μ3-O)4(μ3OH)2(O3PCH2Ph)12(O2CCMe3)10(py)2] [(HPiv)8(H2O)8Mn20(μ-OH)2(μ-Cl)2(μ5,η2-O3PBu-t)2(μ4,η2-O3PBu-t)6 (μ5-O3PBu-t)4(μ3-Piv)2(μ-Piv)10] [Mn4IIMn18IIIO12(O3PC6H11)8(O2CCH3)22(H2O)6(py)2] [Mn20Na4O12(t-BuPO3)12(O2CMe)16(H2O)12]·5H2O K4[MnIII16MnII4(μ4-O)4(μ3-O)6 (PhCH2PO3)14(PhCO2)12(PhCO2H)0.5(CH3CN)2] Na6[MnIII14MnII6(μ4-O)4(μ3-O)4 (OH)4(PhCH2PO3)14(PhCO2)12(PhCO2H)2(H2O)4(CH3CN)4]

203

210 181

180 183 181

(Figure 53).179 The examples of heteropolyoxotungstates are listed in Table 13.168,178,179

Na24[Na4(H2O)6{(Mo2O4)10(O3PCH2PO3)10(CH3CO3)8(H2O)4}]· 103H2O, and Na5[H7{N(CH2PO3)3}Mo6O16(OH)(H2O)4]4· 18H2O are stabilized by di- and triphosphonate ligands.174−177

10. GROUP 7 PHOSPHONATES

9.3. Tungsten

10.1. Manganese

The number of tungsten phosphonates is extremely limited. The dinuclear compound, [{(η 5 -C 5 Me 5 )W][PhP(O)(OH)2}]2(PhPO3)2(μ-O)2, prepared from the reaction of (η5-C5Me5)WCl4 and PhPO3H2 possesses a structure similar to that of the analogous molybdenum derivative that was discussed above (Scheme 52).168 The reaction of WO3·H2O, H2O2, and MeP(O)(OH)2 in the presence of NMe4Cl afforded the hexanuclear complex [NMe4]3[(MePO3){MePO2(OH)}W6O13(O2)4(OH)2(H2O)]· 4H2O.178 Two tungsten centers are hexacoordinate, while four others are heptacoordinate. The molecule contains two trinuclear units that are connected with each other through oxo bridges. While in one trinuclear unit the [MePO3]2− binds to the three tungsten centers in a 3.111 mode, in the other trinuclear unit the [MeP(O)2(OH]− binds to only two tungsten centers in a 2.110 mode. Heteropolyoxotungstates are also known such as (n-Bu4N)4[{PW9O34{PO(R)}2}2{Zr(DMF)(μ-OH)}2] (R = Ph), which contains two nonanuclear motifs [PW9O34{PO(R)}2]5− linked by a [(DMF)Zr(μ-OH)2Zr(DMF)]6+ unit

Molecular manganese phosphonates have been studied extensively. The nuclearity of homonuclear molecular manganese phosphonates varies from 1 to 22;180 in heterometallic systems the highest nuclearity observed is 26.181 Homovalent complexes containing MnII or MnIII are well-known. Mixedvalent MnII/MnIII or MnIII/MnIV complexes are also known. Interestingly, most of the reported mixed-valent manganese phosphonate complexes seem to contain carboxylate or other bridging ligands in addition to phosphonate ligands. 10.1.1. MnII. As mentioned above, the nuclearity of MnII phosphonates varies from 1 to 20.182 These are discussed below. Discrete MnII complexes containing only phosphonate ligands (without carboxylate ligands) are in fact only a handful: [Mn(t-BuPO 3 H) 2 (phen) 2 ]·MeCO 2 H], 1 83 [Mn 2 (HL) 2 (phen)4],184 [Mn2(HL)2(phen)4][Mn2(HL)2(phen)4(H2O)]2· 6H 2 O, 1 84 [Mn 4 (L) 2 (phen) 8 (H 2 O) 2 ][ClO 4 ] 2 ·3H 2 O, 1 84 [Mn 6 (L) 4 (phen) 8 (H 2 O) 2 ]·4H 2 O, 184 [Mn 6 (L) 4 (phen) 8 (H2O) 2]·24H2 O,184 and [Mn6(L) 4(phen)6(H2O) 4]·5H2O AK


Chemical Reviews

Review

[LH3 = (m-HO3S−C6H4−PO3H2); phen = 1,10-phenanthroline].184 In other cases, either carboxylate or other ancillary ligands are present within the clusters. A mononuclear MnII phosphonate derivative, [Mn(tBuPO3H)2(phen)2]·MeCO2H], was prepared in the reaction of Mn(O2CMe)2·4H2O, MeCO2H, t-BuPO3H2, and 1,10phenanthroline (phen) (Figure 54).183 In this compound, MnII has in its coordination periphery two 1,10-phenanthroline and two monodentate [t-BuPO3H]− ligands. Recently, we have synthesized a series of carboxylate-free molecular di-, tri-, and tetranuclear manganese(II) phosphonates containing ancillary nitrogen ligands (Figure 55).36 The di-, tri-, and tetranuclear ensembles were prepared in the reaction of manganese(II) salts [MnCl2·4H2O or Mn(ClO4)2· 4H2O] with various organophosphonic acids [cyclopentylphosphonic acid (C5H9PO3H2) or tert-butylphosphonic acid (t-BuPO3H2)] and chelating nitrogen ligands [1,10-phenanthroline or 2,6-bis(pyrazol-3-yl)pyridine (dpzpy)].36 The dinuclear MnII derivative, [Mn2(t-BuPO3H)4(phen)2], contains two isobidentate phosphinate [t-BuP(O)2OH]− ligands, two unidentate phosphinate ligands, [t-BuP(O)2OH]−, and two 1,10phenanthroline ligands. Two manganese centers are bridged to each other by two bridging [t-BuP(O)2OH]− ligands, forming an eight-membered (Mn2P2O4) puckered ring. Each MnII center in the dinuclear system is 5-coordinate with a distorted squarepyramidal geometry. The molecular structure of this dinuclear compound is similar to that found in other related compounds, [Mn 2 (m-HO 3 S−C 6 H 4 −PO 3 ) 2 (phen) 4 ], 18 4 [Mn 2 (t-BuPO 3 H) 4 (bipy) 2 ), 185 Mn 2 {[(C 7 H 5 N 2 )CH 2 ] 2 NCH 2 PO 3 } 2 (H2O)2·2H2O {[(C7H5N2)CH2]2NCH2PO3H2 = bbimpH2}186 [Cu 2 (μ2 -C 5 H 9 PO 3 ) 2 (bpya)2 (H2 O) 2 ](H 2 O) 4 ),187 [bpya = 2,2-bipyridylamine], [Cd2(ArPO3H)4(bipy)2]·CH3OH·H2O188 (Ar = 2,4,6-i-Pr3−C6H2), and [In2(t-BuPO3H)4(phen)2Cl2)89 [Mn(bipy)2(dippH)]2·2ClO4·2CH3OH (dippH2 = 2,6-diisopropylphenyl phosphate).189 Another family of dinuclear derivatives contains salen as the bridging ligand while the phosphonates occupy terminal positions: [Mn2(salen)2(2-FC6H4PO3H)]·(ClO4), [Mn2(salen)2(4-FC6H4PO3H)]·(ClO4), and [Mn2(5-Brsalen)2(C10H7PO3H)2]· 2CH 3 OH [5-Brsalen = N,N-ethylenebis(5-bromosalicylideneiminate)dianion] (Table 14).190,191 The trinuclear complexes, Mn3(C5H9PO3)2(phen)6](ClO4)2· 7CH3OH and [Mn3(t-BuPO3)2 (dpzpy)3]·(ClO4)2·H2O, possess nearly similar structural cores (Figure 56). 36 In [Mn3(C5H9PO3)2(phen)6]·(ClO4)2·7CH3OH, manganese

Figure 57. Tetranuclear MnII phosphonates, (a) [Mn4(t-BuPO3)2(tBuPO3H)2(phen)6(H2O)2]·(ClO4)2 and (b) [Mn4(C5H9PO3)2(phen)8(H2O)2]·(ClO4)4.36

Figure 58. A tetranuclear MnII phosphonate core of [(HPiv)12Mn4(μ3O3PBu-t)4] in a distorted cubic topology.182 Adapted from ref 182. Copyright 2014 The Royal Society of Chemistry.

is hexacoordinate, while in [Mn3(t-BuPO3)2(dpzpy)3]·(ClO4)2· H2O it is pentacoordinate. The core structures in both of these compounds are comprised of a triangular Mn3 platform being

Figure 56. A trinuclear manganese phosphonate, [Mn3(C5H9PO3)2(phen)6]·(ClO4)2.36 AL


Chemical Reviews

Review

Figure 59. A decanuclear MnII phosphonate complex, [(HPiv)8Mn10(μ-Cl)4(μ5,η2-O3PBu-t)4(μ-Piv)8].182 Adapted from ref 182. Copyright 2014 The Royal Society of Chemistry.

Figure 60. {3 × 3} grid-containing heterometallic MnII4GdIII6 complex, [Mn II 4 Gd III 6 (O 3 PCH 2 Ph) 6 (HO 2 CBu-t) 13 (O 2 CMe 3 )(HO2CBu-t)(OH)(MeCN)2].196 Adapted from ref 196. Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 61. Molecular structure of a {MnII6DyIII6} phosphonate, [MnII6DyIII6(μ3-OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCN)5].196 Adapted from ref 196. Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

held together by two bicapping tripodal phosphonate ligands. This results in the formation of a propellane-type bicyclic structure. Such a structural motif is also present in [Zn3Cl2(3,5-Me 2 Pz) 4 (t-BuPO 3 ) 2 ] 1 9 2 (discussed below) and [In3(C5H9PO3)2(C5H9PO3H)4(phen)3]·NO3·3.5H2O89 (discussed above). Bicapping coordination mode of the phosphonate ligand has been observed in tetranuclear metal phosphonate clusters such as [Mn4O2(t-BuPO3)2(RCO2)4(bipy)2] (R = Me, Ph).193 Tetranuclear derivatives, [Mn4(t-BuPO3)2(t-BuPO3H)2(phen) 6 (H 2 O) 2 ]·(ClO4 ) 2 and [Mn 4 (C 5 H 9 PO 3 ) 2 (phen) 8 (H2O)2]·(ClO4)4, are shown in Figure 57.36 In this compound, four MnII ions are held together by four bridging phosphonate ligands. As a result, a tricyclic system is generated, which contains three fused Mn2P2O4 eight-membered rings. All of the rings are puckered, and the relationship of the two terminal rings vis-à-vis the central ring is trans (Figure 57a).36 Similar types of structural forms are also known in the

ZnII phosphonate system, [Zn4{ArPO3}2{ArPO2(OH)}2{DMPZH}4(DMPZ)2]·5MeOH (Ar = 2,4,6-i-Pr3−C6H2).194 On the other hand, another tetranuclear complex, [Mn4(C5H9PO3)2(phen)8(H2O)2]·(ClO4)4, possesses a central dinuclear motif containing an eight-membered Mn2P2O4 ring (Figure 57b).36 In this structure, the bridging phosphonate ligands are present in the central region. A similar type of manganese phosphonate cage, [Mn 4 (m-HO 3 S−C 6 H 4 − PO3H2)2(phen)8(H2O)2]·(ClO4)2·3H2O, is also known in the literature (Table 14).184 Recently, a cubic tetranuclear MnII phosphonate, [(HPiv)12Mn4(μ3-O3PBu-t)4], was prepared in the reaction involving MnCl2·4H2O, t-BuPO3H2, and NaPiv. The core of this complex has a distorted cube type shape (Figure 58).182 Alternate vertices of the cubic core are occupied by phosphorus and manganese atoms. This structural type is quite common and has been found in other transition metal and main-group metal AM


Chemical Reviews

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Figure 62. A butterfly-shaped core of [Mn4O2(t-BuPO3)2(RCO2)4(bpy)2]. Notice that the four MnIII ions are present in a plane. Three MnIII centers, each, are capped by a [t-BuPO3]2− ligand.193 Adapted from ref 193. Copyright 2008 American Chemical Society. Figure 64. A basket-like core of [MnIII5O3(t-BuPO3)2(MeCO2)5(H2O)(phen)2].193 Adapted from ref 193. Copyright 2008 American Chemical Society.

phosphonates and phosphates. For example, the manganese(II) phosphate [Mn4(dipp)4(bipy)4] (dipp = 2,6-diisopropylphenyl phosphate) also possesses a similar type of structure.189 A hexanuclear manganese phosphonate cage, [Mn6(L)4(phen)8(H2O)2]·4H2O, was prepared utilizing the reaction of MnII salts with m-HO3S−C6H4−PO3H2 under hydrothermal conditions.184 The structural analysis of this compound reveals that two terminal MnII ions are trans to each other with respect to a central Mn4 plane. A similar structural motif is found in the ZnII cage, [Zn6(m-O3S-Ph-PO3)4(phen)8]·11H2O.195 As mentioned above, the reaction of MnCl2·4H2O, t-BuPO3H2, and NaPiv afforded the tetranuclear derivative [(HPiv)12Mn4(μ3O3PBu-t)4].182 Decreasing the temperature from 98 to 30 °C resulted in the formation of the decanuclear MnII phosphonate, [(HPiv)8Mn10(μ-Cl)4(μ5,η2-O3PBu-t)4(μ-Piv)8] (Figure 59).182 The decanuclear cage is constructed by multiple coordination action of the μ-Cl, μ-Piv, and [t-BuPO3]2− ligands. Four Cl− ions are involved in bridging two perpendicular tetragonal pyramids (Figure 59). Interestingly, heating the decanuclear compound at 80 °C afforded an icosanuclear MnII phosphonate cluster, [(HPiv)8(H2O)8Mn20(μ-OH)2(μ-Cl)2(μ5,η2-O3PBu-t)2(μ4,η2O3PBu-t)6(μ5-O3PBu-t)4(μ3-Piv)2(μ-Piv)10].182 A heterometallic 3d−4f decanuclear MnII containing phosphonate cage, [Mn II 4 Gd III 6 (O 3 PCH 2 Ph) 6 (HO 2 CBut)13(O2CMe3)(HO2CBu-t)(OH)(MeCN)2], was recently reported (Figure 60).196 This cage contains four MnII and six

GdIII metal ions that are held together by bridging phosphonate and pivalate ligands. This compound was prepared by utilizing cluster expansion strategies in the reaction involving [MnII(O2CBu-t)4(EtOH)]n, [Gd2(O2CBu-t)6(HO2CBu-t)6], with PhCH2PO3H2. The core of [MnII4GdIII6(O3PCH2Ph)6(HO2CBu-t)13(O2CMe3)(HO2CBu-t)(OH)(MeCN)2] reveals that it possesses a distorted [3 × 3] {Mn4Gd6} grid. In this structure, six phosphonates are involved in three different coordination binding modes: 5.322, 4.221, and 3.211. A similar grid-type structure is known for [Co4Gd6] phosphonate cluster (see below).21 An interesting heterometallic dodecanuclear MnII6DyIII6 complex was synthesized utilizing the cluster expansion strategy. Thus, the reaction of [MnII(O2CBu-t)4(EtOH)]n and [Dy2(O2CBu-t)6(HO2CBu-t)6] with PhCH2PO3H2 afforded [Mn II 6 Dy III 6 (μ 3 OH) 2 (O 3 PCH 2 Ph) 6 (O 2 CBu-t) 16 (MeCN)5].196 This compound possesses a truncated spheretype of structure containing phosphorus, manganese, and dysprosium atoms that form a hexagonal bipyramid (Figure 61).196 10.1.2. MnIII. Molecular MnIII phosphonate complexes are also prevalent. The nuclearity of MnIII phosphonate clusters varies between 4 and 24.

Figure 63. A tetranuclear, heterometallic Mn3Cr phosphonate, [Mn3CrO2(O2CCH3)4(O3PC5H4N)2(phen)2].169 Adapted from ref 169. Copyright 2008 American Chemical Society. AN


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Figure 67. Core structure of the nonanuclear MnIII phosphonate, [Mn9O6(t-BuPO3)2(O2CMe)11(MeCO2H)(H2O)]·8H2O.199 Adapted from ref 199. Copyright 2008 The Royal Society of Chemistry.

Figure 65. A hexanuclear MnIII phosphonate/phosphinate cluster, [Mn6O2(O3PPh)2(O2PHPh)2(O2CPh)8(py)2].46 Adapted from ref 46. Copyright 2001 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 66. A heptanuclear homovalent MnIII complex, [Mn7(μ3O)3(O3PPh)3(O2CCMe3)8(py)3].198 Adapted from ref 198. Copyright 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 68. Core structure of the dodecanuclear MnIII phosphonate, [Mn12O8(O2CPh)6(O3PC6H9)7(bipy)3].203 Adapted from ref 203. Copyright 2006 American Chemical Society.

Tetranuclear manganese(III) phosphonate complexes, [Mn4O2(t-BuPO3)2(RCO2)4(bpy)2] (R = Me, Ph), possessing butterfly shapes are known.193 In these compounds, all four MnIII ions are coplanar containing two edge-sharing Mn3O motifs. The two [t-BuPO3]2− ligands cap each of the trinuclear motifs and are placed trans with respect to each other (Figure 62).193 All other tetranuclear manganese phosphonate complexes are summarized in Table 14. A heterometallic tetranuclear Mn3Cr phosphonate cage, [Mn3CrO2(O2CCH3)4(O3PC5H4N)2(phen)2], was prepared utilizing a reaction between Mn(O2Ac)2·2H2O, HO2CMe, 1,10-phenanthroline, 2-pyridyl phosphonic acid, and [(n-Bu)4N]2Cr2O7.169 This compound possesses a [M4(μ3-O)2]8+ core (Figure 63). Crystallographically, CrIII could not be distinguished from MnIII. A pentanuclear MnIII complex, [MnIII5O 3(t-BuPO 3) 2(MeCO2) 5(H 2O)(phen)2], is known, which possesses a

basket-like cage structure.193 This compound was prepared in the reaction of (n-Bu)4NMnO4, Mn(O2CMe)2·4H2O, t-BuPO3H2, 1,10-phenanthroline, and MeCO2H. This complex possesses a [Mn5O3]9+ core where all of the manganese centers are in a +3 oxidation state. The complex is held together by two [t-BuPO3]2− and three μ3-O ligands. Other ligands involved in binding to the core are five MeCO2−, two phen, and one water molecule. The two [t-BuPO3]2− ligands are involved in this pentanuclear cage in 4.211 and 3.111 coordination binding modes (Figure 64). The reaction of the mixed-valent trinuclear oxo cage, [Mn3O(O2CPh)6(py)2(H2O)] (py = pyridine), with phenylphosphonic acid afforded a centrosymmetric, mixed phosphonate/ phosphinate hexanuclear MnIII assembly, [Mn6O2(O3PPh)2(O2PHPh)2(O2CPh)8(py)2].46 Structural analysis of this compound reveals that the oxo-bridged trinuclear manganese core AO


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Figure 69. Molecular structure of [MnIII20Na4O12(t-BuPO3)12(O2CMe)16(H2O)12]·5H2O.183 Adapted from ref 183. Copyright 2009 The Royal Society of Chemistry.

Figure 70. A heterometallic octanuclear CeIV2MnIV6 core, present in [Ce2Mn6O6(OH)5(t-BuPO3)6(O2CMe)3]·53H2O.12 Adapted from ref 12. Copyright 2010 The Royal Society of Chemistry.

Figure 72. A mixed-valent decanuclear manganese phosphonate, [MnII8MnIII2O2(O3PC10H7)4(C6H5CO2)10(py)4(H2O)2].206 Adapted from ref 206. Copyright 2009 The Royal Society of Chemistry.

[PhPO3]2− and two [PHPhO2]− ligands (Figure 65). A direct reaction involving PhPO3H2 also afforded a similar complex [MnIII6(O)2(PhCO2)8(PhPO3)2(PhPO3H)2(py)2].197 The reaction of the mixed-valent cage, [Mn 3 O(O2CCMe3)6(py)3], with PhPO3H2 in the presence of pyridine and triethylamine as the base afforded a heptanuclear manganese(III) phosphonate cage, [Mn7(μ3-O)3(O3PPh)3(O2CCMe3)8(py)3].198 Interestingly, in this compound the two types of structural motifs described above, the oxocentered Mn3O triangle and the butterfly shaped Mn4O2 core, are linked by [PhPO3]2− and [t-BuCO2]− ligands (Figure 66).198 A nonanuclear homovalent manganese(III) phosphonate complex, [Mn9O6(t-BuPO3)2(O2CMe)11(MeCO2H)(H2O)]· 8H2O, is known whose core is shown in Figure 67.199 The latter consists of two [Mn3O] units linked to a near linear [Mn3] unit by four μ3-O ligands. The whole cage is put

Figure 71. A mixed-valent tetranuclear [MnII2MnIIII2(O)(Ph3CPO3)4Py4] complex.45

of the starting material is retained in the product. Two such trinuclear Mn3O units are bridged by two in situ-generated AP


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Scheme 53. Synthesis of a Mixed-Valent Tridecanuclear Manganese Phosphonate Cluster, [MnIIMnIII12(μ4-O)6(μ-OH)6(O3PBu-t)10(OH2)2(DMF)4]·[2MeOH·4DMF], Containing a Central MnII and 12 Peripheral MnIII.208

Figure 73. A nonoxido hetero metallic mixed-valent complex, [K 3 Mn I I 6 Mn I I I 4 (PhCO 2 ) 1 0 (PhPO 3 ) 2 (Htea) 6 ] [Htea = N(CH2CH2OH)3], containing a K3MnII6MnIII4 core.207 Adapted from ref 207. Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

together by the multiple coordination action of [t-BuPO3]2− ligands in a 5.221 coordination mode. Another nonanuclear mixed metal complex, [Mn9Na(μ3-O)4(μ4-O)2(O3PPh)2(O2CCMe3)12(H2O)2(H2O)0.67(py)0.33], contains a central manganese atom connected to six Mn sites by four μ3-oxide ligands, which generates four oxo-centered triangles. Two triangular oxo-centered manganese cores are linked by two μ3-oxide ligands to form a heptametallic core. One vertex of the nonanuclear core is occupied by a sodium ion, which is bridged to a μ3-oxide and two carboxylate ligands. Finally, the coordination number of the sodium ion is complete by coordinating two water molecules. The nonanuclear core of [Mn9Na(μ3-O)4(μ4-O)2(O3PPh)2(O2CCMe3)12(H2O)2(H2O)0.67(py)0.33] is present as part of an icosahedron; the other three vertices are occupied by two phosphorus and one sodium atom.198 A similar type of core is also present in the carboxylate cages [Mn9O7(O2CPh)13(py)2],200 [K2Mn9O7(O2CCMe3)15(HO2CCMe3)2],201 and [Na2Mn9O7(O2CPh)15(MeCN)2].202 The reaction of Mn(PhCO 2) 2·2H 2O, NBu 4MnO 4, and C6H9PO3H2 in the presence of the ancillary ligand 2,2′bipyridine afforded a homovalent dodecanuclear MnIII phosphonate cage, [Mn12O8(O2CPh)6(O3PC6H9)7(bipy)3].203 The structure

of this compound is made up of three layers: the upper layer contains a MnIII3O triangular core, which is capped by a [C6H9PO3]2− ligand; the middle layer consists of six MnIII ions bridged by μ3-O and [C6H9PO3]2− ligands; the bottom layer contains three Mn III ions that are bridged by three [C6H9PO3]2− ligands. The inter layer space is occupied by phosphonate/carboxylate or 2,2′-bipyridine ligands (Figure 68).203 The reaction of Mn(O2CMe)2·4H2O, t-BuPO3H2, MeCO2H, and 1,10-phenanthroline afforded a homovalent MnIII phosphonate cluster [Mn 20 Na 4 O 12 (t-BuPO 3 ) 12 (O 2 CMe) 16 (H2O)12]·5H2O.183 The core of this structure contains two folded butterfly like [Mn4(μ3-O)2] units and two trigonal prism [Mn6O6] units that are connected to each other through bridging μ3-O and [t-BuPO3]2− ligands (Figure 69).183 10.1.3. MnIV. Homovalent molecular manganese phosphonates containing MnIV are rare. A heterometallic octanuclear

Figure 74. A mixed-valent manganese phosphonate complex, [LiMnIII10MnII2(μ3-O)4(PhCH2PO3)4(OMe)4(PhCO2)15(py)2].197 Adapted from ref 197. Copyright 2006 The Royal Society of Chemistry. AQ


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CeIV2MnIV6 complex, [Ce2Mn6O6(OH)5(t-BuPO3)6(O2CMe)3]· 53H2O, was prepared in the reaction of Mn(O2CMe)2, (NH4)2[Ce(NO3)6], MeCO2H, and t-BuPO3H2. The octametallic core consists of a central [CeIV2(OH)3] unit connected to three MnIV2O2 units affording three distorted cubane motifs, [CeIV2MnIV2O2(OH)2] (Figure 70).12 10.1.4. MnII/MnIII. The largest number of manganese phosphonates are mixed valent MnII/MnIII complexes. The nuclearity of these complexes varies from 4 to 26.181 Tetranuclear mixed-valent MnII/MnIII phosphonate complexes contain various types of structural motifs: oxo-centered triangle45,46,206/butterfly-shaped193,204,205/cubic-shaped.182 A prominent example where the oxo-centered triangular motif is present is the mixed-valent MnII2MnIII2 complex, [Mn4(O)(Ph3CPO3)4Py4],45 obtained in the reaction of tritylphosphonic acid, CPh3PO3H2, Mn(OAc)2·4H2O, and pyridine (Figure 71). Notice that the triangular Mn3O motif is fused to the fourth manganese center through the 3.111 coordination mode of the phosphonate ligands. An interesting mixed-valent decanuclear manganese phosphonate cage, [MnII8 MnIII2 O 2(O 3PC10 H7 ) 4(C 6H 5CO 2) 10(py)4(H2O)2], was synthesized by a microwave-assisted technique involving [Mn3O(O2CC6H5)6(py)2(H2O)] and C10H7PO3H2.206 The core of this complex is centrosymmetric, containing two equivalent [MnII4O4] units linked by a central [MnIII2O2]. The former consists of four MnII ions connected to each other by one [μ4-O]2− and two [C10H7PO3]2− ligands (Figure 72). An interesting example of a nonoxido heterometallic mixed-valent decanuclear manganese phosphonate cage, [K3MnII6MnIII4(PhCO2)10(PhPO 3)2(Htea)6] [Htea = N(CH2CH2OH)3], was synthesized in the reaction involving KMnO4, PhPO3H2, PhCO2H, and N(CH2CH2OH)3.207 This compound contains six MnII and four MnIII ions and possesses a planar, cyclic, 24-metallacrown-10 like structure, which contains three potassium ions as guests (Figure 73). In the direct reaction of [Mn3O(O2CPh)6(py)2(H2O)] and PhPO3H2, [MnIII6(O)2(PhCO2)8(PhPO3)2(PhPO3H)2(py)2] was obtained as described above.197 Upon changing the reactants to PhCH2PO3H2 and LiOMe, a heterometallic dodecanuclear mixed-valent manganese phosphonate cage [LiMnIII10MnII2(μ3-O)4(PhCH2PO3)4(OMe)4(PhCO2)15(py)2] was obtained (Figure 74).197 The central core of the compound is a hexanuclear Mn6 trigonal prism; two triangular coplanar units are bound to the top and bottom triangular faces of the trigonal prism. Two of the square faces of the prism and a peripheral triangle are bridged by two phosphonates and two methoxide ligands. A lithium ion sits in the cavity of the central trigonal prism. All reported molecular tridecanuclear manganese phosphonate clusters possess a similar type of structural geometry. These contain both homovalent (MnIII) or mixed-valent (MnIIMnIII12) cores. The ligands involved (in addition to phosphonate) are carboxylate or azide. We have synthesized a mixed-valent neutral tridecanuclear MnII12MnIII phosphonate cage, [Mn II Mn III 12 (μ 4 -O) 6 (μ-OH) 6 (O 3 PBu-t) 10 (OH 2 ) 2 (DMF)4]·[2MeOH·4DMF], in the reaction involving of MnCl2 with t-BuPO3H2 without any ancillary ligands or carboxylate ligands (Scheme 53).208 This compound contains a [MnIIMnIII12(μ4-O)6] core whose center is occupied by a MnII ion, which is connected to 12 MnIII ions by six μ-OH−, six μ-O2−, and 10 [t-BuPO3]2− ligands. The vacant coordination sites of six MnIII ions situated in the periphery are occupied by four

Figure 75. Tridecanuclear MnII4MnIII9 core of [MnII4MnIII9O4(OH)2(O3PC10H7)10(C6H5CO2)5(py)8(H2O)6].206 Adapted from ref 206. Copyright 2009 The Royal Society of Chemistry.

Figure 76. A tridecanuclear manganese phosphonate, [MnIIMnIII12(μ 4 -O) 8 (μ 4 -Cl) 6 (t-BuPO 3 ) 8 ][Mn I I CH 3 CN) 6 ]·Cl 2 ·6CH 3 CN· 5.25H2O.209 Adapted from ref 209. Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

DMF and two water molecules. Compounds possessing similar structures, [MnIII13(μ3-O)8(OMe)8(O3PPh)4(O2CCMe3)10],198 and the anionic cages, [n-Bu4N][MnIII13(μ3-O)6(μ-OH)2(μ-N 3 ) 4 (O 3 PBu-t) 1 0 (N 3 ) 2 (HO 2 CMe) 2 (OH 2 ) 2 ] 1 99 and [Mn II Mn III 12 (μ 3 -O) 6 (μ-OH) 6 (O 3 PC 6 H 11 ) 10 (py) 6 ], 180 are known. Another interesting mixed-valent MnII4MnIII9 tridecanuclear cage [Mn II 4 Mn III 9 O 4 (OH) 2 (O 3 PC 10 H 7 ) 10 (C 6 H 5 CO 2 ) 5 (py)8(H2O)6]206 was prepared in the reaction of [Mn3O(O2CC6H5)6(py)2(H2O)] with C10H7PO3H2 in the presence of pyridine. The core of this compound reveals that it is turtleshaped and contains a [Mn2O2] dimer, two [Mn4O2] units, and a [Mn3O4] unit. These are connected to each other by [C10H7PO3]2− and μ3-oxide igands (Figure 75). An interesting mixed-valent tridecanuclear MnIIMnIII12 phosphonate complex, [Mn I I Mn I I I 12 (μ 4 -O) 8 (μ 4 -Cl) 6 (t-BuPO3)8][MnIICH3CN)6]·Cl2·6CH3CN·5.25H2O, was synthesized in the reaction of MnCl2·4H2O, KMnO4, t-BuPO3H2, and AR


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Figure 77. A tetradecanuclear manganese phosphonate, (C5H7N2)[MnII3MnIII11(μ4-O)6(μ3-O)(μ3-OH)(μ2-OH)(μ4-Cl)4(t-BuPO3H)(t-BuPO3)10(2-aminopyridine)·(C5H6N2)·3CH3CN·2H2O.209 Adapted from ref 209. Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 79. An irregular core of [Mn16(Ph2CHPO3)8(μ4-O)6(μ3-O)2(OMe)4(HOMe)2(Me3CCO2)6(OH2)(Py)2].210 Adapted from ref 210. Copyright 2008 American Chemical Society.

Figure 78. Pentadecanuclear core of [Mn 15 O 6 (MePO 3 ) 2 (MeCO2)18(H2O)12][MePO3H]2·12H2O.183 Adapted from ref 183. Copyright 2009 The Royal Society of Chemistry.

Figure 80. Core of the nonadecanuclear manganese phosphonate, [Mn19(μ4-O)6(μ3-O)2(O2CCMe3)10(OCH3)16(O3PPh(Me)2)6].210 Adapted from ref 210. Copyright 2008 American Chemical Society.

NEt3.209 The molecular structure of this complex reveals the presence of three subunits, a central part containing five manganese ions and two planar tetranuclear arrays placed above and below. Apart from the phosphonate ligands, eight (μ4-O) and six (μ4-Cl) assist in stitching the ensemble together. The latter are arranged in the vertices of an octahedron (Figure 76). A mixed-valent tetradecanuclear manganese phosphonate, (C 5 H 7 N 2 )[Mn II 3 Mn III 11 (μ 4 -O) 6 (μ 3 -O)(μ 3 -OH)(μ 2 -OH)(μ 4-Cl)4(t-BuPO3H)(t-BuPO3)10(2-aminopyridine)·(C5H6N2)· 3CH3CN·2H2O, was obtained in the reaction involving MnCl2· 4H2O, KMnO4, t-BuPO3H2, pyridine, and 2-aminopyridine.209 This complex contains three MnII and 11 MnIII ions that are

held together by μ4-O, μ3-O, μ3-OH, μ2-OH, μ4-Cl, [t-BuPO3H]−, and [t-BuPO3]2− ligands (Figure 77). A pentadecanuclear mixed-valent complex, [Mn 15O 6 (MePO3)2(MeCO2)18(H2O)12][MePO3H]2·12H2O, was obtained in a reaction involving Mn(O2CMe)2·4H2O with NBu4MnO4, MePO3H2, and MeCO2H. This compound contains nine MnII and six MnIII ions (Figure 78).183 The 15 manganese centers are connected to each other by six μ4-O and two [MePO3]2− ligands, resulting in a rudder-like core. The two methylphosphonate ligands adopt a 6.222 coordination binding mode. AS


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Figure 81. Molecular structure of the mixed-valent icosanuclear manganese complex, [Et 3NH] 2[MnIII 18 MnII 2(μ4-O)8(μ3-O)4(μ3OH)2(O3PCH2Ph)12(O2CCMe3)10(py)2].181 Adapted from ref 181. Copyright 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 82. A docosanuclear complex, [Mn4IIMn18IIIO12(O3PC6H11)8(O2CCH3)22(H2O)6(py)2].180 Adapted from ref 180. Copyright 2007 American Chemical Society.

The hexadecanuclear manganese complex, [Mn 16 (Ph2CHPO3)8(μ4-O)6(μ3-O)2(OMe)4(HOMe)2(Me3CCO2)6(OH2)(Py)2], contains 10 MnIII and six MnII ions.210 These are arranged in an irregular-shaped cage structure containing a Mn3O triangle and a larger Mn13O7 subunit. These are connected to each other by [Ph2CHPO3]2− and [t-BuCO2]− ligands (Figure 79). The complex [Mn 1 9 (μ 4 -O) 6 (μ 3 -O) 2 (O 2 CCMe 3 ) 1 0 (OCH3)16(O3PPh(Me)2)6] contains nine MnII and 10 MnIII ions (Figure 80).210 The structure of this cage contains a central heptanuclear array with a central manganese in a +2 oxidation state. On either side of this central array is present a tetranuclear motif. Finally, the cage is capped on the top and bottom by two dinuclear units. Within the cage, the oxo ligands stich the manganese ions in the periphery. The phosphonate ligands (along with the carboxylates) support the structure through additional bridging coordination modes.

Reaction of equimolar quantities of PhCH2PO3H2 and [Mn3O(O2CCMe3)6(py)3] in the presence of Et3N afforded [Et3NH]2[MnIII18MnII2(μ4-O)8(μ3-O)4(μ3-OH)2(O3PCH2Ph)12(O2CCMe3)10(py)2].181 This cage has been described as a centrosymmetric cubic-close packed array of manganese centers.181 Twelve of the manganese centers lie in one plane, which includes the two MnII sites. Two MnIII triangles lie above and below the central plane and are bridged to the central layer by a μ4-oxide group. The 12 phosphonate ligands are involved in bridging the various manganese centers through three distinct coordination modes: 3.111, 4.211, and 5.221 (Figure 81). Two other related icosanuclear complexes are K4[MnIII16MnII4(μ4O)4(μ3-O)6(PhCH2PO3)14(PhCO2)12(PhCO2H)0.5(CH3CN)2]181 and Na6[MnIII14MnII6(μ4-O)4(μ3-O)4(OH)4(PhCH2PO3)14(PhCO2)12(PhCO2H)2(H2O)4(CH3CN)4].181 Reaction of [Mn 3 O(O 2 CCH 3 ) 6 (py) 3 ]·ClO 4 with C6H11PO3H2 afforded a mixed-valent docosanuclear complex, [Mn4IIMn18IIIO12(O3PC6H11)8(O2CCH3)22(H2O)6(py)2].180 AT


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Figure 83. Z-shaped MnIII16MnIV2 core of [Mn18(μ3-O)8(PhPO3)14(O2CCMe3)12(py)6(H2O)2].198 Adapted from ref 198. Copyright 2006 WileyVCH Verlag GmbH & Co. KGaA.

Scheme 54. Cluster Expansion Strategy for the Preparation of [Fe4OCl(O2CPh)3(O3PPh)3(py)5],214 [Fe6O(OH)3(O2CMe)3(O3PPh)4(py)9](NO3)2,214 [Fe7O2(O2CPh)9(O3PPh)4(py)6],214 [Fe8O3(OH)2(O2CBu-t)11(PhCH2PO3)3(py)3],215 and [Fe9(μ3-O)4(O3PPh)3(O2CCMe3)13]216

(py)6(H2O)2],198 contains 16 MnIII and two MnIV ions. The Z-shaped core (Figure 83) contains several oxo-centered Mn3O triangular motifs that are connected to each other through bridging phosphonate and pivalate ligands.198

The wheel-like molecule is made up of two equivalent cages: [MnIII9O6(O3PC6H11)2(O2CCH3)8(H2O)]. These are connected to each other by two pairs of MnII2O units by phosphonate and carboxylate ligands (Figure 82). The nonanuclear motif, [MnIII9O6(O3PC6H11)2(O2CCH3)8(H2O)], is comprised of a [MnIII7O4] unit, which itself is formed as a result of the fusion of two butterfly shaped [MnIII4O2] subunits. 10.1.5. MnIII/MnIV. Mixed-valent MnIII/MnIV complexes are sparse. A mixed-valent cage, [Mn18(μ3-O)8(PhPO3)14(O2CCMe3)12-

10.2. Technicium and Rhenium

There are no reports on molecular Tc and Re metal phosphonates. AU


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Scheme 55. Synthesis of a Tetranuclear FeIII Phosphonate, [Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN·5CH2Cl2, Having a D4R Type Core218

Scheme 56. Synthesis of a K2Fe4 Phosphonate, [FeIII4K2(O3PBu-t)2(acac)10]221

Figure 84. Molecular structure of [Fe 4 OCl(O 2 CPh) 3 (O3PPh)3(py)5].214 Adapted from ref 214. Copyright 2003 WileyVCH Verlag GmbH & Co. KGaA.

11. GROUP 8 PHOSPHONATES 11.1. Iron

All of the reported molecular iron phosphonates contain FeIII.214−232 Most of the molecular FeIII phosphonates have been synthesized utilizing the cluster expansion strategy (Scheme 54). Some others have been prepared utilizing iron salts as starting materials. Except for the following six compounds, [Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN·5CH2Cl2,218 [HNEt 3 ] 2 [Fe 5 (μ 3 -O)(μ-OH) 2 (Cl 3 CPO 3 ) 3 (HphpzH) 5 (μphpzH)]·3CH3CN·2H2O(H2phpzH = 3(5)-(2-hydroxyphenyl) pyrazole), 2 1 8 [{Fe 36 (2-pyPO 3 ) 4 4 (H 2 O) 4 8 }]·(ClO 4 ) 2 .1 · (NO3)11.9·(OH)6·47.9H2O·10EtOH (2-pyridylphosphonic acid = 2-pyPO3H),217 [Fe4(2-pyHCH2PO3)4(H2O)12(Cl)(ClO4)7· xH2O] (2-pyCH2PO3 = 2-pyridylmethylphosphonic acid),219 [FeIII4K2(O3PBu-t)2(acac)10]221 (acacH = acetylacetone), and [Fe8Na2(HL)2(H2L)10(H2O)6]·22H2O (H4L = N,N-dimethylaminomethane-1,1-diphosphonic acid),231 which do not contain a Fe3O core, or a carboxylate ligand, all other known molecular FeIII phosphonates contain a Fe3O core as well as carboxylate ligands. The nuclearity of molecular FeIII phosphonates varies from 4 to 36.217 Among the known molecular transition and lanthanide metal phosphonates, the 36 nuclearity of molecular FeIII phosphonate is the largest. All of the known molecular Fe4 systems contain a Fe3O triangular core, except [Fe4(t-BuPO3)4(HphpzH)4] (H2phpzH = 3(5)-(2-hydroxyphenyl)pyrazole)218 and [Fe4(2-pyHCH2PO3)4(H2O)12(Cl)(ClO4)7·xH2O].219 All other reported tetranuclear molecular FeIII phosphonates have been prepared using trinuclear Fe3O carboxylate cages as the starting material (Scheme 53). A representative example is described here. The reaction between [FeIII3O(O2CPh)6(H2O)3]·Cl with PhPO3H2 afforded a tetranuclear oxo-centered triangular core compound, [Fe4OCl(O2CPh)3(O3PPh)3(py)5].214 In this tetranuclear cluster, the bottom layer contains a triangular oxo-centered [Fe3O] units connected with the fourth iron center through O−P−O bridged phosphonate ligand, forming a tetranuclear capped tetrahedron structure. The [PhPO3]2− ligands engage in a 3.111 bridging coordination mode and are involved in

Scheme 57. Synthesis of the Pentanuclear FeIII Phosphonate, [HNEt3]2[Fe5(μ3-O)(μ-OH)2(Cl3CPO3)3(HphpzH)5(μphpzH)]·3CH3CN·2H2O218

bicapping the oxo-centered triangle and fourth iron atom. Each of the FeIII centers in the triangular oxo-core is attached to a single pyridine molecule, while the fourth FeIII center is coordinated to two pyridine molecules (Figure 84).214 An example of a different structural form is provided by [Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN·5CH2Cl2.218 This compound was synthesized in the reaction of Fe(ClO4)2·6H2O with AV


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Figure 87. A heptanuclear FeIII phosphonate complex, [Fe7O2(O2CPh)8(NO3)(O3PPh)4(py)6].214

Figure 85. A hexanuclear FeIII phosphonate, [Fe6O(OH)3(O2CMe)3(O3PPh)4(py)9]·(NO3)2.214 Adapted from ref 214. Copyright 2003 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 88. A mixed-valent heptanuclear iron(III) complex, [Fe7S4(RPO2S)4(DME)4] (piv = t-BuCO2−, R = 4-anisyl, DME = 1,2-dimethoxyethane), containing the [RPO2S]2− ligand.225 Adapted from ref 225. Copyright 2008 The Royal Society of Chemistry.

Figure 86. A peroxide-linked hexanuclear FeIII phosphonate, [Fe6O2(O2)(O2CCMe3)8(O3PPh)2(H2O)2].214 Adapted from ref 214. Copyright 2003 Wiley-VCH Verlag GmbH & Co. KGaA.

Scheme 58. Synthesis of a K2Fe6 Phosphonate, [FeIII6K2(μ3-O)2(μ-OMe)2(O3PBu-t)4(acac)6(OH2)2(MeOH)4]221

Figure 89. Line diagram of [Fe8O3(OH)2(O2CBu-t)11(PhCH2PO3)3(py)3].215

tert-butylphosphonic acid (t-BuPO3H2) in the presence of a chelating nitrogen ligand, 3(5)-(2-hydroxyphenyl)pyrazole [H2phpzH], and NEt3 as the base. The molecular structure reveals that this compound possesses a cubic double-4-ring (D4R) core (Scheme 55). This is similar to other D4R type structures discussed above in the case of other transition and main-group metal ions.35,45,68,70,74,85,88,146,220 The reaction of FeIII(NO3)3·9H2O, t-BuPO3H2, and acacH in the presence of KOMe afforded a heterometallic complex, AW


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Table 15. Molecular Iron Phosphonates reactants Fe(ClO4)2·6H2O, t-BuPO3H2, Et3N, 3(5)-(2-hydroxyphenyl)pyrazole (H2phpzH) [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·Cl, pyridine, PhPO3H2

compounds

218

[Fe4(μ3-O)Cl(PhCO2)3(PhPO3)3(py)5]

tetranuclear/capped tetrahedron -do-do-do-do-do-do-dotetranuclear/cubic pentanuclear

223 223 222 222 224 214 231 228 219 218

hexanuclear -do-do-

214 214 222

-do-do-doheterometallic hexanuclear heptanuclear -do-

223 223 223 221 224 223

-do-do-do-do-do-

223 223 223 214 214

-do-

225

octanuclear -do-

215 221

nonanuclear/icosahedral

3

-do-

225

-do-do-dononanuclear/cyclic nonanuclear/distorted cylindrical nonanuclear/twisted “basket”

216 222 226 227 226 223

-do-do-

223 222

nonanuclear

228

decanuclear

231

-doheterometallic decanuclear

215 77

[Fe6Li5(μ3-O)2(t-BuPO3)6(O2CBu-t)8(MeOH)2(Py)4]

heterometallic undecanuclear

215

[Fe12(μ2-O)4(μ3-O)4(O2CCHPh2)14(4-t-BuPhPO3H)6]

dodecanuclear/double butterfly -doheterometallic dodecanuclear/ Wells−Dawson type core tridecanuclear

226 226 24

tetradecanuclear

214

[Fe4(μ3-O)(t-BuCO2)4(C10H17PO3)3(py)4] [Fe4(O)(O2CCMe3)4(C10H17PO3)3(Py)4](CH3CN)3 [Fe4(O)(O2CPh)4(C10H17PO3)3(Py)4]·(Py)3·(CH3CN)2 [Fe4OCl(O2CMe)3(O3PC6H9)3(py)5] [Fe4OCl(O2CPh)3(O3PPh)3(py)5] [Fe4O(t-BuPO3)3(O2CPh)3(py)3Cl]·3.5py [FeIII4O(O2CBu-t)5(O3PBu-t)3Br] [Fe4(2-PyHCH2PO3)4(H2O)12(Cl)(ClO4)7·xH2O] [HNEt3]2[Fe5(μ3-O)(μ-OH)2 (Cl3CPO3)3(HphpzH)5 (μ-phpzH]·3CH3CN·2H2O [FeIII3O(O2CMe)6(H2O)3]·(NO3), pyridine, PhPO3H2 [Fe6O(OH)3(O2CMe)3(O3PPh)4(py)9]·(NO3)2 [Fe6O2(O2)(O2CCMe3)8(O3PPh)2(H2O)2] [FeIII3O(O2CBu-t)6(H2O)3]·(NO3), pyridine, PhPO3H2 [Fe6O2(O)2(O2CCMe3)8(C10H17PO3)2(H2O)2]· H2O2, C10H17PO3H2, [Fe3O(O2CCMe3)6(H2O)3]·Cl (CH3CN)4 [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), PhPO3H2, pyridine, H2O2 [Fe6(μ3-O)2(O2)(t-BuCO2)8(PhPO3)2(H2O)2] [Fe6(μ3-O)2(O2)(t-BuCO2)8(t-BuPO3)2(py)2] [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), t-BuPO3H2, pyridine, H2O2 [Fe6(μ3-O)2(O2)(t-BuCO2)8(C10H17PO3)2(H2O)2] [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), C10H17PO3H2, pyridine, H2O2 [FeIII4K2(O3PBu-t)2(acac)10] FeIII(NO3)3, t-BuPO3H2, acacH, KOMe [Fe7O2(O2CPh)9(O3PC6H9)4(py)6] [Fe3O(H2O)3(O2CPh)6]·Cl, pyridine, C6H9PO3H2, NEt3 [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·Cl, [Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), [Fe7(μ3-O)2(t-BuPO3)4(t-BuCO2)8(py)8]·(NO3) pyridine, t-BuPO3H2 [Fe3(μ3-O)(MeCO2)6(H2O)3]·Cl, pyridine, PhPO3H2 [Fe7(μ3-O)2(PhPO3)4(MeCO2)9(py)6] [Fe7(μ3-O)2(PhPO3)4(PhCO2)9(py)6] [Fe3(μ3-O)(PhCO2)6(H2O)3]·Cl, pyridine, PhPO3H2 [Fe7(μ3-O)2(PhPO3)4(MeCO2)8(py)8] [Fe3(μ3-O)(MeCO2)6(H2O)3]·Cl, pyridine, PhPO3H2 [Fe7O2(O2CMe)9(O3PPh)4(py)6] [Fe3O(O2CMe)6(H2O)3]·(NO3), pyridine, PhPO3H2 [Fe7O2(O2CPh)9(O3PPh)4(py)6]; [Fe7O2(O2CPh)8(NO3) [FeIII3O(O2CPh)6(H2O)3]·(NO3), pyridine, PhPO3H2 (O3PPh)3(py)6] [Fe3(μ3-O)(μ2-piv)6(H2O)3](piv) (piv = t-BuCO2−), [RP(S)(μ-S)]2 [Fe7S4(RPO2S)4(DME)4] (DME = 1,2-dimethoxyethane) (R = 4-anisyl) (Lawsson’s reagent) [Fe8O3(OH)2(O2CBu-t)11(PhCH2PO3)3(py)3] [Fe3O(piv)6(H2O)3]·Cl, Et3N, pyridine, C6H5CH2PO3H2 [FeIII6K2(μ3-O)2(μ-OMe)2(O3PBu-t)4 FeIII(NO3)3·9H2O, t-BuPO3H2, acacH, KOMe (acac)6(OH2)2(MeOH)4] anhydrous FeCl3, C5H9PO3H2, NEt3, t-BuCO2H [Fe9III(μ3-O)4 (O3PC5H9)3(O2CCMe3)13]·(EtOH)0.5·(Et2O)0.5 [Fe3(μ3-O)(μ2-piv)6(H2O)3]·(piv), (piv = t-BuCO2−), [RP(S)(μ-S)]2 [Fe9(μ3-O)4(RPO3)3(Piv)13] (R = 4-anisyl) [Fe3O(O2CCMe3)(H2O)3](O2CCMe3)·2Me3CCO2H, PhPO3H2, NEt3 [Fe9(μ3-O)4(O3PPh)3(O2CCMe3)13] [Fe9(O)4(O2CBu-t)13(C10H17PO3)3] [Fe3O(O2CBu-t)6(H2O)3]·Cl, t-BuCO2H, NEt3, C10H17PO3H2 [Fe9(μ3-O)4(O3P(Ph(Me)2)3(O2CCMe3)13] [Fe3O(O2CPh)6(H2O)3]·Cl, Et3N, H2O3P(Ph(Me)2) [Fe9(μ-OH)7(μ-O)2(O3PC6H9)8(py)12] [Fe3O(O2CMe)6(H2O)3]·NO3, C6H9PO3H2, pyridine [Fe9(O)3(OH)3(O3PCHPh2)6(O2CBu-t)6(H2O)9] [Fe3O(O2CBu-t)6(H2O)3]·Cl, FeCl3·6H2O, Et3N

[Fe3(μ3-O)(PhCO2)6(H2O)3]·Cl, pyridine, C10H17PO3H2 [Fe3O(O2CPh)6(H2O)3]·Cl, NEt3, C10H17PO3H2 [Fe3O(O2CBu-t)6(H2O)3]·(O2CBu-t), t-BuPO3H2 FeCl3·6H2O, t-BuPO3H2, pyridine [Fe3O(piv)6(pip)3], Et3N, C6H5CH2PO3H2, pip N,N-dimethylaminomethane-1,1-diphosphonic acid (H4L), Fe (NO3)3·9H2O, NaOH pyridine, [Fe3O(O2CBu-t)6(H2O)3]·Cl, LiOMe, t-BuPO3H2, t-BuCO2H, Et3N FeCl3·6H2O, Et3N, [Fe3O(O2CPh)6(H2O)3]·Cl, 4-t-BuPhPO3H2 Et3N, [Fe3O(O2CPh)6(H2O)3]·Cl, C10H17PO3H2 [Fe3(μ3-O)(O2CBu-t)6(HO2CBu-t)3](O2CBu-t), [Ln2(O2CBu-t)6 (HO2CBu-t)6] (Ln = Gd, Tb, Dy, Ho), R = methyl, phenyl, n-hexyl [Fe3O(piv)6(H2O)3]·Cl, t-BuPO3H2, LiOMe, py = pyridine [Fe3O(O2CCMe3)6(H2O)3]·(NO3), pyridine, PhPO3H2

ref

tetranuclear/D4R core

[Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), pyridine, C10H17PO3H FeCl3, NEt3, pyridine, t-BuCO2H, C10H17PO3H2 FeCl3, PhCO2H, NEt3, pyridine, C10H17PO3H2 [Fe3O(O2CMe)6(H2O)3]·Cl, pyridine, C6H9PO3H2, NEt3 [FeIII3O(O2CPh)6(H2O)3]·Cl, pyridine, PhPO3H2 [Fe3(μ3-O)(O2CPh)6(H2O)3]·Cl, t-BuPO3H2, pyridine [Fe3O(O2CBu-t)6(H2O)3]·NO3, FeBr3, t-BuPO3H2 Fe(ClO4)2, PyCH2PO3H2 Fe(ClO4)2·6H2O, Cl3CPO3H2, Et3N, H2phpzH

[Fe3(μ3-O)(t-BuCO2)6(H2O)3]·(NO3), PhPO3H2, pyridine


[Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN·5CH2Cl2

[Fe9(μ3-O)2(μ2-OH)(PhPO3)6(t-BuCO2)10(MeCN) (H2O)5] [Fe9(μ3-O)2(μ2-OH)(C10H17PO3)6(PhCO2)10(H2O)6] [Fe9(O)2(OH) (O2CPh)10(C10H17PO3)6(H2O)2]·(CH3CN)7 [FeIII9(μ3-O)5(μ3-OH)(O2CBu-t)12(HO2CBu-t) (O3PBu-t)2] [Fe10(OH)8(HPO4)(t-BuPO3)8 (t-BuPO3H)4(py)8]·4py·5H2O [Fe10O2(OH)8(O2CBu-t)10(PhCH2PO3)4(pip)2] [Fe8Na2(HL)2(H2L)10(H2O)6]·22H2O

[Fe12(μ2-O)4(μ3-O)4(O2CPh)14(C10H17PO3H)6] [Fe6Ln6(μ3-O)2(CO3)(O3PR)6(O2CBu-t)8] [Et3NH]2[Fe13(μ3-O)3(μ2-OH)7 (t-BuPO3)7(Me3CCO2)14(H2O)] [Fe14O4(O2)2(O2CCMe3)12(O3PPh)8(H2O)12]·(NO3)2 AX

215


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Table 15. continued reactants Fe3O(O2CCMe3)6(H2O)3]·(NO3), pyridine, PhPO3H2, H2O2 [Fe3O(O2CBu-t)6(H2O)3](O2CBu-t), Fe(BF4)2, t-BuPO3H2 2-PyPO3H2, Fe(ClO4)2, Fe(NO3)3 2-PyPO3H2, FeCl3, CF3SO3Ag

compounds [Fe14(μ3-O)4(O2)2(PhPO3)8(t-BuCO2)12(H2O)12]·(NO3)2 [FeIII14(μ3-O)4(μ-OH)8(O2CBu-t)14(O3PBu-t)6] [{Fe36(2-PyPO3)44(H2O)48}]·(ClO4)2.1(NO3)11.9(OH)6· 47·9H2O·10EtOH [Fe36(2-PyPO3)44(H2O)48]·(OH)6(CF3SO3)14·2EtOH· 72H2O

[FeIII4K2(O3PBu-t)2(acac)10].221 The latter contains four FeIII and two KI ions that are held together by two bridging [t-BuPO3]2− and 10 [acac]− ligands (Scheme 56). The central core of this compound consists of two {FeIII(acac)2} units that are bridged by two [t-BuPO3]2− ligands in a 2.110 coordination binding mode. Two potassium ions are linked through the other two terminal units of {FeIII(acac)3}.221 Only one pentanuclear FeIII phosphonate, [HNEt3]2[Fe5(μ3-O)(μ-OH) 2 (Cl 3 CPO 3 ) 3 (HphpzH) 5 (μ-phpzH)]·3CH 3 CN· 2H 2 O, 2 1 8 is known, which was obtained in the reaction of Fe(ClO 4 ) 2 ·6H 2 O with trichloromethylphosphonic acid (Cl 3 CPO 3 H 2 ) and 3(5)-(2-hydroxyphenyl)pyrazole [H2phpzH] (Scheme 57).218 The pentanuclear FeIII cage is assembled through the multiple coordination action of μ3-O, μOH, [Cl3CPO3]2−, [HphpzH]−, and [phpzH]2− ligands. Interestingly, this cage possesses both Fe3O and Fe2(OH) motifs. A μ3-O ligand assists the formation of a trinuclear oxocentered Fe3O core, while the μ-OH forms a dinuclear Fe2(OH) core structure. Both the phenolate oxygen and the pyrazolyl nitrogen of [HphpzH]− and [phpzH]2− ligands are involved in bridging coordination modes. Each iron center is bound by the chelating coordination action of the ancillary ligand (N∧O).218 Among the hexanuclear molecular FeIII phosphonates known so far, three types of structural geometry are present. Except one example, [FeIII6K2(μ3-O)2(μ-OMe)2(O3PBu-t)4(acac)6(OH2)2(MeOH)4],221 all other hexanuclear FeIII phosphonate clusters were prepared by the cluster expansion strategy utilizing Fe3O oxo-centered triangular carboxylate cages as starting materials.214,222,223 All of them possess μ3-O ligands. In addition, some of them contain μ3-O, μ-OH/μ-OMe, or μ3-O and peroxide (−O−O−) ligands. [Fe6O(OH)3(O2CMe)3(O3PPh)4(py)9]·(NO3)2 contains both Fe3O and Fe2(OH) motifs and has been synthesized in the reaction of the triangular Fe3O carboxylate cage,214 [Fe3O(O2CMe)6(H2O)3]·(NO3) with PhPO3H2 in the presence of pyridine (Figure 85). This cage consists of two iron triangles connected to each other by the [PhPO3]2− ligands (3.111 coordination). One of the triangular motifs contains a Fe3O unit; alternate iron centers are linked to each other by three carboxylates ligands. In the other triangle, three pairs of iron centers are connected to each other through a μ-OH ligand.214 The reaction of [Fe3O(O2CMe)6(H2O)3]·(NO3) with PhPO3H2 in the presence hydrogen peroxide afforded a symmetrical, peroxide-containing, hexanuclear FeIII phosphonate cage, [Fe6O2(O2)(O2CCMe3)8(O3PPh)2(H2O)2].214 Two oxo-centered FeIII triangles are connected to each other by the multiple bridging coordination action of two [PhPO3]2− (4.211 mode), a peroxide (−O−O−) [4.22 mode], and two (Me3CCO2)− (2.11 mode) ligands resulting in a “butterfly” like Fe6(O2)(O)2 motif (Figure 86). An interesting aspect of the structure is that the phosphorus atoms and the peroxide ligand lie on a crystallographic mirror plane.


ref

-do-dohexatriaconta-nuclearity

223 228 217

-do-

217

Scheme 59. Synthesis of Nonanuclear Iron(III) Phosphonate Complexes by Utilizing the Cluster Expansion Strategy216,222,225−228

The hexanuclear FeIII phosphonate cage, [FeIII6K2(μ3-O)2(μ-OMe)2(O3PBu-t)4(acac)6(OH2)2(MeOH)4] (acacH = acetylacetone), was synthesized in the reaction involving FeIII(NO3)3· 9H2O, t-BuPO3H2, acacH, and KOMe (Scheme 58).221 This cage consists of six FeIII and two KI ions, which are held together by two μ3-O, two μ-OMe, and four [t-BuPO3]2− ligands. In addition, out of six FeIII centers, five FeIII ions are bonded with acetylacetonate ligands. The bottom of this structure is built up of a vertex-shared bitriangle unit [{FeIII5(μ3-O)2(μ-OMe)2}] while two KI ions are present in the middle. An isolated FeIII ion is present at the top. The vertex-shared bitriangular {FeIII5(μ3-O)2(μ-OMe)2} unit consists of two oxo-centered triangles of {FeIII3(μ3-O)} subunits. The two FeIII atoms in each outside edge of the bitriangle are bridged by a methoxy group, and the two opposite edges contain one [t-BuPO3]2− ligand that binds in a 3.111 coordination mode. The two iron motifs are linked through bridging [t-BuPO3]2− ligands. In addition, this cage contains four MeOH molecules coordinated to the potassium ions and two water molecules bound to vertex centered FeIII ions.221 AY


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Scheme 60. Synthesis of the Nonanuclear FeIII Phosphonate Cage, [Fe9III(μ3-O)4(O3PC5H9)3(O2CCMe3)13]3

Figure 90. A cyclic nonanuclear FeIII phosphonate, [Fe9(μ-OH)7(μO)2(O3PC6H9)8(py)12].227 Adapted from ref 227. Copyright 2006 The Royal Society of Chemistry.

All of the heptanuclear molecular FeIII phosphonates possess an isostructural core. 214,223,224 Reaction of [Fe III 3 O(O2CPh)6(H2O)3]·(NO3) with PhPO3H2 in the presence of pyridine afforded a heptanuclear FeIII phosphnate cage, [Fe7O2(O2CPh)8(NO3)(O3PPh)4(py)6].214 This cage contains two identical Fe3O triangular units that are fused to each other by a central FeIII center via two bridging [PhPO3]2− ligands (Figure 87). In each of the triangular Fe3O motifs, two pairs of iron centers are bridged by carboxylate ligands; the third iron center is linked to the central iron through the [PhPO3]2− ligand. Although slightly unrelated, mention must be made of the heptanuclear mixed-valent complex [Fe7S4(RPO2S)4(DME)4] (piv = t-BuCO2-, R = 4-anisyl, DME = 1,2-dimethoxyethane)225 shown in Figure 88, which contains the ligand [RPO2S]2−. The latter is closely related to the phosphonate family of ligands. This compound was synthesized by partial P−S bond cleavage of Lawsson’s reagent, [RP(S)(μ-S)]2 (R = 4-anisyl), when it was reacted with [Fe3(μ3-O)(μ2-piv)6(H2O)3](piv) (piv = t-BuCO2−). The iron atoms are in the vertices of an octahedron; free sulfide and [RPO2S]2− ligands assist in holding the cage together. These systems need to be explored more considering the scarcity of compounds containing [RPO2S]2− ligands.225 The octanuclear complex, [Fe 8 O 3 (OH) 2 (O 2 CBut)11(PhCH2PO3)3(py)3],215 was obtained in the reaction of [Fe3O(piv)6(H2O)3]·Cl and PhCH2PO3H2 in the presence of nitrogenous bases. Two distinct structural subunits containing trinuclear and pentanuclear motifs are attached to each other by a [PhCH2PO3]2− and a [OH]− ligand (Figure 89). Both of these units contain the ubiquitous triangular Fe3O units. Nonanuclear FeIII phosphonate clusters possess several types of structural motifs: diminished icosahedral,3,216,222,225,226 cyclic, 227 distorted cylindrical, 226 and twisted basketlike222,223,228 geometries. Except [Fe9III(μ3-O)4(O3PC5H9)3(O2CCMe3)13],3 all other nonanuclear FeIII phosphonates were synthesized utilizing the cluster expansion strategy

Figure 91. A distorted cylindrical core of the nonanuclear complex, [Fe9(μ3-O)3(μ2-OH)3(O3PCHPh2)6(O2CCMe3)6].226 Adapted from ref 226. Copyright 2008 American Chemical Society.

(see Table 15 and Scheme 59). Representative examples of nonanuclear FeIII phosphonates are discussed below. [Fe9III(μ3-O)4(O3PC5H9)3(O2CCMe3)13] was obtained in a direct three-component reaction of anhydrous ferric chloride, cyclopentylphosphonic acid, and pivalic acid in the presence of triethylamine as the base (Scheme 60). The nonanuclear cage possesses a distorted icosahedral core structure where nine of the icosahedral vertices are occupied by FeIII atoms and the remaining three vertices are occupied by the phosphorus atoms of the cyclopentylphosphonate ligand. The cage is built through the multiple coordination action of three [C5H9PO3]2−, 13 [t-BuCO2]−, and four [μ3-O] ligands.3 An interesting cyclic nonanuclear FeIII phosphonate cage, [Fe9(μ-OH)7(μ-O)2(O3PC6H9)8(py)12] (Figure 90)227 has AZ


Chemical Reviews

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Figure 95. Decanuclear FeIII phosphonate, [Fe10(OH)8(HPO4) (t-BuPO3)8(t-BuPO3H)4(py)8]·4py·5H2O, containing also the phosphate ligand, HPO4.231 Adapted from ref 231. Copyright 2009 American Chemical Society.

Figure 92. Twisted basket-like core of [Fe9(O)2(OH)(O2CPh)10(C10H17PO3)6(H2O)2]·(CH3CN)7.222 Adapted from ref 222. Copyright 2006 American Chemical Society.

Figure 96. Dodecanuclear core of [Fe 1 2 (μ 2 -O) 4 (μ 3 -O) 4 (O2CCHPh2)14(4-t-BuPhPO3H)6].226 Adapted from ref 226. Copyright 2008 American Chemical Society.

Figure 93. Nonanuclear core of [FeIII9(μ3-O)5(μ3-OH)(O2CBu-t)12(HO2CBu-t)(O3PBu-t)2].228 Adapted from ref 228. Copyright 2012 Springer Science.

Figure 97. Tridecanuclear core of [Et3NH]2[Fe13(μ3-O)3(μ2-OH)7(t-BuPO3)7(Me3CCO2)14(H2O)].215 Adapted from ref 215. Copyright 2009 The Royal Society of Chemistry.

been synthesized in the reaction of [Fe3O(O2CMe)6(H2O)3]· NO3 with C6H9PO3H2 using pyridine as the base. All of the FeIII atoms are connected to each other through μ-O and μ-OH

Figure 94. A decametallic FeIII phosphonate, [Fe10O2(HO)8(O2CBu-t)10(PhCH2PO3)4(pip)2] [pip = piperidine].215 Adapted from ref 215. Copyright 2009 The Royal Society of Chemistry. BA


Chemical Reviews

Review

Figure 98. Core of a tetradecanuclear FeIII phosphonate, [Fe14O4(O2)2(O2CCMe3)12(O3PPh)8(H2O)12]·(NO3)2.214,223 Adapted from ref 223. Copyright 2009 American Chemical Society.

Figure 99. Rugby ball-shaped core of [FeIII14(μ3-O)4(μ-OH)8(O2CBu-t)14(O3PBu-t)6].228 Adapted from ref 228. Copyright 2012 Springer Science.

Figure 101. Wells−Dawson core of the heterometallic dodecanuclear core of [Fe6Gd6(μ3-O)2(CO3)(O3PR)6(O2CBu-t)8].24 Adapted from ref 24. Copyright 2014 American Chemical Society.

Figure 100. A Fe36 phosphonate, [{Fe36(2-PyPO3)44(H2O)48}]· (ClO4)2.1(NO3)11.9(OH)6·47·9H2O·10EtOH.217 Adapted from ref 217. Copyright 2013 American Chemical Society.

A nonanuclear distorted cylindrical core is the structural motif of [Fe9(μ3-O)3(μ2-OH)3 (O3PCHPh2)6(O2CCMe3)6] (Figure 91).226 This cage contains three layers, and each of the layers contains the ubiquitous Fe3O triangles. Two terminal

ligands, forming an 18-membered ring, [Fe9(μ-O)2(μ-OH)7]. Five [C6H9PO3]2− ligands are involved in the cage formation, each of which cap three iron centers.227 BB


Chemical Reviews

Review

Table 16. Molecular Ruthenium Phosphonates reactants

compounds

[Ru2(μ-O2CCH3)4(O2CCH3)2]H·0.7H2O, HPhPO2H/PhPO3H2 (NH4)3[Ru2(hedp)2]·2H2O/Na4[Ru2(hedp)2Cl]·16H2O, 35% peracetic acid, pip RuCl3·xH2O, hedpH4·H2O [hedpH4 = 1-hydroxyethylidenediphosphonic acid], NH3·H2O, hydrothermal, 140 °C, 6.5 days (NH4)3[Ru2(hedp)2]·2H2O, aqueous KCl

symmetrical Fe3O triangles are linked to the central Fe3O triangle through the bridging coordination action of [Ph2CHPO3]2− ligands. The middle layer contains three FeIII atoms that are connected to each other by three μ2-OH and one μ3-O ligands. The terminal triangles are connected to the central triangle through the [Ph2CHPO3]2− ligands. The carboxylate ligands are involved in holding the terminal triangles (Figure 91). The reaction of [Fe3O(O2CPh)6(H2O)3]·Cl with C10H17PO3H2 [C10H17PO3H2 = camphyl phosphonic acid] afforded [Fe9(O)2(OH)(O2CPh)10(C10H17PO3H2)6(H2O)2]· (CH3CN)7, which possesses an interesting twisted basket-like core structure (Figure 92).222 The latter contains two oxocentered iron triangles, which are fused by a Fe−(OH)−Fe subunit. These three subunits are finally connected to a single FeIII site through the multiple bridging coordination action of [C10H17PO3]2− ligands. Two edges of each triangular core are connected by the [PhCO2]− ligands, while the remaining edge is bridged with Fe−(OH)−Fe unit through [C10H17PO3]2− and [PhCO2]− ligands resulting in the twisted “basket”-like core (Figure 92). The last structural motif among the nonanuclear FeIII phosphonate cages is displayed in [FeIII9(μ3-O)5(μ3-OH)(O2CBu-t)12(HO2CBu-t)(O3PBu-t)2].228 The core of this compound contains three layers: the bottom layer contains two Fe3O triangles that are linked through [t-BuPO3]2− and [t-BuCO2]− ligands. The central layer contains four iron atoms, which are connected to each other by [t-BuPO3]2−, [t-BuCO2]−, and μ3-O ligands, while the top layer consists of two iron atoms that are connected to the central layer by μ3OH, [t-BuPO3]2−, and [t-BuCO2]− ligands. In the top layer, [tBuCO2]− ligands are involved in bridging two iron centers. In this compound, the two [t-BuPO3]2− ligands bind to five iron centers in a 5.221 coordination binding mode (Figure 93).228 The reaction of [Fe3O(piv)6(pip)3] with C6H5CH2PO3H2 in the presence of Et3N afforded a decametallic FeIII phosphonate complex [Fe 10 O 2 (HO) 8 (O 2 CBu-t) 10 (PhCH 2 PO 3 ) 4 (pip) 2 ] [pip = piperidine] (Figure 94).215 This complex contains a [FeIII10(μ3-O)2(μ3-OH)4(μ2-OH)4] core, which is described as containing four edge-sharing {Fe3(μ3-OH)} triangles and two central {Fe4(μ3-OH)2} butterfly shaped units linked to two terminal {Fe3(μ3-O)} triangles. The peripheral sites of this cage are occupied by 10 [Me3CCO2]− and four [PhCH2PO3]2− ligands. A similar type of a double-butterfly structural motif has been observed in [Fe 8 (μ 3 -O) 2 (μ 4 -O) 2 (μ-OCH 2 But)2(μ-O2CC6H5)12(O2CC6H5)2(HOCH2Bu-t)2]·4toluene.229 Interestingly, two iron decanuclear cages, [Fe10O4(OH)2(HL)2(O2CCMe3)12(H2O)2]230 and [NaFe10O3(OH)4(HL)2(O2CCMe3)13]230 (HL = 2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol), with stacked butterfly like core structures similar to [Fe10O2(HO)8(O2CBut)10(PhCH2PO3)4(pip)2] are known.215


ref

[Ru2(μ-O2CCH3)4(HPhPO2)2]H, [Ru2(μ-O2CCH3)4(PhPO3H)2]H·H2O (H2pip)2[Ru2(hedp)2Cl2]·6H2O; (H2pip)2[Ru2(hedp)2(H2O)Cl]·5H2O [(NH4)3Ru2(hedp)2]·2H2O

dinuclear/paddle wheel shaped -do-

232

-do-

234

K3[Ru2(hedp)2(H2O)2]·6H2O

-do-

235

233

The decanuclear complex, [Fe10(OH)8(HPO4)(t-BuPO3)8(t-BuPO3H)4(py)8]·4py·5H2O, was isolated in the reaction of FeCl3·6H2O with t-BuPO3H2 in the presence of pyridine.231 This compound contains 10 iron(III) atoms that are held together by one [HPO 4 ] 3− , eight [t-BuPO 3 ] 2− , four [t-BuPO3H]−, eight μ-OH, and eight pyridine ligands. This cage contains a central [HPO4]3− ligand holding the 10 FeIII atoms, which contains two 12-membered Fe5(μ-OH)4(PO2) rings, each consisting of five FeIII ions and four μ-OH ligands (Figure 95). The reaction of FeCl3·6H2O and 4-t-BuPhPO3H2 in the presence of Et3N afforded a dodecanuclear FeIII phosphonate cage, [Fe 1 2 (μ 2 -O) 4 (μ 3 -O) 4 (O 2 CCHPh 2 ) 1 4 (4-t-BuPhPO3H)6].226 The structure of this compound contains two symmetry related Fe6 units that are held together by the bridging coordination action of [Ph2CHCO2]−, [4-t-BuPhPO3H]−, μ2-O, and μ3-O ligands. Each Fe6 unit consists of two Fe3O triangles (Figure 96); the central eight FeIII atoms are connected to each other by μ2-O, [Ph2CHCO2]−, and [4-tBuPhPO3H]− ligands.226 An interesting tridecanuclear FeIII phosphonate cage, [Et 3 NH] 2 [Fe 13 (μ 3 -O) 3 (μ 2 -OH) 7 (t-BuPO 3 ) 7 (Me 3 CCO 2 ) 14 (H2O)] (Figure 97),215 was synthesized in the reaction of [Fe3O(piv)6(H2O)3]·Cl, t-BuPO3H2, LiOMe, and pyridine. This cage contains three types of structural motifs, a triangle, a cube, and a dinuclear unit. The distorted cubic subunit contains eight FeIII centers that are connected to each other by μ-OH, [t-BuPO3]2−, and [Me3CCO2]− ligands. The top and bottom parts of the distorted cube are capped by [t-BuPO3]2− ligands. This subunit is connected on one side to a Fe3O triangular core and on the other to a Fe2 subunit through [t-BuPO3]2− ligands.215 Two types of tetradecanuclear FeIII phosphonate complexes are known.214,223,228 One of these, containing two peroxide ligands, [Fe 14 O 4 (O 2 ) 2 (O 2 CCMe 3 ) 12 (O 3 PPh) 8 (H 2 O) 12 ]· (NO3)2,214,223 has been synthesized in the reaction of [Fe3O(O2CCMe3)6(H2O)3]·(NO3), PhPO3H2, and pyridine. The molecular structure of this complex consists of two hexameric units, each of which is composed of two Fe3O triangles (Figure 98). The two hexamers are linked to two central iron centers. In this case, also the phosphonate ligands not only assist in holding the subunits but also in stitching the various subunits to form the whole cage. Another tetradecnuclear complex, [FeIII14(μ3-O)4(μ-OH)8(O2CBu-t)14(O3PBu-t)6],228 prepared in the reaction of [Fe 3 O(O 2 CBu-t) 6 (H 2 O) 3 ]·(O 2 CBu-t), Fe(BF 4 ) 2 , and t-BuPO3H2 possesses a rugby-shaped core (Figure 99). The latter contains two identical [Fe7] subunits that are bridged to each other by four [t-BuPO3]2− ligands. Each of the [Fe7] subunits consists of two Fe3O triangles connected to a single central iron(III) site. While the triangles are held together by the phosphonate ligands, the central iron is connected to the triangles by the μ-OH ligands. BC


Chemical Reviews

Review

Figure 104. A trinuclear osmium phosphinate complex, (μ-H)2Os3(CO)10(μ,η2-O2PPh2).236 Adapted from ref 236. Copyright 1992 Elsevier Masson SAS.

Figure 102. Dinuclear ruthenium complexes, (a) [Ru 2 (μO2CCH3)4(HPhPO2)2]H and (b) [Ru2(μ-O2CCH3)4(PhPO3H)2]H· H2O, containing terminal phosphonate ligands.232 Adapted from ref 232. Copyright 1993 Elsevier Masson SAS.

Figure 105. A mononuclear CoII phosphonate, [Co(bipy)(hedpH3)2]· H2O.243 Adapted from ref 243. Copyright 2013 The Royal Society of Chemistry.

coordinated iron centers that are connected to each other by the multiple coordination action of the phosphonate ligands (Figure 100). All molecular FeIII phosphonates are summarized in Table 15.214−232 In addition to the homometallic compounds described above, recently Winpenny et al. synthesized heterometallic dodecanuclear complexes, [Fe 6Ln6(μ3-O)2(CO3)(O3PR)6(O2CBu-t) 8], where R = methyl, phenyl, or n-hexyl and Ln = Gd, Tb, Dy, or Ho.24 These complexes have been prepared by utilizing the cluster expansion strategy involving the reaction of [Fe 3 (μ 3 -O)(O 2 CBu-t) 6 (HO 2 CBu-t) 3 ]·(O 2 CBu-t) and [Ln2(O2CBu-t)6(HO2CBu-t)6] (Ln = Gd, Tb, Dy, or Ho). These complexes possess the so-called Wells−Dawson type Fe6Ln6 core, as shown in Figure 101. The inner part of the core contains six FeIII ions, while the outer part is occupied by six GdIII ions. Both the inner and the outer parts are connected to each other by bridging [RPO3]2− and [t-BuCO2]− ligands.24

Figure 103. A paddle wheel-shaped diruthenium complex, (H2pip)2[Ru2(hedp)2Cl2]·6H2O.233 Adapted from ref 233. Copyright 2013 The Royal Society of Chemistry.

Recently, Dunbar et al. prepared the highest nuclearity transition metal FeIII molecular phosphonates, [{Fe36(2PyPO 3 ) 44 (H 2 O) 48 }]·(ClO 4 ) 2.1 (NO 3 ) 11.9 (OH) 6 ·47·9H 2 O· 10EtOH and [Fe36(2-PyPO3)44(H2O)48]·(OH)6(CF3SO3)14· 2EtOH·72H2O, in the reaction of 2-pyridylphosphonic acid (2-PyPO3H2) and Fe(ClO4)2/Fe(NO3)3/FeCl3 metal salts.217 This cage contains a dual-shell arrangement of 36 octahedrally BD


BE

-do-do-do-do-do-dooctanuclear -do-dononanuclear/30membered macrocycle nonanuclear -doheterometallic nonanuclear decanuclear/planar

[Co2(SbAr)4O4(O3PPh)4(OMe)4(3-picoline)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(4-picoline)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(C9H7N)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(C3H4N2)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(C11H9N)2] [Co2(SbAr)4O4(O3PPh)4(OMe)4(MeOH)2] [Et3NH][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2] [HNEt3][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2] [Co4Cr4(μ3-OH)4(O3PBu-t)2(O2CBu-t)6 (μ-OEt)4(OEt)2(HO2CBu-t)4]·(EtOH)0.8

[t-BuPO3Co(2-apy)]4 (H3O)6·[Co4(H2O)4(HPMIDA)2(PMIDA)2)]·2H2O [Co2V2O2(PMIDA)2(H2O)10]·2(H2O) [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2] [Co2(SbAr)2(O3PBu-t)3O2(OMe)2(py)2] [Co6(chp)8(O3PBu-t)2(Hchp)2(H2O)2] [Co6(chp)6(Hchp)2(O3PBu-t)(O2CPh-2-Ph)3(F)(H2O)·(HNEt3)·(Cl) [CoII4GdIII2(O3PBu-t)2(O2CBu-t)10(MeCN)2]·(MeCN)2

[Co9(3,5-Me2Pz)12(3,5-Me2PzH)6(Cl3CPO3)3]·(toluene)7 [Co9(chp)9(O3PBu-t)(O2CBu-t)6(OH)] [Co9(chp)7(O3PCH2Ph)3(O2CCPh3)5(OH)(H2O)2(MeCN)] [Co4(SbAr)5O9(O3PPh)6(py)4] [Co10{2,3,5,6-(Me)4- C6HCH2PO3}8{2,3,5,6-(Me)4C6HCH2PO3H}4Cl6]·6Et3NH·10nhexane·16H2O [Co10(OH)2(chp)14(O3PCH2CH2PO3)] [Co10(chp)12(O3PPh)2(O2CPh)4 (H2O)4] [Co10(chp)12(O3PPh)2(O2CBu-t)4 (H2O)4] [Co10(chp)12(O3PPh)2(O2C−C6H4-4-Bu-t)4(H2O)4] [Co10(chp)12(O3PPh)2(O2CPh-2-Ph)4(H2O)4]

2-aminopyridine (2-apy), t-BuPO3H2, Co(OAc)2·4H2O N-(phosphonomethyl)iminodiacetic acid (H4PMIDA), CoCl2·6H2O, NH4F, Me4NOH H4PMIDA, VOSO4·5H2O, Co(CH3CO2)2·4H2O, NaOH

[(SbAr)4O2(t-BuPO3H)4(t-BuPO3)4], LiOMe, pyridine, Co(OAc)2·4H2O ArSbO3H2, t-BuPO3H2, LiOMe/pyridine, Co(OAc)2·4H2O Hchp, Co(NO3)2·6H2O, t-BuPO3H2 Co(BF4)2·6H2O, Hchp, NEt3, t-BuPO3H2, 2-biphenylcarboxylic acid [CoII2(μ-OH2) (O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], t-BuPO3H2, Et3N [(SbAr)4O2(PhPO3H)4(PhPO3)4], 3-picoline, Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 4-picoline, Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], quinoline (C9H7N), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 1,2-diazole (C3H4N2), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], 4-phenylpyridine (C11H9N), Co(OAc)2·4H2O [(SbAr)4O2(PhPO3H)4(PhPO3)4], LiOMe, pyridine, Co(OAc)2·4H2O Co(NO3)2·6H2O, PhPO3H2, Hchp, NEt3 Hchp, Co(ClO4)2·6H2O, Co(NO3)2·6H2O, PhPO3H2 t-BuPO3H2, [Cr3(μ3-O)(O2CBu-t)6(H2O)3]·(O2CBu-t), [Co2(μ-OH2) (O2CBu-t)4(HO2CBu-t)4] Co(ClO4)2·6H2O, CCl3PO3H2, 3,5-Me2PzH, NEt3

Co(BF4)2·6H2O, Hchp, NEt3, t-BuPO3H2, t-BuCO2H Co(BF4)2·6H2O, Hchp, NEt3, HO2CCPh3(HO3PCH2Ph), PhCH2PO3H2 [(SbAr)4O2(PhPO3H)4(PhPO3)4], pyridine, Co(OAc)2·4H2O

2,3,5,6-Me4C6HCH2PO3H2, Et3N, anhydrous CoCl2

Hchp, Co(ClO4)2·6H2O, H2PO3CH2CH2PO3H2, Co(BF4)2·6H2O Co(BF4)2·6H2O, PhPO3H2, Hchp, NEt3, PhCO2H Co(BF4)2·6H2O, PhPO3H2, Hchp, NEt3, t-BuCO2H Co(BF4)2·6H2O, PhPO3H2, Hchp, NEt3, 4-tert-butylbenzoic acid Co(BF4)2·6H2O, PhPO3H2, Hchp, NEt3, HO2CPh-2-Ph

[HNEt3]2[Co2(η -3,5-Me2PzH)2Cl2(Cl3CPO3)2] [Co2{Cl2C(PO3)2}(H2O)7·4H2O] [Co4(Ph3CPO3)4(py)4]

decanuclear -do-do-do-do-

dinuclear/cyclic eightmembered ring -do-dotetranuclear/D4R subunit -dotetranuclear heterometallic/ tetranuclear -do-dohexanuclear -do-do-

1

[{Co2(η1-3,5-Me2PzH)4(Cl3CPO3)2}{Co(η1-3,5-Me2PzH)2Cl2}2]·(toluene)2

nuclearity/structure mononuclear -do-do-do-do-

compounds [Co(bipy)(hedpH3)2]·H2O [Co(phen)(hedpH3)2]·H2O [Co(hedpH2)3]·3NH2(CH3)2·NH(CH3)3·3H2O [Co{N(CH2PO3H)2(CH2CO2H)}(H2O)2]·2H2O [Co(Pam)2(H2O)2]·3H2O

CoCl2, CCl3PO3H2, 3,5-Me2PzH, NEt3 Cl2C(PO3H2)2, Co(NO3)2·6H2O Ph3CPO3H2, Co(OAc)2·6H2O, pyridine

CoCl2·6H2O, bipy, 1-hydroxyethylidene-diphosphonic acid (hedpH4) CoCl2·6H2O, phen, hedpH4 Co(Ac)2·4H2O, hedpH4 N,N-bis(phosphonomethyl)glycine [N(CH2PO3H2)2(CH2CO2H)], Co(NO3)2·6H2O sodium pamidronate (3-amino-1-hydroxypropane-1,1-diylphosphonic acid sodium salt (NaPam), CoCl2·6H2O CoCl2, CCl3PO3H2, 3,5-Me2PzH, NEt3

reactants

Table 17. Molecular Cobalt Phosphonates ref

237 242 242 242 242

247

242 242 120

246

120 120 120 120 120 120 240 237 170

120 117 237 242 1

220 245 252

244 251 45

244

243 243 211 249 250



BF


-dotridecanuclear -do-do-dotetradecanuclear -do-do-doheterometallic tetradecanuclear -do-do-do-dopentadecanuclear -do-do-

[Co13(OH)3(chp)19(O3PPh)2(H2O)2(EtOAc)2]; [Co13(OH)3(chp)19(O3PPh)2(H2O)2(Hchp)2] [Co13(OH)3(chp)19(O3PPh)2(H2O)2(EtOAc)2] Na[Co12(PMAS)6(H2O)17(OH)]·xH2O Na8[CoMo4O12(hedp)2]·18H2O [Co14(OH)4(chp)20(O3PCH2Ph)2(H2O)2] [Co14(OH)2(F)2(chp)20(O3PMe)2] [Co14(OH)2(F)2(chp)20(O3PEt)2(H2O)2 [Co14(OH)2(F)2(chp)20{O3P(CH2)7CH3}2(H2O)2] [CoII6LnIII8(μ3-OH)8(O3PBu-t)6(O2CBu-t)16(H2O)2(MeCN)x](MeCN)y (for x = 0 and y = 2, Ln = Gd, Tb, Dy, Ho, for x = 2 and y = 1, Ln = Er, Yb) [CoII6YIII8(μ3-OH)8(O3PBu-t)6(O2CBu-t)16(H2O)2(MeCN)x] (MeCN)y (x = 2 and y =1) [Co4Ln10(O2CBu-t)12 (O3PC6H10NH2)8(PO4)2(O2CMe)2(O3PC6H10NH3)2] (Ln = Gd, Dy) [Co6Na8(chp)12(O3PPh)4(MeCN)4] [Co6Na8(chp)12(O3PPh)4(MeCN)4] [Co15(chp)8(Hchp)(O3PR)8(O2CBu-t)6(CH3CN)3]·(CH3CN) (R = 3-chlorobenzyl) [Co15L6(H2O)24][trans-E]3·xH2O [Co15(chp)8(chpH)(O3PR)8(O2CBu-t)6(CH3CN)3]·(CH3CN), [R = p-nitrobenzyl]

-doundecanuclear -dododecanuclear -do-do-doheterometallic dodecanuclear -do-

-do-do-do-do-do-do-do-doheterometallic decanuclear -do-

[CoII8GdIII4(O3PBu-t)6(O2CBu-t)16]

[CoII8GdIII4(O3PBu-t)6(O2CBu-t)16]

[CoII4LnIII6(O3PCH2Ph)6(O2CBu-t)14(HO2CBu-t)x(MeCN)y(H2O)z] (x = z = 0 and y = 2, Ln = Gd, Tb; x = 1, y = 1, and z = 2, Ln = Dy, Y) [CoII4GdIII6(O3PCH2Ph)6(O2CBu-t)14(MeCN)2] [Co11(OH)(chp)18(FPO3)] [(μ-HPiv)2(μ2-Hmhp)4Na6Co5(μ6,η2-O3PPh)2(μ3,η2-Piv)2(μ3-Piv)3(μ-Piv)7]2·(C10H22) [Co12(chp)15(O3PBu-t)(F)3(OH)4] [Co12(chpH)2(O3PR)4(O2CBu-t)12(CO3)4]·(CH3CN), R= p-nitrobenzyl [Co12(μ3-OH)4(HCO3)6(O3PR)4(O2CBu-t)6(HO2CBu-t)6] (R = p-tert-butylphenyl) [Co12(OH)2(chp)18(O3PCH2Nap)(HBO3)(H2O)] [Co8Cr4(μ3-OMe)2(O3PBu-t)4(O2CBu-t)8(μ-OMe)10(HOMe)6]·(MeOH)1.6

[CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Ln2(O2CBu-t)6 (HO2CBu-t)6] (Ln = Gd, Tb, Dy, Y), Et3N, NaOMe, NaOEt, KOH, H2O3PCH2Ph [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2 Co(BF4)2·6H2O, FPO3H2, Hchp, NEt3 6-methyl-2-pyridone (Hmhp), {Co(Piv)2}n, Na2O3PPh, NaPiv Co(NO3)2·6H2O, Co(BF4)2·6H2O, Hchp, NaOMe, t-BuPO3H2 [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, Hchp, p-NO2C6H4PO3H2 [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4], Et3N, p-tert-butylphenyl phosphonic acid NapCH2PO3H2, Co(BF4)2·6H2O t-BuPO3H2, [Cr3(μ3-O)(O2CBu-t)6(H2O)3]·(O2CBu-t), [Co2(μ-OH2) (O2CBu-t)4(HO2CBu-t)4] [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], t-BuPO3H2, Et3N [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], t-BuPO3H2, Et3N PhPO3H2, Co(OH)2, Hchp Co(NO3)2·6H2O, Hchp, PhPO3H2 2-(phosphonomethyl)-aminosuccinic acid (PMAS), CoCl2·xH2O, NaOH Na2MoO4, CoCl2, hedpH4 Co(ClO4)2·6H2O, Hchp, PhCH2PO3H2, Et3N Co(BF4)2·6H2O, Hchp, CH3PO3H2, Et3N Co(ClO4)2·6H2O, Hchp, EtPO3H2, Et3N Co(BF4)2·6H2O, Hchp, CH3(CH2)7PO3H2, Et3N [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Ln2(O2CBu-t)6(HO2CBu-t)6], (Ln = Gd, Tb, Dy, Ho), t-BuPO3H2, Et3N, NaOMe, NaOEt, KOH [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, t-BuPO3H2, Et3N, NaOMe, Y(NO3)3·xH2O (1-NH2-1-C6H10)PO3H2, [Co2(μ-OH2)(O2CBu-t)4(HO2CBu-t)4], [Ln2(O2CBu-t)6(HO2CBu-t)6], (Ln = Gd, Dy), Et3N Hchp, PhPO3H2, CoCl2·6H2O, NaOMe Co(NO3)2·6H2O, PhPO3H2, Hchp, NaOMe [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4], Et3N, Hchp, 3-chlorobenzylphosphonic acid Co(OAc)2·4H2O, H6E = (C6H6(CO2H)6·H2O, N-(phosphonomethyl)iminodiacetic acid, {H4L = (N(CH2CO2H)2(CH2PO3H)} [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, Hchp, p-NO2C6H4PO3H2

compounds [Co10(chp)6(O3PCH2Ph)2(O2CPh)8(F)2(H2O)2(EtOAc)2] [Co10(chp)8(O3PCH2Ph)2(O2CPh)8(F)2(MeCN)2](HNEt3)2 [Co10(chp)6(O3PCH2Ph)2(O2CBu-t)8(F)2(H2O)2(MeCOMe)2] [Co10(chp)6(O3PEt)2(O2CPh)8(F)2 (MeCN)4] [Co10(chp)8(Hchp)2(O3PCH2Nap)(O2CPh)7(OH)3(H2O)] [Co10(chp)6(O3PMe)2 (O2CBu-t)8(F)2(MeCN)4] [Co10(chp)12(O3PMe)2(O2CPh-2-Ph)4(H2O)4] [Co10(chp)6{O3P(CH2)7CH3}2(O2CPh)8(F)2(MeCN)4] [CoII8NdIII2(μ3-OH)2(O3PCH2Ph)4(O2CBu-t)12(HO2CMe)2]·(MeCN)6

reactants

Co(BF4)2·6H2O, Hchp, NEt3, PhCO2H, PhCH2PO3H2 Co(BF4)2·6H2O, Hchp, NEt3, PhCH2PO3H2 Co(BF4)2·6H2O, Hchp, NEt3, t-BuCO2H, PhCH2PO3H2 Co(BF4)2·6H2O, Hchp, NEt3, PhCO2H, EtPO3H2 Co(BF4)2·6H2O, Hchp, NEt3, PhCO2H, NapCH2PO3H2 Co(BF4)2·6H2O, Hchp, NEt3, t-BuCO2H, MePO3H2 Co(BF4)2·6H2O, Hchp, NEt3, HO2CPh-2-Ph, MePO3H2 Co(BF4)2·6H2O, Hchp, NEt3, PhCO2H, CH3(CH2)7PO3H2 [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, Nd(NO3)3, Et3N, H2O3PCH2Ph

Table 17. continued ref

50

239 241 253 258

1 22

46 237 254 255 237 237 237 237 1

21

1

21 237 238 242 50 253 237 170

1

242 242 242 242 242 242 242 242 1



phen, NH4VO3, Na2MoO4·2H2O, CoCl2·6H2O, H3PO3 Co(NO3)2·6H2O, Hchp, NaOMe, PhCH2PO3H2 Hchp, Co(NO3)2·6H2O, PhPO3H2, H2O2 6-methyl-2-pyridone (Hmhp), {Co(Piv)2}n, Na2O3PPh, NaOH

[CoII8LnIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16] (Ln = Gd, Tb, Dy, Ho, Er)

[CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Ln2(O2CBu-t)6(HO2CBu-t)6], t-BuPO3H2, Et3N, NaOMe, NaOEt, KOH [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, t-BuPO3H2, Et3N, NaOMe, Y(NO3)3·xH2O [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, t-BuPO3H2, Et3N, Yb(NO3)3·xH2O Co(NO3)2·6H2O, PhPO3H2, Hchp, NaOMe NH4VO3, phen, Co(OAc)2·4H2O, Na2WO4·2H2O, H3PO3 [Co4(phen)8(H2O)2(HPO3)2](H3O)3[PMoVI8VIV4O40(VIVO)2] [Co13Na6(chp)20(O3PCH2Ph)5(OH)2(MeCN)(H2O)(MeOH)] [Co20(O)2(OH)4(chp)26(PhPO3)4(H2O)6] [(μ-H2O)4Na12Co12(μ5,η2-O3PPh)4(μ6-O3PPh)4(μ3,η2-mhp)8(μ2-Piv)4(μ3-Piv)8]·1.25C10H22

[CoII8YIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16] [CoII8YbIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16] [Co14Na4(chp)20(O3PPh)6(Hchp)2(H2O)8] [Co4(HPO3)2(C12H8N2)8(H2O)2](H3O)[PWVI9VIV3O40(VIVO)2]·H2O

[Co15Na(chp)22(Hchp)2(O3PEt)3(OH)3(H2O)3(MeCN)3] [CoII8GdIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16]

Co(BF4)2·6H2O, Hchp, NaOMe, EtPO3H2 [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], t-BuPO3H2

compounds [Co16(OH)6(chp)22(O3PC6H9)2(H2O)4]

reactants

Co(ClO4)2·6H2O, Hchp, cyclohexenephosphonic acid (H2O3PC6H9), Et3N

Table 17. continued

-do-dooctadecanuclear heterometallic octadecanuclear -dononadecanuclear icosanuclear tetraicosanuclear

256 241 237 238

1 1 241 257

1

241 21

ref 248

nuclearity/structure hexadecanuclear/wheelshaped hexadecanuclear heterometallic hexadecanuclear -do-


Scheme 61. Synthesis of [HNEt3]2[Co2(η1-3,5Me2PzH)2Cl2(Cl3CPO3)2]244

Figure 106. D4R core of the Co II phosphonate, [Co 4 (Ph3CPO3)4Py4].45

Figure 107. Tetranuclear Co II phosphonate, (H 3 O) 6 ·[Co 4 (H2O)4(HPMIDA)2(PMIDA)2]·2H2O.245 Adapted from ref 245. Copyright 2005 Elsevier Masson SAS.

11.2. Ruthenium and Osmium

RuIII phosphonates are very few; most of these possess layered structures. Only three examples of molecular ruthenium(III) phosphonates are known (Table 16).232−235 The reaction of [Ru2(μ-O2CCH3)4(O2CCH3)2]·H·0.7H2O with HPhPO2H/ PhPO3H2 afforded dinuclear ruthenium phosphinate/phosphonate complexes, [Ru2(μ-O2CCH3)4(HPhPO2)2]H and [Ru2(μO2CCH3)4(PhPO3H)2]H·H2O.232 In both of these compounds, the phosphinate/phosphonate ligands do not play any role in elaborating the nuclearity of the compound and only serve as terminal ligands (Figure 102a and b). Recently, a paddle wheel-shaped diruthenium phosphonate complex, (H2pip)2[Ru2(hedp)2Cl2]·6H2O [pip = piperazine, hedpH4 = 1-hydroxyethylidenediphosphonic acid), CH3C(OH)(PO3)2], was prepared in the reaction of (NH4)3[Ru2(hedp)2]·2H2O, Na4[Ru2(hedp)2Cl]·16H2O, 35% peracetic

BG


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Figure 108. A heterometallic Na6Co5 phosphonate complex, [(μHPiv)2(μ2-Hmhp)4Na6Co5 (μ6,η2 -O3PPh)2(μ3 ,η2-Piv)2(μ3-Piv)3(μPiv)7]2·(C10H22) [Hmhp = 6-methyl-2-pyridone, Piv = t-BuCO2−].238 Adapted from ref 238. Copyright 2012 Elsevier Masson SAS. Figure 110. Molecular structure of [Co6(chp)6(Hchp)2(O3PBu-t)(O2CPh-2-Ph)3(F)(H2O)]·(HNEt3)·(Cl).242 Adapted from ref 242. Copyright 2012 The Royal Society of Chemistry.

Figure 111. A heterometallic hexanuclear Co4Gd2 phosphonate, [CoII4GdIII2(O3PBu-t)2(O2CBu-t)10(MeCN)2]·(MeCN)2.1 Adapted from ref 1. Copyright 2012 American Chemical Society.

Figure 109. Hexanuclear CoII phoshonate cage [Co6(chp)8(O3PBu-t)2(Hchp)2(H2O)2].237 Adapted from ref 237. Copyright 2008 American Chemical Society.

acid, and piperazine hydrochloride. In this complex, the [RP(O)2O(O)2PR]4− is involved in holding the ruthenium centers together (Figure 103).233 There are no reports on molecular osmium phosphonate complexes. However, a phosphinate complex, (μ-H)2Os3(CO)10(μ,η2-O2PPh2), is known (Figure 104).236

12. GROUP 9 PHOSPHONATES 12.1. Cobalt

Molecular cobalt phosphonates have received extensive attention. All of the reported compounds contain CoII ions except [Co20(O)2(OH)4(chp)26(PhPO3)4(H2O)6] (Hchp = 6-chloro-2hydroxypyridine),237 which contains 18 CoII and two CoIII ions. The nuclearity of homonuclear cobalt phosphonates varies from 1 to 20,237 while in the heterometallic systems the highest nuclearity achieved is 24.238 Winpenny and his co-workers have contributed extensively to the study of this family of compounds (homonuclear CoII and heterometallic CoII/LnIII)1,21,22,45,46,120,170,237,239−242 with a particular interest in studying their magnetic properties including magneto caloric effect (MCE).1,21,22,46,120

Figure 112. An octanuclear CoII phosphonate complex, [Et3NH][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2].237,240 Adapted from ref 240. Copyright 2005 The Royal Society of Chemistry.

A representative mononuclear CoII phosphonate, [Co(2,2′bipy)(hedpH3)2]·H2O or [Co(1,10-phen)(hedpH3)2]·H2O, is described below.243 This compound was prepared in the BH


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Figure 116. Decanuclear Co II phosphonate, [Co 10 (chp) 6 (O3PCH2Ph)2(O2CPh)8(F)2(H2O)2(EtOAc)2].242 Adapted from ref 242. Copyright 2012 The Royal Society of Chemistry.

Figure 113. A nonanuclear 30-membered macrocyclic CoII phosphonate complex, [Co9(3,5-Me2Pz)12(3,5-Me2PzH)6(Cl3CPO3)3]·(toluene)7.246 Adapted from ref 246. Copyright 2014 American Chemical Society.

Figure 114. Nonanuclear core of the CoII phosphonate, [Co9(chp)9(O3PBu-t)(O2CBu-t)6(OH)].242 Adapted from ref 242. Copyright 2012 The Royal Society of Chemistry. Copyright 2012 The Royal Society of Chemistry.

Figure 117. Line diagram of a heterometallic decanuclear Co4Gd6 phosphonate complex, [Co II 4 Gd III 6 (O 3 PCH 2 Ph) 6 (O 2 CBu-t) 14 (HO2CBu-t)x(MeCN)y(H2O)z].21

Figure 115. Core of a planar decanuclear CoII phosphonate, [Co10{2,3,5,6-(Me)4C6HCH2PO3}8{2,3,5,6-(Me)4C6HCH2PO3H}4Cl6]·6Et3NH·10nhexane·16H2O.247 Adapted from ref 247. Copyright 2014 Wiley-VCH Verlag GmbH & Co. KGaA. BI


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Figure 120. A fluoride-bridged dodecanuclear CoII phosphonate, [Co12(chp)15(O3PBu-t)(F)3(OH)4].241 Adapted from ref 241. Copyright 2009 The Royal Society of Chemistry. Figure 118. Undecanuclear core of the Co II phosphonate, [Co11(OH)(chp)18(FPO3)].237 Adapted from ref 237. Copyright 2008 American Chemical Society.

Figure 121. Line diagram of a heterometallic dodecanuclear Co8Dy4 complex, [CoII8GdIII4(O3PBu-t)6(O2CBu-t)16].1

The terminal pyrazole and chloride ligands help in fulfilling the coordination requirement of the CoII ions. Other dinuclear and heterometallic Co2Sb2 ensembles are summarized in Table 17. It may be noted that the Co2Sb2 ensemble has been described in the section on antimony phosphonates above. A tetranuclear CoII phosphonate cage, [Co4(Ph3CPO3)4Py4], containing a D4R core was prepared in the reaction of Co(OAc)2·6H2O with Ph3CPO3H2 in the presence of pyridine.45 All of the CoII ions are tetracoordinate due to the coordination action of [Ph3CPO3]2− and pyridine ligands. The phosphonate ligands are involved in a 3.111 bridging coordination mode (Figure 106). Similar types of cage structures of main-group as well as transition metals phosphonates are known, as discussed above.35,45,68,70,74,85,146,218,220 A tetranuclear Co II compound (H 3 O) 6 ·[Co 4 (H 2 O) 4 (HPMIDA)2(PMIDA)2]·2H2O has been synthesized in the reaction involving CoCl2·6H2O, H4PMIDA [H4PMIDA = N(phosphonomethyl)iminodiacetic acid], NH4F, and Me4NOH.

Figure 119. Core of a dodecanuclear Co II phosphonate, [Co12(Hchp)2(p-NO2C6H4PO3)4(O2CBu-t)12(CO3)4]·(CH3CN).50 Adapted from ref 50. Copyright 2013 American Chemical Society.

reaction of CoCl2·6H2O with 2,2′-bipyridine/1,10-phenanthroline and hedpH4 [hedpH4 = 1-hydroxyethylidenediphosphonic acid] under hydrothermal conditions.243 This compound contains a single CoII ion octahedrally coordinated by monodentate [hedpH3]− and chelating bipy/phen ligands (Figure 105). Other known mononuclear CoII phosphonate derivatives are listed in Table 17. The dinuclear CoII phosphonate ensemble, [HNEt3]2[Co2(η1-3,5-Me2PzH)2Cl2(Cl3CPO3)2], has been synthesized by a multicomponent reaction involving CoCl2, CCl3PO3H2, and 3,5-dimethylpyrazole (3,5-Me2PzH) in the presence of NEt3 as the base (Scheme 61).244 The dinuclear derivative possesses a central eight-membered puckered ring due to an isobidentate coordination action of [Cl3CPO3]2− ligands. BJ


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Figure 124. Molecular structure of the Na4Co14 phosphonate, [Co14Na4(chp)20(O3PPh)6(Hchp)2(H2O)8].241 Adapted from ref 241. Copyright 2009 The Royal Society of Chemistry.

Figure 122. A tridecanuclear Co II complex, [Co 13 (OH) 3 (chp)19(O3PPh)2(H2O)2(EtOAc)2].46 Adapted from ref 46. Copyright 2001 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 125. Molecular structure of a CoII4DyIII10 complex, [Co4Dy10(O2CBu-t)12(O3PC6H10NH2)8(PO4)2(O2CMe)2(O3PC6H10NH3)2].22 Adapted from ref 22. Copyright 2013 The Royal Society of Chemistry.

coordination action of [PhPO3]2− and t-BuCO2− ligands (Figure 108).238 A hexanuclear planar CoII phosphonate, [Co6(chp)8(O3PBu-t)2(Hchp)2(H2O)2],237 has been synthesized in the reaction involving Co(NO 3 ) 2 ·6H 2 O, 6-chloro-2-hydroxypyridine (Hchp), and t-BuPO3H2 (Figure 109). The structure of this compound reveals the presence of two symmetrical Co3 motifs that are connected to each other by the bridging oxygen atoms of the chp ligands. Each of the Co3 subunits is held by the capping 3.111 coordination mode of the [t-BuPO3]2− ligand. In contrast to the above, in a different hexanuclear CoII phosphonate, [Co 6 (chp) 6 (Hchp) 2 (O 3 PBu-t)(O 2 CPh-2Ph)3(F)(H2O)]·(HNEt3)·(Cl), the [t-BuPO3]2− ligand is involved in a 6.222 bridging coordination action.242 The periphery of the hexametallic core is tied together by the remaining ligands (Figure 110). In the heterometallic complex, [CoII4GdIII2(O3PBu-t)2(O2CBu-t)10(MeCN)2]·(MeCN)2, the two [t-BuPO3]2− ligands

Figure 123. Molecular structure of [Co 1 4 (OH) 4 (chp) 2 (O3PCh2Ph)2(H2O)2].237 Adapted from ref 237. Copyright 2008 American Chemical Society.

This compound contains four CoII ions, two [HPMIDA]−, and two [PMIDA]2− ligands.245 The four CoII ions lie in a plane and are bound by tetradentate chelating PMIDA, along with two HPMIDA ligands (Figure 107). The reaction of {Co(Piv)2}n, Na2O3PPh, Hmhp, and NaPiv afforded a heterometallic Na6Co5 complex, [(μ-HPiv)2(μ2Hmhp)4Na6Co5(μ6,η2-O3PPh)2(μ3,η2-Piv)2(μ3-Piv)3(μ-Piv)7]2· (C10H22) [Hmhp = 6-methyl-2-pyridone, Piv = t-BuCO2−].238 This compound contains six NaI and five CoII ions that are held together by the bridging coordination action of [PhPO3]2−, t-BuCO2−, and four neutral [Hmhp] ligands. The molecular structure of this compound contains a central CoII ion that is fused with two identical [Na3Co2] subunits by the bridging BK


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Figure 128. Molecular structure of a hexadecanuclear CoII complex, [Co16(OH)6(chp)22(O3PC6H9)2(H2O)4],248 showing the fusion of two symmetry-related octanuclear units. Adapted from ref 248. Copyright 2010 The Royal Society of Chemistry.

Figure 126. Pentadecanuclear core of [Co 15 (chp) 8 (Hchp)(O3PR)8(O2CBu-t)6(CH3CN)3]·(CH3CN).50 Adapted from ref 50. Copyright 2013 American Chemical Society.

Figure 127. Heterometallic Co15Na phosphonate complex, [Co15Na(chp)22(Hchp)2(O3PEt)3(OH)3(H2O)3(MeCN)3],241 revealing three pentanuclear CoII motifs linked to a central sodium ion. Adapted from ref 241. Copyright 2009 The Royal Society of Chemistry.

Figure 129. Core structure of [CoII8GdIII8(μ3-OH)4(NO3)4(O3PBut)8(O2CBu-t)16].21 Adapted from ref 21. Copyright 2011 The Royal Society of Chemistry.

are involved in fusing two trimetallic Co2Gd units together by means of a 4.221 coordination (Figure 111).1 An octanuclear CoII phosphonate, [Et3NH][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2], has been prepared in the reaction of Co(NO3)2·6H2O, PhPO3H2, and 6-chloro-2hydroxypyridine (Hchp) in the presence of NEt3. The molecular structure of this compound contains two symmetrical Co4 subunits that are connected to each other by the bridging [PhPO3]2−, [NO3]−, and [chp]− ligands (Figure 112).237,240 The multicomponent reaction of Co(ClO4)2·6H2O with (trichloromethyl)phosphonic acid [CCl3PO3H2] and 3,5dimethylpyrazole [3,5-Me2PzH] in the presence of NEt3 afforded [Co9(3,5-Me2Pz)12(3,5-Me2PzH)6(Cl3CPO3)3]·(toluene)7.246 The structure of this compound reveals three trinuclear (Co3) subunits that are connected to each other through three bridging [Cl3CPO3]2− ligands resulting in a 30-membered macrocycle. Each of the Co3 motifs of the macrocycle is identical and contains three cobalt atoms and six pyrazole ligands. The two cobalt atoms of each of the three Co3

motifs are connected by the bridging coordination mode of the pyrazole ligand (Figure 113). The reaction of Co(BF4)2·6H2O, Hchp, t-BuPO3H2, and t-BuCO2H in the presence of NEt3 afforded the nonanuclear Co II phosphonate cage, [Co 9 (chp) 9 (O 3 PBu-t)(O 2 CBut)6(OH)].242 This compound contains two layers, the top layer being a planar hexagonal ring containing a single [t-BuPO3]2−ligand that binds to the hexametallic core in a 6.222 mode. Three [t-BuCO2]− ligands bridge alternate edges of the hexagon, while the remaining edges are bridged by three [chp]− ligands (Figure 114). The bottom layer contains a triangular core bridged by a μ3-OH; further, [t-BuCO2]− ligands assist in holding the three CoII ions together. The top and bottom layers are connected to each other through the 3.31 bridging coordination action of [chp]− ligands (Figure 114). Several decanuclear CoII phosphonates are known possessing varying structures. These have been prepared by changing the reaction conditions, stoichiometry, and nature of the BL


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Review

Figure 130. An icosanuclear mixed-valent cobalt phosphonate complex, [Co20(O)2(OH)4(chp)26(PhPO3)4(H2O)6].237 Adapted from ref 237. Copyright 2008 American Chemical Society.

phosphonate ligands. Representative examples are described here. A planar decanuclear molecular CoII phosphonate cage, [Co10{2,3,5,6-(Me)4C6HCH2PO3}8{2,3,5,6-(Me)4C 6HCH2PO3H}4Cl6]·6Et3NH·10n-hexane·16H2O, was isolated in the multicomponent reaction of CoCl2 with 2,3,5,6-Me4C6HCH2PO3H2 in the presence of Et3N as the base.247 The structure of this compound comprises two symmetric Co5 motifs that are connected to each other by two [2,3,5,6-(Me)4C6HCH2PO3]2− and two [2,3,5,6(Me)4C6HCH2PO3H]− ligands (Figure 115). Another decanuclear phosphonate cage, [Co10(chp)6(O3PCH2Ph)2(O2CPh)8(F)2(H2O)2(EtOAc)2], was prepared in the reaction of Co(BF4)2·6H2O, Hchp, PhCH2PO3H2, PhCO2H, and NEt3.242 This cage contains two Co5 subunits that are connected to each other by a 6.222 coordination binding mode of the [PhCH2PO3]2− ligands. Each of the Co5 motifs is held together by the multiple coordination action of [hcp]−, [F]−, and [PhCO2]− ligands (Figure 116). Heterometallic decanuclear complexes are also known in the literature containing varying numbers of CoII or LnIII.1,21 These have been prepared utilizing the cluster expansion strategy, using [Co I I 2 (μ-OH 2 )(O 2 CBu-t) 4 ]·(HO 2 CBu-t) 4 and [Ln2(O2CBu-t)6(HO2CBu-t)6] as the starting materials. A representative heterometallic complex, [Co II 4 Gd I II 6 (O3PCH2Ph)6(O2CBu-t)14(HO2CBu-t)x(MeCN)y(H2O)z],21 is described. This compound contains four CoII and six GdIII ions that are connected to each other by the bridging coordination action of [PhCH2PO3]2− and [t-BuCO2]− ligands. The molecular structure of this compound has been described as a 3 × 3 grid containing Co2Gd, Gd3, and Co2Gd2 (the dinuclear cobalt unit has been considered by the authors as a single structural element for this description) motifs that are linked by a 4.221 coordination binding mode of the [PhCH2PO3]2− ligands (Figure 117). The undecanuclear CoII fluorophosphonate complex, [Co11(OH)(chp)18(FPO3)], has been synthesized in the reaction of Co(BF4 )2 ·6H2O, 6-chloro-2-hydroxypyridine (Hchp), and FPO3H2 in the presence of NEt3.237 The structure of this compound contains three layers, the top layer consisting of a missing-vertex cube [four CoII], a central layer consisting of six CoII, and a unique CoII in the bottom. The [FPO3]3− ligands bind in a 9.3222 binding mode where the fluoride substituent

Figure 131. A heterometallic DyIr6 phosphonate, [DyIr6(ppy)12(bpp)2(bppH)4]·(CF3SO3)·8H2O [ppyH = 2-phenylpyridine, bpp2− = 2-pyridylphosphonate),259 containing a central DyIII surrounded by six IrIII centers. Adapted from ref 259. Copyright 2014 The Royal Society of Chemistry.

also takes part in a bridging coordination (Figure 118). A similar type of complex, [Co11(OH)(chp)18(PO4)], is also formed with pyrophosphate ligands.237 The dodecanuclear CoII phosphonate [Co12(Hchp)2(p-NO2C6H4PO3)4(O2CBu-t)12(CO3)4]·(CH3CN) [R = p-nitrobenzyl], has been prepared utilizing a cluster expansion strategy involving the reaction of [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBut)4, Hchp, and p-NO2C6H4PO3H2.55 This compound contains 12 octahedral CoII ions that are held together by four μ3-O, four [p-NO2C6H4PO3]2−, four [t-BuCO2]−, four [CO3]2−, and two [Hchp] ligands. The core of this compound possesses four interlinked triangular subunits (Figure 119). The fluoride-bridged dodecanuclear CoII phosphonate ensemble, [Co12(chp)15(O3PBu-t)(F)3(OH)4], was synthesized in the reaction of Co(NO3)2·6H2O, Hchp, t-BuPO3H2, and BM


Chemical Reviews

Review

Figure 132. A mononuclear NiII phosphonate, [Ni(hedpH2)3· 3NH2(CH3)2NH(CH3)3·3H2O.211 Adapted from ref 211. Copyright 2013 The Royal Society of Chemistry.

Figure 133. A dinuclear NiII phosphinate complex [Ni2(μ-O2P(H)Mes)2(bipy)4]Br2.261 Adapted from ref 261. Copyright 2011 American Chemical Society.

NaOMe.241 This compound comprises two Co6 subunits that are connected to each other through bridging F− and HO− ligands. The top Co6 layer is capped by a 6.222 coordination binding mode of the [t-BuPO3]2− ligand, while the bottom Co6 unit does not have coordination through the phosphonate ligand (Figure 120). The heterometallic dodecanuclear complex, [CoII8GdIII4(O3PBu-t)6(O2CBu-t)16], was prepared in the reaction of [Co II 2 (μ-OH 2 )(O 2 CBu-t) 4 ]·(HO 2 CBu-t) 4 , [Ln 2 (O 2 CBut)6(HO2CBu-t)6], t-BuPO3H2, and NaOMe.1 This compound possesses a [4 × 3] grid type structure where eight CoII and four GdIII ions are held together by the multiple coordination action of the [t-BuPO3]2− and [t-BuCO2]− ligands. The central row of the grid contains four cobalt(II) ions, and the outer rows of the grid are occupied by another four cobalt(II) ions and four GdIII ions (Figure 121). Interestingly, the reaction of cobalt hydroxide and PhPO3H2 in the presence of Hchp afforded a tridecanuclear CoII phosphonate cluster, [Co13(OH)3(chp)19(O3PPh)2(H2O)2(EtOAc)2].46,237 The unusual {Co13} cage contains 13 CoII ions that are held together by three [OH]−, 19 [chp]−, and two [PhPO3]2− ligands. The latter bind in a 5.221 coordination mode (Figure 122). The multicomponent reaction of Co(ClO 4 ) 2 ·6H 2 O, PhCH2PO3H2, and Hchp in the presence of NEt3 afforded a tetradecanuclear CoII phosphonate cage, [Co14(OH)4(chp)2(O3PCh2Ph)2(H2O)2], containing two peripheral Co5 subunits and a central Co4 motif.237 The Co5 motif is formed by edgesharing of two incomplete cubes, with one CoII being involved in a corner sharing mode. The four central CoII ions lie symmetrically vis-a-vis the two Co5 units. [PhCH2PO3]2−, [μ3O]2−, and [chp]− ligands are all involved in fusing the subunits together (Figure 123). The heterometallic Na 4 Co 14 cage, [Co 14 Na 4 (chp) 20 (O3PPh)6(Hchp)2(H2O)8], was obtained in the reaction of the Co(NO3)2·6H2O, PhPO3H2, Hchp, and NaOMe.241 This compound contains two symmetrical Co6Na2 subunits that are connected to a central Na4 core. Two other CoII ions are separately located and connect the two Co6Na2 subunits through [PhPO3]2− and [chp]− ligands (Figure 124). Several heterometallic (CoII/LnIII) tetradecanuclear phosphonate cages with varying number of CoII ions or LnIII ions

Figure 134. A tetranuclear Ni II phosphonate, (H 3 O) 8 [Ni 4 O2(HPMIDA)4(H2O)2].262 Adapted from ref 262. Copyright 2009 Elsevier Masson SAS.

known.1,22 For example, a tetradecametallic Co/Ln phosphonate cage, [Co4Dy10(O2CBu-t)12(O3PC6H10NH2)8(PO4)2(O2CMe)2(O3PC6H10NH3)2], has been synthesized in the reaction of [Co 2 (μ-OH 2 )(O 2 CBu-t) 4 (HO 2 CBu-t) 4 ], [Ln2(O2CBu-t)6(HO2CBu-t)6], and (1-NH2-1-C6H10)PO3H2 in the presence of NEt3.22 The structure of this compound contains two symmetry related Co2Dy4 motifs and two other DyIII ions that lie on the inversion center of the cage (Figure 125). The reaction of [Co2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4], 3chlorobenzylphosphonic acid, Hchp, and Et3N under solvothermal conditions resulted in a pentadecanuclear CoII cage [Co 1 5 (chp) 8 (Hchp)(O 3 PR) 8 (O 2 CBu-t) 6 (CH 3 CN) 3 ]· (CH3CN) (R = 3-chlorobenzyl) where the central part contains BN


Chemical Reviews

Review

Figure 135. Octanuclear core of a NiII phosphonate, [Ni8(μ3OH)4(μ2-OH2)2(O3PCH2C6H5)2(O2CBu-t)8(HO2CBu-t)6].263 Adapted from ref 263. Copyright 2007 The Royal Society of Chemistry.

Figure 137. Molecular structure of [Ni10(chp)6(O3PCH2Nap)2(Piv)8(F)2(MeCN)2(H2O)2].264 Adapted from ref 264. Copyright 2014 American Chemical Society.

Figure 136. Nonanuclear core of [Ni 9 (μ 3 -OH) 3 (μ 2 -OH 2 )(HO 3 PCH 2 C 6 H 5 )(O 3 PCH 2 C 6 H 5 )(chp) 4 (O 2 CBu-t) 8 (HO 2 CBut)2(H2O)], held together by two phosphonate ligands.263 Adapted from ref 263. Copyright 2007 The Royal Society of Chemistry.

four phosphonate ligands while a pair of phosphonate ligands are present on either side (Figure 126).50 The heterometallic CoII phosphonate complex, [Co15Na(chp)22(Hchp)2(O3PEt)3(OH)3(H2O)3(MeCN)3], was obtained in the reaction of Co(BF4)2·6H2O, Hchp, EtPO3H2, and NaOMe.241 This compound possesses 15 CoII ions and a single sodium ion that are held together by [chp]−, [Hchp], [EtPO3]2−, and μ-OH ligands. The molecular structure of this compound contains a central sodium ion, which is linked to three pentametallic subunits through the bridging coordination of three [EtPO3]2− and three μ-OH ligands (Figure 127). The reaction of Co(ClO4)2·6H2O with Hchp and cyclohexenephosphonic acid (C6H9PO3H2) in the presence of NEt3 afforded a hexadecanuclear Co II phosphonate cage, [Co16(OH)6(chp)22(O3PC6H9)2(H2O)4].248 Two symmetryrelated Co8 subunits are attached to each other through two [chp]− ligands. Within each subunit, four CoII ions are bridged to each other by a phosphonate ligand (Figure 128). An interesting heterometallic Co 8 Gd 8 phosphonate, [Co II8Gd III8(μ3-OH) 4(NO3 ) 4(O 3PBu-t) 8(O2 CBu-t)16], has been synthesized in the reaction involving [CoII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], and t-BuPO3H2.21 This compound contains a central [2 × 2]

Figure 138. Fusion of three tetranuclear motifs in the dodecanuclear core of [Ni12(μ3-OH)4(μ6-O3PC6H5)4(μ2-O2CBu-t)12(μ2-L)6].263 Adapted from ref 263. Copyright 2007 The Royal Society of Chemistry.

{Co4} square grid formed by the intervention of bridging NO3− ligands. The central Co4 square grid is connected to the outer {Gd8Co4} unit by four μ3-OH and eight [t-BuPO3]2− ligands (Figure 129). An icosanuclear mixed-valent cobalt phosphonate cage, [Co20(O)2(OH)4(chp)26(PhPO3)4(H2O)6],237 was obtained in the reaction of Co(ClO4)2·6H2O, Hchp, PhPO3H2, and NEt3 in the presence of H2O2. It has been suggested that this compound contains 18 Co II and 2 Co III ions. The centrosymmetric icosanuclear cluster contains two Co10 motifs. Each of the Co10 subunits is held by the multiple bridging coordination of the [PhPO3]2−, [μ3-O]2−, and [chp]− ligands. Interestingly, the two Co10 subunits are connected to each other by only bridging [μ3-O]2− and [μ3-OH]− ligands, without the intervention of the phosphonate ligands (Figure 130). BO


Chemical Reviews

Review

Table 18. Molecular Nickel Phosphonates reactants 1-hydroxyethylidene diphosphonic acid (hedpH4), bipy, Ni (OAc)2·4H2O hedpH4, phen, Ni(OAc)2·4H2O hedpH4, Ni(OAc)2·4H2O disodium bisphosphonates pamidronate (Na2Pam), NiCl2·6H2O, HCl N,N′-dimethyl-N,N′-ethylenediaminebis (methylenephosphonic acid) (H4L), Me4NCl, NiCl2·6H2O NiSO4·7H2O, bipy, 4,4′dimethylenebiphenyldiphosphonic acid (H4dbp) imidazole (Im), 1-aminoethylidenediphosphonic acid (AEDPH4), Ni(OH)2 AEDPH4, Ni(OH)2, ethylenediamine (en), Ni (OAc)2·4H2O AEDPH4, Ni(OH)2, NH3·H2O, Ni(OAc)2·4H2O Ni(NO3)2·6H2O, 1,4,7,10-tetrakis-(methylenephosphonic acid)-1,4,7,10-tetraazacyclododecane {C3NH6(PO3H2)}4 Ni(NO3)2·6H2O, NaOH, N-(phosphonomethyl) glycine N-(phosphonomethyl) iminodiacetic acid (H4PMIDA), NiCl2·6H2O, N-methylpiperazine, NH4F [Ni2(H2O)(O2CBu-t)4(HO2CBu-t)4], C6H5CH2PO3H2, NEt3 [NiII2(μ-OH2)(O2CBu-t)4(HO2CBu-t)4], p-tertbutylbenzylphosphonic acid, Et3N [Ni2(H2O)(O2CBu-t)4(HO2CBu-t)4], C6H5CH2PO3H2, Hchp Ni(BF4)2·6H2O, pivalic acid (HPiv), Hchp, t-BuPO3H2, NEt3 Ni(BF4)2·6H2O, HPiv, Hchp, PhCH2PO3H2, NEt3 Ni(BF4)2·6H2O, HPiv, Hchp, MePO3H2, NEt3 Ni(BF4)2·6H2O, HPiv, Hchp, NapCH2PO3H2, NEt3 [Ni2(H2O)(O2CBu-t)4(HO2CBu-t)4], PhPO3H2 [NiII2(μ-OH2)(O2CBu-t)4(HO2CBu-t)4], Et3N, p-tertbutylphenyl phosphonic acid pivalic acid (HPiv), Hchp, Ni(BF4)2·6H2O, PhPO3H2, NEt3 [Ni9(OH)6(Piv)12(HPiv)4], 6-methyl-2-hydroxypyridine (Hmhp), K2O3PPh, HPiv [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Gd2(O2CBu-t)6(HO2CBu-t)6], MePO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Gd2(O2CBu-t)6(HO2CBu-t)6], PhPO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Gd2(O2CBu-t)6(HO2CBu-t)6], n-C6H13PO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Gd2(O2CBu-t)6(HO2CBu-t)6], n-C8H17PO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Gd2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Y2(O2CBu-t)6(HO2CBu-t)6], MePO3H2, NEt3 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Y2(O2CBut)6(HO2CBu-t)6], NEt3, n-C6H13PO3H2 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Y2(O2CBu-t)6(HO2CBu-t)6], NEt3, n-C8H17PO3H2 [Ni2(μ2-OH2)(O2CBu-t)4(HO2CBu-t)4], [Y2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2, NEt3 [NiII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Dy2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2, NEt3 [NiII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Gd2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2, NEt3 [NiII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Y2(O2CBu-t)6(HO2CBu-t)6], PhCH2PO3H2, NEt3 2-(phosphonomethyl)- aminosuccinic acid (PMAS), NaOH, NiSO4 UO2(NO3)2·6H2O, Ni(CH3COO)2·4H2O, diethyl(2ethoxycarbonylphenyl) phosphonate, HF

compounds


ref

[Ni(bipy)(hedpH3)2]·H2O

mononuclear

266

[Ni(phen)(hedpH3)2]·H2O [Ni(hedpH2)3·3NH2(CH3)2NH (CH3)3·3H2O [NiII(Pam)2(H2O)2]

-do-do-do-

266 221 250

[Ni(H2L)(H2O)2]

-do-

266

[Ni(bipy)2(H2dbp)(H2O)]·H2O

-do-

267

[Ni(Im)6]3(AEDP)2(ImH)2]·24H2O

-do-

268

(enH2)3[Ni(AEDP)2]·6H2O

-do-

269

(NH4)6[Ni(AEDP)2]·4H2O [Ni{C3NH6(PO3H)}4{Ni(H2O)6}]

-do-do-

269 270

[Ni(O2CCH2NHCH2PO3H)2]·[Ni(H2O)6]·3.3H2O (H3O)8[Ni4O2(HPMIDA)4(H2O)2]

-dotetranuclear

271 262

[Ni8(μ3-OH)4(μ2-OH2)2(O3PCH2C6H5)2(O2CBut)8(HO2CBu-t)6] [Ni8(μ3-OH)4(OMe)2(O3PR)2(O2CBu-t)6(HO2CBu-t)8] (R = p-tert-butylphenyl) [Ni9(μ3-OH)3(μ2-OH2)(HO3PCH2C6H5)(O3PCH2C6H5) (chp)4(O2CBu-t)8(HO2CBu-t)2(H2O)] [Ni10(chp)4(Hchp)4.5(O3PBut)3(Piv)5(HPiv)2(OH)6(H2O)4.5] (HNEt3)·0.5MeCN·2.5H2O [Ni10(chp)6(O3PCH2Ph)2(Piv)8(F)2(MeCN)4] [Ni10(chp)6(O3PMe)2(Piv)8(F)2(MeCN)4]·5MeCN·2H2O [Ni10(chp)6(O3PCH2Nap)2(Piv)8(F)2(MeCN)2(H2O)2] [Ni12(μ3-OH)4(μ6-O3PC6H5)4(μ2-O2CCMe3)12(μ2-L)6], L = mixture of HO2CMe, HO2CBu-t, H2O, MeCN [Ni12(μ3-OH)4(HCO3)6(O3PR)4(O2CBu-t)6(HO2CBu-t)6] (R = p-tert-butylphenyl) [Ni12(chp)12(Hchp)2(PhPO3)2(Piv)5(HPiv)2(OH)2(H2O)6]· (F)·4.5MeCN·2H2O [(μ2-Hmhp)6Ni12(μ3-OH)4(μ6-O3PPh)4(μ2Piv)12]·7.5MeCN·1.5THF [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PMe)6(O2CBu-t)16]

octanuclear

263

-do-

253

nonanuclear

263

decanuclear

264

-do-do-dododecanuclear

264 264 264 263

-do-

253

-do-

264

-do-

272 23

[Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PPh)6(O2CBu-t)16]

heterometallic dodecanuclear/ Wells−Dawson type of core -do-

23

[Ni6Gd6(μ3-OH)2(μ2-OAc)2(n-C6H13PO3)6(O2CBu-t)16]

-do-

23

[Ni6Gd6(μ3-OH)2(μ2-OAc)2(n-C8H17PO3)6(O2CBu-t)16]

-do-

23

[Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PCH2Ph)6(O2CBu-t)16]

-do-

23

[Ni6Y6(μ3-OH)2(μ2-OAc)2(O3PMe)6(O2CBu-t)16]

-do-

23

[Ni6Y6(μ3-OH)2(μ2-OAc)2(n-C6H13PO3)6(O2CBu-t)16]

-do-

23

[Ni6Y6(μ3-OH)2(μ2-OAc)2(n-C8H17PO3)6(O2CBu-t)16]

-do-

23

[Ni6Y6(μ3-OH)2(μ2-OAc)2(O3PCH2Ph)6(O2CBu-t)16]

-do-

23

[NiII6DyIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16 (MeCO2H)2]·(MeCN)4 [NiII6GdIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16 (MeCO2H)2]·(MeCN)4 [NiII6YIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16 (MeCO2H)2]·(MeCN)4 Na[Ni12(PMAS)6(H2O)17(OH)]·xH2O

-do-

20

-do-

20

-do-

20

tridecanuclear

254

icosanuclear

260

[H3O]4[Ni(H2O)3]4[Ni{(UO2) (PO3C6H4CO2)}3(PO4H)]4·2.72H2O BP


Chemical Reviews

Review

Figure 141. A mononuclear PdII phosphonate complex, [(DcpOMe)PdAr2PC6H4PO2(OH)].273 Adapted from ref 273. Copyright 2007 The Royal Society of Chemistry.

Figure 139. A heterometallic Ni6Gd6 phosphonate complex, [Ni I I 6 Gd I I I 6 (OH) 2 (O 3 PCH 2 Ph) 6 (O 2 CBu-t) 1 6 (MeCO 2 H) 2 ](MeCN)4.20 Adapted from ref 20. Copyright 2011 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 142. A tridecanuclear phosphonate complex, Na 6 [CuIIO8PdII12(PhPO3)8]·35H2O, containing a central CuII.274 Adapted from ref 274. Copyright 2012 American Chemical Society.

connection between the two is achieved through six bridging phosphonate ligands (Figure 131).

13. GROUP 10 PHOSPHONATES 13.1. Nickel

Figure 140. A heterometallic Ni 8 U12 phosphonate complex, [H 3 O] 4 [Ni(H 2 O) 3 ] 4 [Ni{(UO 2 )(PO 3 C 6 H 4 CO 2 )} 3 (PO 4 H)] 4 · 2.72H2O.260 Adapted from ref 260. Copyright 2012 American Chemical Society.

The nuclearity of homometallic NiII phosphonates varies from 1 to 12, while in the heterometallic system the highest nuclearity achieved is 20.260 A mononuclear Ni II phosphonate, [Ni(hedpH 2 ) 3 · 3NH2(CH3)2NH(CH3)3·3H2O, has been synthesized in the reaction of Ni(OAc)2·4H2O with hedpH4 [hedpH4 = 1hydroxyethylidenediphosphonicacid].211 Three [hedpH2]2− ligands bind in a chelating mode around the NiII center (Figure 132). There are no reports of dinuclear NiII phosphonates. On the other hand, NiII phosphinates are known. For example, [Ni2(μ-O2P(H)Mes)2(bipy)4]·Br2 was obtained in the reaction involving [NiBr2(bipy)2] and MesP(H)(O)OH.261 This compound possesses a centrosymmetric structure where the two NiII centers are bridged by two [P(H)ArMesO2]− ligands (Figure 133). The bridging coordination of the phosphinate

Information on all CoII phosphonates including heterometallic derivatives is given in Table 17.237−258 12.2. Rhodium and Iridium

Rhodium phosphonates are completely unknown. A mixedmetal DyIr6 phosphonate, [DyIr6(ppy)12(bpp)2(bppH)4]· (CF3SO3)·8H2O [ppyH = 2-phenylpyridine, bpp2− = 2pyridylphosphonate), is known and has been prepared in the reaction of [Ir(ppy)2(bppH)] and Dy(CF3SO3)3 under microwave conditions.259 The structure of this compound reveals a central DyIII ion that is surrounded by six IrIII subunits; the BQ


Chemical Reviews

Review

Table 19. Molecular Palladium Phosphonates reactants

compounds

2-diphenylphosphinophenyl phosphonic acid (Ar2PC6H4PO3H2) (Ar = Ph, o-MeC6H4), Na2CO3, [(Dcp-OMe)PdCl]2 (Dcp = dicyclopentadiene) [Pd3(CH3CO2)6], PhPO3H2, Cu(CH3CO2)2·H2O, ZnCl2, NaOH


ref

[(Dcp-OMe)PdAr2PC6H4PO2(OH)]

mononuclear

273

Na6[CuIIO8PdII12(PhPO3)8]·35H2O, Na6[ZnIIO8PdII12(PhPO3)8]·36H2O

heterometallic dodecanuclear

274

Table 20. Molecular Platinum Phosphonates reactants

compounds


ref

cis-[PtCl2(PPh3)2], FcCH2P(O)(OH)2, [Fc = (η5-C5H4)Fe(η5-C5H5)], Ag2O cis-[PtCl2(PPh3)2], FcCH2CH2P(O)(OH)2, [Ag2O] cis-[PtCl2L2], L = PPh3, endo-8-camphanyl-phosphonic acid (C10H17PO3H2), Ag2O cis-[Pt(CH3)2(OD)]2− N-phosphonomethy1)glycine (HIMPA), KOH, AgNO3 HIMPA, NaOH, [{Pt(CH3)2(OH)2(H2O)1.5}n], AgNO3 HIMPA, [{Pt(CH3)3}2(SO4)(H2O)4], [PtBr(CH3)2(H2O)3]·(NO3), KOH, AgNO3 HIMPA, [PtBr(CH3)2(H2O)3]·(NO3), KOH, AgNO3 HIMPA, [PtBr(CH3)2(H2O)3]·(NO3), KOH, AgNO3 HIMPA, [PtBr(CH3)2(H2O)3]·(NO3), KOH, AgNO3 camphenylphosphonic acid (C10H17PO3H2), cis-[PtCl2(PPh3)2], Ag2O phosphonoformic acid (PFA), cis-PtII(NH3)2Cl2, AgNO3, NaOH phosphonoformic acid (PFA), Pt(trans-l-dach)C1, diaminocyclohexane (dach), AgCl, NaOH cis-[PtCl2(PPh3)2], Ag2O, 1,1′-Fc′[P(O)(OH)2]2 methylene diphosphonate (MDP), AgCl, Pt(cis-dach)Cl2, diaminocyclohexane (dach), NaOH

[FcCH2PO3Pt(PPh3)2] [FcCH2CH2PO3Pt(PPh3)2] [Pt(O3PC10H17)(PPh3)2]·2CHCl3 [Pt(CH3)2(OD)2(IMPA-N,O)]3− Na[Pt(CH3)3(HIMPA)] [Pt(CH3)3(HIMPA)(H2O)]·H2O Ag3[PtBr(CH3)2(HIMPA)] [PtBr(CH3)2(HIMPA)]·1.5H2O Ag[PtBr(CH3)2(Himpa)] [Pt{O3PC10H17}(PPh3)2] [cis-Pt(NH3)2(PFA)] Na[Pt(trans-l-dach)(PFA)] [1,1′-Fc′{PO3Pt(PPh3)2}2] [Pt2(cis-dach)2(MDP)

mononuclear -do-do-do-do-do-do-do-do-do-do-dodinuclear -do-

275 275 277 278 278 278 278 278 278 276 279 279 275 279

Figure 143. (a) Mononuclear PtII phosphonate, [FcCH2PO3Pt(PPh3)2], and (b) a dinuclear PtII compound, [1,1′-Fc′{PO3Pt(PPh3)2}2], formed by the bridging action of a ferrocenediphosphonate ligand.275 Adapted from ref 275. Copyright 2001 Elsevier Masson SAS.

Figure 144. Molecular di- and trinuclear CuII phosphonate complexes, (a) [Cu2(μ2-CCl3PO3)2(bipy)2(MeOH)2]·(H2O)187 and (b) [Cu3(C5H9PO3)2(bipy)3(MeOH)(H2O)]·(ClO4)2.282

ligands results in the formation of a puckered eight-membered P−O−Ni heterocyclic ring. Similar types of phosphonate

bridged dinuclear compounds involving other transition metal ions are known. These have been described vide supra. BR


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Figure 145. Tetranuclear CuII phosphonates (a) [Cu4Cl4(MePO3)2(3,5-Me2PzH)6];58 (b) [Cu4(μ-OH)(μ3-C6H11PO3)2(phen)4(H2O)2](NO3)3;283 (c) [Cu4(μ3 -OH)2{ArPO2(OH)}2(CH3CO2)2(3,5-Me 2PzH)4 ][CH3COO]2·CH2 Cl2;63,194 (d) [Cu 2(3,5-t-Bu 2PzH)2(t-BuPO3)2] 2;35 and (e) [Cu4(OH)(Ph3CPO3)3(Ph3CPO2OH).45

The reaction of NiCl2·6H2O with H4PMIDA [H4PMIDA = N-(phosphonomethyl)iminodiacetic acid], NH4F, and Nmethylpiperazine results in a tetranuclear NiII phosphonate, (H3O)8[Ni4O2(HPMIDA)4(H2O)2].262 The latter is assembled by the multiple coordination of both phosphonate and carboxylate ligands (Figure 134). An octanuclear NiII phosphonate complex, [Ni8(μ3-OH)4(μ2OH2)2(O3PCH2C6H5)2(O2CBu-t)8(HO2CBu-t)6], was obtained in the reaction of [Ni2(H2O)(O2CBu-t)4(HO2CBu-t)4] and C6H5CH2PO3H2.263 The molecular structure of this compound contains two butterfly shaped {Ni4(μ-OH)2} motifs that are held together through the bridging action of [PhCH2PO3]2− ligands (5.221 coordination binding mode) (Figure 135). A nonanuclear NiII phosphonate cage, [Ni9(μ3-OH)3(μ2OH 2)(HO 3PCH 2C 6H 5)(O 3PCH 2C 6H 5)(chp) 4(O 2CBu-t) 8(HO 2CBu-t) 2(H 2O)], has been synthesized in the reaction

of [Ni2(H2O)(O2CBu-t)4(HO2CBu-t)4], C6H5CH2PO3H2, and Hchpat under ambient reaction conditions.263 The irregular shaped nonanuclear cage consists of Ni5 and Ni4 subunits. These two subunits are connected to each other through the bridging phosphonate, [chp]−, and pivalate ligands (Figure 136). A symmetrical decanuclear NiII phosphonate complex, [Ni10(chp)6(O3PCH2Nap)2(Piv)8F)2(MeCN)2(H2O)2], has been isolated in the reaction of Ni(BF4)2·6H2O, pivalic acid (HPiv), 6-chloro-2-pyridonate [chp]−, NapCH2PO3H2, and NEt3.264 The core of this compound is similar to that found in decanuclear cobalt phosphonate complexes.265 Two symmetrical Ni5 motifs are connected to each other through the symmetrical bridging coordination action of the phosphonate and pivalate ligands. Each of the Ni5 subunits is formed by the bridging coordination of [F]−, [t-BuCO2]−, and [chp]− ligands. The peripheral part of the cage is stitched by pyridonate [chp]− and pivalate ligands (Figure 137). BS


Chemical Reviews

Review

Figure 146. Hexanuclear CuII phosphonates (a) [Cu6(C5H9PO3)4(phen)6(MeOH)4]·(ClO4)4;284 (b) [{Cu3(C5H9PO3)2(bipy)3(bipp)}(MeOH)2(H2O)(CH2Cl2)(ClO4)2]2282 (bipp = 4,4′-bipyridylpropane); and (c) [{Cu3(C5H9PO3)2(phen)3(bipp)(H2O)}(MeOH)(H2O)(ClO4)2]2.282

Reaction of [Ni 2(H 2O)(O 2CBu-t) 4 (HO 2CBu-t) 4 ] and PhPO3H2 afforded a dodecanuclear NiII phosphonate cluster, [Ni 12(μ 3-OH) 4(μ6 -O 3PC 6H 5 ) 4(μ2 -O 2CBu-t) 12(μ2 -L) 6 ] (L = HO2CMe/HO2CBu-t/H2O/MeCN). 263 This complex shows ε-Keggin159 type structural core. Three symmetrical Ni4 subunits are linked to each other through the phosphonate ligands. Each of the Ni4 subunits contains a single NiII center that is connected to a {Ni3(μ3-OH)} motif (Figure 138). Heterometallic dodecanuclear Ni/Ln phosphonates are known and have been prepared by utilizing the cluster expansion method. All of the reported dodecanuclear Ni/Ln phosphonates possess Well-Dawson type of core structures. Representative example are described here; the rest are summarized in Table 18. The reaction of [NiII2(μ-OH2)(O2CBu-t)4]·(HO2CBu-t)4, [Ln2(O2CBu-t)6(HO2CBu-t)6], and PhCH2PO3H2 afforded the dodecanuclear Ni/Ln cage [Ni II6 Gd III 6 (OH)2 (O 3PCH 2Ph) 6 (O 2 CBu-t) 16 (MeCO 2 H) 2 ](MeCN)4.20 This complex possesses a centrosymmetric rugbyball type of core structure (Figure 139). The two ends of the cage are capped by two {Ni3(μ3-OH)} triangular motifs. The edge of the triangle is bridged by pivalate and acetate

Figure 147. Decanuclear Cu II phosphonates, [Cu5 (μ3-OH)2 (t-BuPO3)3(2-PyPz)2(MeOH)]2·10MeOH·2H2O (2-PyPzH = 2-pyridylpyrazole).285

ligands. These two triangles are further connected to the GdIII ions through bridging phosphonate and three pivalate ligands. The Ni6Ln6P6 core of this complex resembles a BT


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Review

Figure 148. Dodecanuclear CuII phosphonates (a) Cu12(μ4-Cl)4(μ3-Cl)2(η1-3,5-Me2PzH)6(μ2-3,5-Me2PzH)4(μ3-O3PBu-t)(μ2-O3PBu-t)2(μ2HO3PBu-t)2;280 (b) [Cu12(μ-3,5-Me2Pz)8(η1-3,5-Me2PzH)2(μ4-O)2(μ3-OH)4(μ3-O3PBu-t)4]·3MeOH;286 and (c) [(Et3NH)2{Cu12(μ-3,5(CF3)2Pz)6(μ3-OH)6(μ-OH)3(μ3-O3PBu-t)2(μ6-O3PBu-t)3}{t-BuPO2(OH)}(C6H5CH3)2].286

Wells−Dawson type core that is well established in complexes such as [X2M18O62]n− [where X = P, Si, and As, M = Mo and W].265 A rare heterometallic NiII/UIII phosphonate complex, [H3O]4[Ni(H2O)3]4[Ni{(UO2)(PO3C6H4CO2)}3(PO4H)]4· 2.72H2O, was obtained in the reaction involving UO2(NO3)2· 6H2O, Ni(CH3COO)2·4H2O, diethyl(2-ethoxycarbonylphenyl) phosphonate, and HF (Figure 140).260

All molecular nickel phosphonates including heterometallic derivatives are summarized in Table 18.260−272 13.2. Palladium

PdII and PtII molecular phosphonates are very few. A mononuclear PdII phosphonate derivative, [(Dcp-OMe)PdAr2PC6H4PO2(OH)] (Dcp = dicyclopentadiene), was prepared in the reaction of [(Dcp-OMe)PdCl]2, 2-diphenylphosphinophenylphosphonic acid, Ar2PC6H4PO(OH)2 (Ar = BU


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Review

Figure 151. A tetranuclear Cu II phosphonate, [Cu 4 (L) 2 (C30H46P2O5)]·(PhCH3) [H3L = N,N′-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)], obtained in the reaction of [Cu2(L)(OAc)] with 2,4,6-i-Pr3C6H2PO3H2 and NEt3. The phosphonate anhydride ligand, [(2,4,6-i-Pr3−C6H2PO2)2O], is formed in situ.47 Adapted from ref 47. Copyright 2011 American Chemical Society. Figure 149. A hexadecanuclear CuII complex, [Cu8(Pz)4(μ3-OH)2(μ-OH) 2 (t-BuPO 3 ) 3 (CH 3 CO 2 ) 2 (CH 3 CN)] 2 ·(EtOAc) 2 (PzH = pyrazole).287

Figure 152. A hexanuclear CuII phosphonate, [Cu6(μ-bdmap)3(μ3PhPO3)2(μ3-OH)(μ3-O)(ClO4)2(H2O)]·5H2O.288 Adapted from ref 288. Copyright 2012 American Chemical Society.

central CuII ion surrounded by 12 PdII atoms (Figure 142). Other molecular palladium phosphonates are summarized in Table 19.273,274 13.3. Platinum

Information on all molecular PtII phosphonates is listed in Table 20.275−279 Ferrocenemonophosphonic and diphosphonic acids have been utilized to prepare mono- and dinuclear platinum phosphonate complexes.275 The reaction of ferrocenephosphonic acid and cis-[PtCl2(PPh3)2] in the presence of excess Ag2O afforded [FcCH2PO3Pt(PPh3)2]. In this compound, the phosphonate binds to the PtII center in a chelating manner (Figure 143a).275 A similar binding mode is observed in the reaction involving ferrocene diphosphonic acid, except that in this case a dinuclear complex, [1,1′-Fc′{PO3Pt(PPh3)2}2], is obtained (Figure 143b).275 Reaction of cis-[PtCl2L2] (L = PPh3), endo-8-camphanyl-phosphonic acid (C10H17PO3H2), and Ag2O also afforded a mononuclear PtII complex, [Pt(O3PC10H17)(PPh3)2]·2CHCl3, where the phosphonate also binds in a chelating manner.276 In all of these instances, the preference of the PtII center to have a square-planar coordination geometry

II

Figure 150. Tetranuclear Cu phosphonate, [Cu4(L)2(t-BuPO3)]· (CH3OH)2·(C6H6), obtained in the cluster expansion involving the reaction of [Cu2(L)(OAc)] [H3L = 1,3-bis(salicylideneamino)propan2-ol] with t-BuPO3H2 and Et3N.47 Adapted from ref 47. Copyright 2011 American Chemical Society.

Ph), and Na2CO3.273 The structure of this complex contains a monodentate phophonate ligand that is bound to the PdII center (Figure 141). Recently, Kortz et al. reported phenylphosphonate-capped polyoxopalladate complexes that encapsulate CuII or ZnII ions (Figure 142). Thus, the tridecanuclear heterometallic complex, Na6[CuIIO8PdII12(PhPO3)8]·35H2O, was prepared in the reaction of [Pd3(CH3CO2)6], PhPO3H2, Cu(CH3CO2)2·H2O, and NaOH.274 The molecular structure of this complex contains a BV


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Review

Figure 153. A molecular Cu18 phosphonate, [Cu18(4-Me-C6H4−PO3)8(Pz)12(μ2-OH)6(μ3-OH)2(H2O)2(Py)4]·2CH3CN·2H2O (Pz = pyrazolyl and Py = pyridine).289 Adapted from ref 289. Copyright 2013 American Chemical Society.

Figure 154. Hexaicosametallic core of [Cu26{2,3,5,6-(Me)4C6H− CH2−PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μ-OH2)2(OH2)2(MeCN)4]· 6MeCN·15H2O.49 Adapted from ref 49. Copyright 2013 The Royal Society of Chemistry.

Figure 155. Cu 24 Dy 8 core of [H 3 O][Cu 24 Dy 8 (Ph 3 CPO 3 ) 6 (Ph3CPO3H)6(MeCO2)12(MeCO2H)6(OH)42(NO3)(OH2)6].2 Adapted from ref 2. Copyright 2010 The Royal Society of Chemistry.

seems to dictate the outcome of the product formation along with coordination response of the phosphonate ligand.

particularly well-studied since 2000. The nuclearity of such molecular phosphonates varies from 1 to 26 in homometallic systems,49 while in the heterometallic complexes the highest nuclearity observed is 32.2 In the following sections, the synthesis and structure of various types of molecular CuII phosphonates will be described. Many of these Cu II phosphonates have also been studied in terms of their magnetic properties, and some of them have been investigated for their nuclease activity. A 2011 Dalton Transactions perspective deals with many molecular CuII phosphonates.281 These are not described again here. For continuity, however, representative examples are shown in Figures 144−149. Some recent examples, which have not been described in the Dalton Transactions perspective, are discussed below.

14. GROUP 11 PHOSPHONATES 14.1. Copper

The serendipitous isolation of a tetranuclear molecular CuII phosphonate cage, [Cu4Cl4(MePO3)2(3,5-Me2PzH)6], paved the way for the preparation molecular CuII phosphonate complexes by direct multicomponent approaches utilizing metal salts with phosphonic acids in the presence of ancillary ligands.58 A highlight of this approach has been the isolation of the dodecanuclear complex, Cu12(μ4-Cl)4(μ3-Cl)2(η1-3,5Me2PzH)6(μ2-3,5-Me2PzH)4(μ3-O3PBu-t)(μ2-O3PBu-t)2(μ2HO3PBu-t)2.280 Such molecular CuII phosphonates have been BW


BX

CuCl2, MeP(S)Cl2, 3,5-Me2PzH, benzene, NEt3, MePO3H2 Cu(OAc)2·H2O, Ph3CPO3H2 Cu(ClO4)2·6H2O, bpya, C5H9PO3H2, CuCl2, NEt3, NaClO4 C6H11PO3H2, CuCl2, bipy, KNO3, NEt3

CuSO4·5H2O, phen, NaOH, p-xylylenediphosphonic acid (H4L) CuSO4, Me4NOH, [ethane-1,2-diylbis(azanediyl)]bis[(4-chlorophenyl)methylene]diphosphonic acid (L1P), [ethane-1,2-diylbis(azanediyl)]bis[(4-bromophenyl)methylene]diphosphonic acid (L2P) Cu(ClO4)2·6H2O, bipy, C5H9PO3H2, NEt3 bpya, C5H9PO3H2, CuCl2, NEt3, NaClO4 Cu2(O2CMe)4·2H2O, t-BuPO3H2, 3,5-t-Bu2PzH, NEt3 2,4,6-i-Pr3C6H2PO3H2, 3,5-Me2PzH, Cu(CH3CO2)2·H2O

Cu(ClO4)2·6H2O, C3H7P(O)(OH)2, bpya, NEt3 Cu(ClO4)2·6H2O, CCl3P(O)(OH)2, bpya, NEt3 Cu(OAc)2·H2O, phen, 2-carboxyethyl(phenyl)phosphinic acid (H3L) 2,4,6-i-Pr3C6H2PO3H2, bipy, Cu(OAc)2·H2O 2,4,6-i-Pr3C6H2CH2PO3H2, 3,5-dimethyl pyrazole (3,5-Me2PzH), CuCl2, NaOH butylenediamine tetra(methylene phosphonic acid) (H8BDTMP), pyridine, Cu(OAc)2·H2O Cu(OAc)2·H2O, 2-C5H4NPO3H2 sodium alendronate trihydrate (4-amino-1-hydroxybutane-1,1-diylphosphonic acid sodium salt) (NaAle), CuCl2·2H2O phen, CuO, 1-amino-2-phenylethane-1,1-diphosphonic acid (APhEDPH4) CuSO4·5H2O, bipy, NaOH, p-xylylenediphosphonic acid (H4L)

Cu2(OAc)4·2H2O, N,N′-bis(phosphonomethyl)-1,10-diaza-18-crown-6 (H4L) CuCl2·2H2O, NaOH, HCl, hydroxyphosphonoacetic acid (HPAA), bipy CuCl2·2H2O, NaOH, HCl, hydroxyethylidene diphosphonic acid (HEDP), bipy CuCl2·2H2O, NaOH, HCl, pamidronic acid (PAM), bipy CuCl2·2H2O, NaOH, HCl, alendronic acid (ALE), bipy CuCl2·2H2O, NaOH, HCl, 1,2-ethanedisphosphonic acid (EDPA), bipy Na2[(CH2C5H5N)C(OH)(PO3H)2], Cu(NO3)2·5H2O CuSO4·5H2O, terpyridine (terpy), 1,2-bis(dimethoxyphosphoryl) benzene, HCl phen, PhPO3H2, Cu(OAc)2·H2O bipy, PhPO3H2, Cu(OAc)2·H2O phen, PhCH2PO3H2, Cu(OAc)2·H2O bipy, PhCH2PO3H2, Cu(OAc)2·H2O [(1,4,8,11-tetraazacyclotetradecan-1-yl)-methyl]phosphonic acid, (H2te1P), Cu(NO3)2·3H2O 4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (1,8-H4Me2te2p, H4L3), Cu (NO3)2·3H2O, NH4PF6 dimethanephosphonate pendant-armed cross-bridged cyclam (H2L·HCl·4H2O), CuCl2, NaOH 1,4,8,11-tetraazacyclotetradecane-1,8-di(methanephosphonic acid) (CB-TE2P), 1,4,8,11tetraazacyclotetradecane-1-(methanephosphonic acid)-8-(methanecarboxylic acid) (CB-TE1A1P), CuCl2, NaOH Cu(ClO4)2·6H2O, C5H9P(O)(OH)2, 2,2′- bipyridylamine (bpya), NEt3

reactants

Table 21. Molecular Copper Phosphonates

-do-dotrinuclear -dotetranuclear/D4R core tetranuclear/open-book tricyclic structure tetranuclear -do-do-do-

[Cu2(APhEDP)3(phen)2(H2O)2]·9H2O [Cu(H2O)(bipy)(H2L)]2·H4L·4H2O); [{Cu(H2O)(bipy) (H3L)}2(H2L)]·2H2O [Cu(H2O)(phen)(H2L)]2·6H2O Cu2(L1P)2, Cu2(L2P)2 [Cu3(C5H9PO3)2(bipy)3(MeOH)(H2O)]·(ClO4)2 [Cu3(C5H9PO3)2(μ-Cl)(bpya)3(H2O)]·(ClO4) [Cu2(3,5-t-Bu2PzH)2(t-BuPO3)2]2 [Cu4(μ3-OH)2{2,4,6-i-Pr3C6H2PO2(OH)}2(CH3CO2)2(3,5-Me2PzH)4] [CH3CO2]2·CH2Cl2 [Cu2Cl2(3,5-Me2PzH)3(MePO3)]2 [Cu4(OH)(Ph3CPO3)3(Ph3CPO2(OH) [Cu4(C5H9PO3)2(μ-Cl)2(bpya)4]·(Cl)2(CH3OH)2 [Cu4(μ-Cl)2(μ3-C6H11PO3)2(bipy)4]·(NO3)2

-do-do-

dinuclear/eightmembered ring -do-do-do-do-do-do-do-do-

[Cu2(μ2-C5H9PO3)2(bpya)2(H2O)2]·(H2O)4 [Cu2(μ2-C3H7PO3)2(bpya)2(H2O)2]·(H2O)2 [Cu2(μ2-CCl3PO3)2(bpy)2(MeOH)2]·(H2O) [Cu(L)(phen)(H2O)]2·3(H2O) [Cu2(2,4,6-i-Pr3C6H2PO3H)4(bipy)2] [Cu2(2,4,6-i-Pr3CH2C6H2PO3H)2(3,5-Me2PzH)2Cl2]·CH3OH [Cu2(H4BDTMP)(py)4]·2H2O [Cu(C5H4NPO3H)2]2 [Cu2(Ale)4(H2O)2]·2H2O

-do-do-

[CuL] Cu-CB-TE2P, Cu-CB-TE1A1P

nuclearity/structure mononuclear -do-do-do-do-do-do-do-do-do-do-do-do-do-

compounds Cu(H2L) [Cu(bipy)(HPAA)(H2O)]·H2O [Cu(bipy)(HEDP)(H2O)]·2H2O [Cu(bipy)(PAM)(Cl)(H2O)]·H2O [Cu(bipy)(ALE)(Cl)]·4H2O [Cu(bipy)(EDPA)(H2O)]2·3H2O [Cu{(CH2C5H5N)C(OH)(PO3H)2}2·4H2O] [Cu(terpy)(HO3PC6H4PO3H]·H2O [Cu(phen)2((OH)O2PC6H5)][(OH)O2PC6H5](H2O)7 [Cu((OH)O2PC6H5)2(bipy)] [Cu(phen)2((OH)O2PCH2C6H5)][(OH)O2PCH2C6H5](H2O)4 [Cu((OH)O2PCH2C6H5)2(bipy)(H2O)] trans-Br,O-[Cu(Br)(Hte1P)]·H2O [{Cu(H3L3)}{Cu(H2L3)}PF6·3H2O]

ref

58 45 282 283

282 282 35 194

299 300

268 299

187 187 212 188 188 298 58 250

187

296 297

290 291 291 291 291 291 251 292 293 293 293 293 294 295



reactants

BY

Na6[CuIIO8PdII12(PhPO3)8]·35H2O [Cu8(Pz)4(μ3-OH)2(μ-OH)2(t-BuPO3)3(CH3CO2)2(CH3CN)]2·(EtOAc)2 [Cu18(L)8(Pz)12(μ2-OH)6(μ3-OH)2(H2O)2(Py)4]·2CH3CN·2H2O

[Pd3(CH3CO2)6], PhPO3H2, Cu(CH3CO2)2·H2O, NaOH

Cu(NO3)2·3H2O, pyrazole, t-BuPO3H2, NEt3 Cu(NO3)2·2.5H2O, pyrazole, p-methylphenylphosphonic acid (LH2), pyridine, NEt3

Cu(ClO4)2·6H2O, t-BuPO3H2, 3,5-(CF3)2PzH, NEt3

CuCl2, t-BuPO3H2, 3,5-Me2PzH, NEt3

t-BuPO3H2, NEt3, Cu(NO3)2·3H2O, 3,5-dimethylpyrazole (3,5-Me2PzH)

pentanuclear hexanuclear -do-do-do-do-do-do-do-dononanuclear decanuclear -do-do-do-do-do-do-do-do-do-

[Cu3O4(SbAr)2(O3PBu-t)4(py)3] [Cu6(C5H9PO3)4(phen)6(MeOH)4]·(ClO4)4 [Cu6(C5H9PO3)4(phen)6(bipp)2]·(ClO4)4 [{Cu3(C5H9PO3)2(bipy)3(bipp)}(MeOH)2(H2O)(CH2Cl2)(ClO4)2]2 [{Cu3(C5H9PO3)2(bpya)3(4,4′-bpy)(H2O)}(MeOH)(H2O)(ClO4)2]2 [{Cu3(μ-i-PrPO3)2(bpy)3(4,4′-bpy)(H2O)}(H2O)2(ClO4)2]2 [Cu6(t-BuPO3)4(phen)6(4,4′-bipy)(MeOH)4]·(CH2Cl2)·(H2O)·(ClO4)4 [Cu6(μ-bdmap)3(μ3-O3PBu-t)2(μ3-OH)(μ3-O)(μ1,3-dca)(dca)(H2O)]·6H2O [Cu6(μ-bdmap)3(μ3-PhPO3)2(μ3-OH)(μ3-O)(ClO4)2(H2O)]·5H2O [Cu4O2(SbAr)2(O3PBu-t)2(O2CMe)2(OMe)6] [Cu5Li4O6(SbAr)4(O3PBu-t)6(O2CMe)2(OMe)4(MeOH)4] [Cu5(μ3-OH)2(t-BuPO3)3(2-PyPz)2(MeOH)]2·10MeOH·2H2O [Et3NH]4[Cu5(μ3-OH)2(O3PBu-t)3(PzH)2(t-BuPO3H)2]2·(solvent) [Cu5(μ3-OH)2(O3PBu-t)3(3-MePz)2(3-MePzH)2]2·(solvent) [Et3NH]4[Cu5(μ3-OH)2(O3PBu-t)3(3-MePz)2(t-BuPO3H)2]2·(solvent) [Et3NH]4[Cu5(μ3-OH)2(O3PBu-t)3(3-CF3−Pz)2(t-BuPO3H)2]2·(solvent) [Cu5(μ3-OH)2(O3PBu-t)3(3-PhPz)2(3-PhPzH)2]2·(solvent) [Cu5(μ3-OH)2(O3PBu-t)3{3-(2-PyPz)}2(MeOH)]2·(solvent) [Cu5(μ3-OH)2(O3PBu-t)3(3−2-PyPz)2]2·(solvent) [Cu5(μ3-OH)2(O3PBu-t)3(3−2-PyPz)2(H2O)2]2·(Et3NH·PF6)2(solvent) [Cu5(μ3-OH)2(O3PBu-t)3(3−2-MeO−C6H4Pz)2(MeOH)2]2·(0.5:0.5MeOH/ H2O) [Cu8O4(SbAr)2(O3PBu-t)6(O2CMe)4(lutidine)2]

dodecanuclear/barrelshaped architecture dodecanuclear/crownshaped architecture heterometallic tridecanuclear hexadecanuclear octadecanuclear

heterometallic decanuclear dodecanuclear

-do-do-do-do-

[Cu4(L)2(μ-C5H9PO3)]·(CH3OH)2 [Cu4(L)2(t-BuPO3)]·(CH3OH)2·(C6H6) [Cu4(L)2(PhPO3)(H2O)2(NMe2CHO)]·(H2O)2 [Cu4(L)2(μ-C6H11PO3)]·(MeOH)4·(H2O)2

nuclearity/structure -do-do-do-do-do-

compounds [Cu4(μ-CH3CO2)2(μ3-C6H11PO3)2(bipy)4]·(CH3CO2)2 [Cu4(μ-OH)(μ3-C6H11PO3)2(bipy)4(H2O)2]·(NO3)3 [Cu4(μ-OH)(μ3-C6H11PO3)2(phen)4(H2O)2](NO3)3 [Cu4(Hmbpp)2(H2NC(O)NH2)2(H2O)8]·4H2O [Cu4(L)2(2,4,6-i-Pr3C6H2PO2)2O)]·(PhCH3)

[Cu12(μ4-Cl)4(μ3-Cl)2(η1-3,5-Me2PzH)6(μ2-3,5-Me2PzH)4(μ3-O3PBu-t)(μ2O3PBu-t)2(μ2-HO3PBu-t)2] [Et3NH]2[Cu12(μ-3,5-(CF3)2Pz)6(μ3-OH)6(μ-OH)3(μ3-O3PBu-t)2(μ6-O3PBut)3][t-BuPO2(OH)][C6H5CH3]2 [Cu12(μ-DMPz)8(η1-3,5-Me2PzH)2(μ4-O)2(μ3-OH)4(μ3-O3PBu-t)4]·3MeOH

p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, LiOMe, t-BuPO3H2, lutidine

C6H11PO3H2, bipy, NEt3, Cu(OAc)2·H2O C6H11PO3H2, Cu(NO3)2·3H2O, bipy, NEt3 C6H11PO3H2, NEt3, Cu(NO3)2·3H2O, phen 4-methyl-2,6- bis(phosphonomethyl)phenol (H5mbpp), urea, NaOH, Cu(ClO4)2·6H2O 1,3-bis(salicylideneamino)propan-2-ol (H3L), 1,3-bis(4,5-dimethylsalicylideneamino)propan-2-ol (H3L), Cu (OAc)2·2H2O, NEt3, 2,4,6-i-Pr3C6H2 PO3H2 1,3-bis(4,5-dimethylsalicylideneamino)propan-2-ol (H3L), Cu(OAc)2·2H2O, NEt3, C5H9PO3H2 1,3-bis(salicylideneamino)propan-2-ol (H3L), t-BuPO3H2, NEt3, Cu(OAc)2·2H2O, [Cu2(L)(OAc)] 1,3-bis(salicylideneamino)propan-2-ol (H3L), Cu(OAc)2·2H2O, PhPO3H2, NEt3, [Cu2(L)(OAc)] 1,3-bis(4,5-dimethylsalicylideneamino)propan-2-ol (H3L), Cu(OAc)2·2H2O, C6H11PO3H2, NEt3, [Cu2(L) (OAc)] p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, LiOMe, t-BuPO3H2, pyridine Cu(ClO4)2·6H2O, C5H9PO3H2, NEt3, phen Cu(ClO4)2·6H2O, C5H9PO3H2, NEt3, phen, bipp Cu(ClO4)2·6H2O, bipy, C5H9PO3H2, NEt3, 1,3-bis(4-pyridyl)propane (bipp) Cu(ClO4)2·6H2O, bpya, C5H9PO3H2, NEt3, 4,4′-bipyridine, i-PrPO3H2 Cu(ClO4)2·6H2O, bpya, NEt3, 4,4′-bipyridine, i-PrPO3H2 Cu(ClO4)2·6H2O, phen, t-BuPO3H2, NEt3, 4,4′-bipyridine t-BuPO3H2, 1,3-bis(dimethylamino)-2-propanol (Hbdmap), Cu(OH)2, NaN(CN)2 PhPO3H2, 1,3-bis(dimethylamino)-2-propanol (Hbdmap), Cu(ClO4)2·6H2O, NaOH p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, LiOMe, t-BuPO3H2 p-chlorophenylstibonic acid (ArSbO3H2), Cu(OAc)2·4H2O, LiOMe, t-BuPO3H2 Cu(ClO4)2·6H2O, 2-PyPzH, t-BuPO3H2, NEt3 t-BuPO3H2, Cu(SO3CF3)2, pyrazole, Et3N t-BuPO3H2, Cu(ClO4)2·6H2O, 3-methylpyrazole, Et3N t-BuPO3H2, CuCl2, 3-methylpyrazole, Et3N t-BuPO3H2, CuCl2, 3-CF3PzH, Et3N t-BuPO3H2, CuCl2, 3-PhPzH, Et3N t-BuPO3H2, Cu(ClO4)2·6H2O, 3-(2-Py)PzH, Et3N t-BuPO3H2, Et3N, [Cu(O2CMe)(3-(2-Py)-Pz)]n t-BuPO3H2, KPF6, CuCl2, 3-(2-Py)PzH, Et3N t-BuPO3H2, Cu(ClO4)2·6H2O, 3-(2-MeO-C6H4)-PzH, Et3N

Table 21. continued ref

287 289

273

286

286

280

117

117 45 284 282 282 282 282 288 288 117 117 285 302 302 302 302 302 302 302 302 302

47 47 47 47

283 283 283 301 47



49

2 2

2

hexaicosanuclear

octaicosanuclear dotriacontanuclear

-do-

nuclearity/structure compounds

Review

[Cu26{2,3,5,6-(Me)4C6H−CH2−PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μOH2)2(OH2)2(MeCN)4]·6MeCN·15H2O [Me4N]3[Cu16Y12(Ph3CPO3)12(MeCO2)22(OH)24(NO3)2(OH2)6] [OH] [H3O][Cu24Dy8(Ph3CPO3)6(Ph3CPO3H)6 (MeCO2)12(MeCO2H)6(OH)42(NO3)(OH2)6] [(Me4N)2K2] [Cu24Gd8(Ph3CPO3)6(Ph3CPO3H)6(MeCO2)12(MeCO2H)12(OH)42(NO3)] [(OH)3]

ref

Chemical Reviews

Figure 156. A tetracoordinate AgI phosphonate, [Ag(ampa)2NO3] (ampa = aminomethylphosphonic acid).303 Adapted from ref 303. Copyright 2008 Elsevier Masson SAS.

Recently, we have synthesized a tetranuclear CuII ensemble, [Cu4(L)2(t-BuPO3)]·(CH3OH)2·(C6H6), utilizing a cluster expansion strategy, as follows.47 The reaction of Cu(OAc)2· 2H2O with 1,3-bis(salicylideneamino) propan-2-ol (H3L) afforded a dinuclear derivative, [Cu2(L)(OAc)]. The labile carboxylate ligand of the latter was replaced by a phosphonate, affording the tetranuclear CuII phosphonate (Figure 150). In a slight variation, a condensed phosphonate anyhdride also enables the bridging of two such subunits to result in the tetranuclear ensemble, [Cu4(L)2(C30H46P2O5)]·(PhCH3) [H3L = N,N′-(2-hydroxypropane-1,3-diyl)bis(4,5-dimethylsalicylaldimine)] (Figure 151).47 An in situ, one-pot reaction involving Cu(ClO4)2·6H2O, PhPO3H2, 1,3-bis(dimethylamino)-2-propanol (Hbdmap), and NaOH afforded a hexanuclear CuII phosphonate, [Cu6(μbdmap)3(μ3-PhPO3)2(μ3-OH)(μ3-O)(ClO4)2(H2O)]·5H2O,288 which possesses two trimeric Cu3O subunits. Each of the trinuclear motifs is capped by a 3.111 coordination mode of the [PhPO3]2− ligands. The two trinuclear units are held together by [bdmap]− and [ClO4]− ligands (Figure 152). A nanosized cage, octadecameric CuII phosphonate complex, [Cu18(4-Me-C6H4−PO3)8(Pz)12(μ2-OH)6(μ3-OH)2(H2O)2(Py)4]· 2CH3CN·2H2O (Pz = pyrazolyl and Py = pyridine), was synthesized in the reaction of Cu(NO3)2·2.5H2O, pyrazole,

Gd(NO3)3·xH2O (Ln = Dy, Gd, Y), Cu(OAc)2·H2O, Ph3CPO3H2, Me3N

Y(NO3)3·xH2O (Ln = Dy, Gd, Y), Cu(OAc)2·H2O, Ph3CPO3H2, Me3N Dy(NO3)3·xH2O, Cu(OAc)2·H2O, Ph3CPO3H2, Me3N

2,3,5,6-Me4C6HCH2−PO3H2, Et3N, CuCl2

Table 21. continued

reactants

Figure 157. An octanuclear AgI phosphonate, [Ag8(dppm)4(tBuPO3)2(ClO4)(NO3)0.67(H2O)1.33]·(ClO4)2.33·(CH3OH)6.67 (dppm = bis(diphenylphosphino)ethane).304 Adapted from ref 304. Copyright 2013 The Royal Society of Chemistry.

BZ


Chemical Reviews

Review

structure is held together by the multiple coordination action of 18[RPO3]2−, 10[OH]−, 6[Cl]−, and 2[H2O] ligands (Figure 154). A heterometallic Cu24Dy8 phosphonate cage, [H3O][Cu24Dy8(Ph3CPO3)6(Ph3CPO3H)6(MeCO2)12(MeCO2H)6(OH) 42 (NO 3)(OH 2 ) 6 ] 2, was prepared by utilizing the sterically bulky phosphonic acid, Ph3CPO3H2. The structure of this complex consists of three motifs. A central part contains 16 CuII ions, which is surrounded by 8 DyIII ions. The final layer contains eight more CuII centers. The connection between these various units is achieved by the phosphonate, carboxylate, and hydroxide ligands (Figure 155). The details on all of the copper phosphonates are listed in Table 21. 14.2. Silver and Gold

There are no reports on molecular gold phosphonate complexes. Molecular AgI phosphonates are very few. Most of these are heterometallic complexes where the nuclearity varies from 1 to 61.303−307 The mononuclear AgI phosphonate, [Ag(ampa)2NO3],303 was obtained in the reaction of AgNO3 with ampa (ampa = aminomethylphosphonic acid). In this complex, a tetracoordinate AgI is bound by a chelating nitrate ligand along with two monodentate phosphonate ligands (Figure 156). The reaction of PhCCAg, AgClO4, t-BuPO3H2, and bis(diphenylphosphino)ethane (dppm) afforded an octanuclear molecular AgI phosphonate cluster, [Ag8(dppm)4(t-BuPO3)2(ClO4)(NO3)0.67(H2O)1.33]·(ClO4)2.33·(CH3OH)6.67.304 The latter contains two linear Ag4 subunits. Each Ag4 motif is coordinated by two bridging dppm ligands. Two of these Ag4(dppm)2 units are connected to each other by two [t-BuPO3]2−, a [ClO4]−, a [NO3]−, and two water molecules (Figure 157). Utilizing the same strategy, a homonuclear Ag22 phosphonate, [{Ag8(Cl@Ag14)}(t-BuCC)14(t-BuPO3)2F2(H2O)2]·BF4· 3.5H2O, was prepared in a reaction involving AgCCBu-t, t-BuPO3H2, and AgBF4 in the presence of Me4NCl.305 The skeleton of this cluster contains a rhombic-dodecahedral Ag14

Figure 158. A molecular Ag22 phosphonate, [{Ag8(Cl@Ag14)}(tBuCC)14(t-BuPO3)2F2(H2O)2]·BF4·3.5H2O.305 Adapted from ref 305. Copyright 2012 American Chemical Society.

p-methylphenylphosphonic acid (LH2), pyridine, and NEt3.289 The core of this molecule is chair-shaped and contains two Cu9 motifs, which are connected to each other through the bridging phosphonate ligands in a 4.211 coordination mode (Figure 153). Recently, we have isolated a hexaicosametallic copper(II) phosphonate cage, [Cu26{2,3,5,6-(Me)4C6H−CH2−PO3}18(μ2-OH)4(μ3-OH)6(μ4-Cl)6(μ-OH2)2(OH2)2(MeCN)4]·6MeCN· 15H2O in the reaction of CuCl2 and 2,3,5,6-Me4C6HCH2− PO3H2 (RPO3H2) in the presence of Et3N.49 The cage

Figure 159. An Ag28 phosphonate, [{Ag5(NO3@Ag18)Ag5}(t-BuCC)16(t-BuPO3)4(H2O)3], with an encapsulated nitrate.305 Adapted from ref 305. Copyright 2012 Springer Science. CA


Chemical Reviews

Review

Figure 160. A cashew-nut-shaped heterometallic Ag21V7 phosphonate complex, [Cl2@Ag21(CCBu-t)9{(t-BuPO3)3VV3O6(OH)}2{(t-BuPO3)VVO2(OH)}(MeOH)2(H2O)2]·2MeOH·2H2O.167 Adapted from ref 167. Copyright 2012 Wiley-VCH Verlag GmbH & Co. KGaA.

Table 22. Molecular Silver Phosphonates reactants aminomethylphosphonic acid (ampa), AgNO3 PhCCAg, AgClO4, t-BuPO3H2, bis(diphenylphosphino) ethane (dppm) AgCCBu-t, t-BuPO3H2, AgBF4 AgCCPh, t-BuPO3H2, (Et4N)VO3, AgNO3 AgCCBu-t, t-BuPO3H2, (Et4N)VO3, AgNO3 (Me4N)3(H3V10O28), AgCCPh, AgNO3, t-BuPO3H2, dimethylformamide (DMF) AgCCBu-t, t-BuPO3H2, AgBF4 (Et4N)VO3, t-BuPO3H2, AgCCBu-t, AgBF4, (BzEt3N)Cl, aqueous H2O2 AgCCBu-t, (NH4)4[V2O4(D,L-citrate)2]· 4H2O (Et4N)VO3, t-BuPO3H2, AgCCBu-t, (BzEt3N)Cl, aqueous H2O2, AgBF4, 2-chloropyridine (2-PyCl) (Et4N)VO3, t-BuPO3H2, AgCCBu-t, (BzEt3N)Cl, aqueous H2O2, AgBF4 (Me4N)3(H3V10O28), AgCCPh, AgNO3, t-BuPO3H2, dimethylformamide (DMF), H2O2 (30%), Ph2PCH2PPh2

compounds


ref

[Ag(ampa)2NO3] {Ag8(dppm)4(t-BuPO3)2(ClO4)(NO3)0.67(H2O)1.33}·(ClO4)2.33·(CH3OH)6.67

mononuclear octanuclear

303 304

[{Ag8(Cl@Ag14)}(t-BuCC)14(t-BuPO3)2F2(H2O)2]·BF4·3.5H2O [(NO3)2@Ag16(CCPh)4{(t-BuPO3)4V4O8}2(DEF)6(NO3)2] [(NO3)2@Ag16(CCBu-t)4{(t-BuPO3)4V4O8}2(DMF)6(NO3)2]·DMF·2H2O; [(NO3)2@ Ag16(CCBu-t)4{(t-BuPO3)4V4O8}2(DMF)6(NO3)2}·{(NO3)2@Ag16(CCBu-t)4 {(t-BuPO3)4V4O8}2(DMF)4(py)2(NO3)2}·DMF·5H2O [(NO3)2@Ag16(CCPh)4{(t-BuPO3)4V4O8}2(DMF)6(NO3)2]·DMF·H2O

-dotetraicosanuclear -do-

305 306 306

-do-

307

[{Ag5(NO3@Ag18)Ag5}(t-BuCC)16(t-BuPO3)4(H2O)3]; [{Ag5(NO3@Ag18)Ag5} (t-BuCC)16(t-BuPO3)4(H2O)4]·3SiF6·4.5H2O·3.5MeOH [Cl2@Ag21(CCBu-t)9{(t-BuPO3)3V3O6(OH)}2{(t-BuPO3)VO2(OH)} (MeOH)2(H2O)2]·2MeOH·2H2O; [Cl2@Ag21(CCBu-t)9{(t-BuPO3)3V3O6(OH)}2 {(t-BuPO3)VO2(OH)}(MeOH)2(H2O)2]·2MeOH·2H2O [(VO4)2@Ag34(CCBu-t)22(NO3)6]·8H2O

octaicosanuclear

305

octaicosanuclear/ cashew-nut-shaped

167

hexatriaconta nuclear

306

[(Et)4N+]3[{(O2)V2O6}2@Ag36(CCBu-t)12{(t-BuPO3)4V4O8}2(t-BuPO3)2(NO3)7 (2-PyCl)(DMF)]

octatetraconta nuclear/ cashew-nut-shaped

167

[(Et)4N+]2[{(O2)V2O6}2Cl@Ag36(CCBu-t)11{(t-BuPO3)4V4O8}2{(t-BuPO3)2(VO2)} (t-BuPO3)2 (t-BuPO3H)(DMF)(NO3)2(Et2O)(H2O)3]·2DMF·2Et2O·4H2O [{(O2)V2O6}3@Ag43(CCPh)19{(t-BuPO3)4V4O8}3(DMF)6]·5DMF·2H2O

nonatetraconta nuclear/ cashew-nut-shaped monohexacontanuclear

167 307

is shown in Figure 160. This complex is centrosymmetric and has a cashew-nut-shaped structure and encapsulates a pair of templating chloride ions.167 All molecular silver phosphonates are listed in Table 22.167,303−307

motif that encapsulates a chloride ligand along with a Ag8 motif that has a square-face Archimedean antiprism. These two subunits are connected by two tert-butylphosphonate ligands (Figure 158). A homometallic molecular Ag28 phosphonate complex, [{Ag 5 (NO 3 @Ag 18 )Ag 5 }(t-BuCC) 16 (t-BuPO 3 ) 4 (H 2 O) 3 ][{Ag 5 (NO 3 @Ag 18 )Ag 5 }(t-BuCC) 16 (t-BuPO 3 ) 4 (H 2 O) 4 ]· 3SiF6·4.5H2O·3.5MeOH, could be obtained in the reaction of AgCCBu-t, t-BuPO3H2, and AgBF4.305 The cluster encapsulates a nitrate ion. The latter may be functioning as a template for enabling the assembly of the cage (Figure 159). Several heterometallic AgI/VV phosphonates of varying nuclearities, Ag16V8, Ag21V7, Ag34V12, Ag34V13, and Ag43V18, are known.167,303−307 A representative heterometallic Ag21V7 phosphonate, {Cl2@Ag21(CCBu-t)9[(t-BuPO3)3VV3O6(OH)]2[(t-BuPO 3 )VV O 2 (OH)]MeOH)2 (H 2 O) 2 }·2MeOH ·2H 2 O,

15. GROUP 12 PHOSPHONATES 15.1. Zinc

The nuclearity of homometallic ZnII phosphonates varies between 1 and 12,308 while the highest nuclearity achieved in the heterometallic system is 13.274 A representative mononuclear ZnII phosphonate, Zn(hedpH2)3·3NH2(CH3)2NH(CH3)3·3H2O,211 is shown in Figure 161. This compound was prepared by the reaction of Zn(OAc)2·2H2O and 1-hydroxyethylidenediphosphonate acid (hedpH4) under hydrothermal conditions. The molecular CB


Chemical Reviews

Review

Figure 163. A planar tetranuclear ZnII phosphonate, [{(ZnMe)4(THF)2}{t-BuPO3}2].309 Adapted from ref 309. Copyright 2004 The Royal Society of Chemistry.

Figure 161. A mononuclear ZnII phosphonate, Zn(hedpH2)3· 3NH2(CH3)2NH(CH3)3·3H2O, complex.211 Adapted from ref 211. Copyright 2013 The Royal Society of Chemistry.

Scheme 62. Synthesis of a Dinuclear ZnII Phosphonate, (HNEt3)2{Zn2(η1-3,5-Me2PzH)2Cl2(Cl3CPO3)2}244

Figure 164. A tetranuclear ZnII phosphonate complex, [t-BuPO3Zn(2apy)]4, possessing a D4R core (2-apy = 2-aminopyridine).220,310 Adapted from ref 310. Copyright 2007 The Royal Society of Chemistry.

satisfy the coordination needs of the ZnII. Several such dinuclear ensembles, involving other metal ions, have been discussed above. An interesting trinuclear ZnII phosphonate, [Zn3Cl2(3,5Me2Pz)4(t-BuPO3)2], was obtained in the reaction of ZnCl2, tBuPO3H2, 3,5-Me2PzH, and NEt3. The three zinc centers present in a plane are held together by two bicapping tridentate [t-BuPO3]2− ligands (Figure 162).192 Tetranuclear ZnII phosphonates possessing various types of structures such as D4R,220 open-book tricyclic,63 etc., are known. Roesky et al. have prepared a tetranuclear ZnII phosphonate cage, [{(ZnMe)4(THF)2}{t-BuPO3}2], in a reaction involving ZnMe2 and t-BuPO3H2.309 In this compound, the four ZnII atoms are arranged in a planar arrangement and are capped on the top and below by capping phosphonate ligands that bind in a 4.211 coordination mode. Each pair of ZnII ions are connected by a THF molecule (Figure 163). A tetranuclear ZnII phosphonate complex, [t-BuPO3Zn(2-apy)]4 (2-apy = 2-aminopyridine), possessing a D4R core structure has been synthesized in the reaction of Zn(OAc)2· 2H2O, 2-aminopyridine, and t-BuPO3H2.220,310 The molecular structure contains a core that is a distorted cube, alternate corners of which are occupied by ZnII and phosphorus; the

Figure 162. A planar trinuclear ZnII phosphonate, [Zn3Cl2(3,5Me2Pz)4(t-BuPO3)2].192 The three ZnII ions are held together by two tricapping [t-BuPO3]2− ligands. Adapted from ref 192. Copyright 2002 American Chemical Society.

structure of this compound reveals an octahedral environment around ZnII; all six positions are occupied by the oxygen atoms emanating from the diphosphonate, [hedpH2]− ligand. Several dinuclear Zn II phosphonates are known. A representative dinuclear ZnII phosphonate is described. (HNEt3)2{Zn2(η1-3,5-Me2PzH)2Cl2(Cl3CPO3)2} has been synthesized in a multicomponent reaction involving ZnCl2, CCl3PO3H2, and 3,5-dimethylpyrazole in the presence of NEt3 (Scheme 62).244 The molecular structure of this compound reveals a central eight-membered puckered ring. The phosphonate ligands bridge the two ZnII ions, while the pyrazole and chloride ligands function as terminal ligands to CC


Chemical Reviews

Review

Scheme 64. Synthesis of [Zn4(FMPA)4(phen)4]·7CH3OH311

Scheme 63. Synthesis of the Tetranuclear ZnII Phosphonate, [Zn4(ArPO3)2{(ArP(O)2(OH)}2(3,5-Me2PzH)4(3,5Me2Pz)2]·5MeOH, That Possesses an Open-Book Type of Core194

one ethyl group. The molecular structure of this compound contains two nonidentical Zn3 subunits that are fused to each other through three [t-BuPO3]2− ligands. One of these units is held by the 3.111 binding coordination of the [t-BuPO3]2− ligand, while the other does not have binding from the phosphonate. On the other hand, it is held by a μ3-OEt ligand (Figure 165). The remaining hexanuclear ZnII phosphonates are summarized in Table 23. A cylindrical drum-shaped heptanuclear ZnII phosphonate, [Zn7{(2-C5H4N)CH(OH)PO3}6(H2O)6]SO4·4H2O, was obtained in the direct reaction of ZnSO4·7H2O, 2-C5H4NCH(OH)PO3H2 [hydroxy(2-pyridyl)methylphosphonic acid], and NaOH under hydrothermal conditions.312 The structure of this compound reveals the presence of a central ZnII ion that is encapsulated by two Zn3 subunits. Each of the Zn3 units is built by the coordination of the bridging phosphonate ligands. The latter along with other ligands also connect the two trimeric units together (Figure 166). The reaction of Zn(CH3CO2)2, H3L [H3L = 1-C10H7− CH2N(CH2CO2H)(CH2PO3H2)], and NEt3 under hydrothermal conditions afforded a heptanuclear compound, (HN(C2H5)3)4[Zn7(L)6]·2H2O,313 where six of the ZnII ions occupy the corners of an octahedron, while the seventh ZnII lies in the center (Figure 167). An octanuclear ZnII phosphonate cage, [Zn8(Cl)6{2,3,5,6(Me) 4 C 6 HCH 2 PO 3 } 6 (Et 3 N) 2 (Et 3 NH) 2 ]·2n-hexane·3H 2 O, was synthesized in a multicomponent reaction involving anhydrous ZnCl 2 , (Me) 4 C 6 HCH 2 PO 3 H 2 , and NEt 3 . 314 The structure of this compound reveals that the eight Zn(II) ions that are held together by six [2,3,5,6-(Me)4C 6 HCH 2 PO 3 ] 2− ligands. The Zn 8 P 6 O 18 core of this compound has an ellipsoid-shaped type core structure, which contains six symmetry-related eight-membered Zn2P2O4 rings. Six of the ZnII ions have a terminal chloride ligand, while the other two ZnII ions are bound to neutral triethylamine ligands (Figure 168). The reaction of Zn(CH3CO2)2, with H3L [H3L = 1-C10H7− CH2N(CH2CO2H)(CH2PO3H2)], under hydrothermal conditions afforded a nonanuclear ZnII phosphonate cluster [Zn9(L)6(H2N(CH2)2NH(CH2)2NH(CH2)2NH2)2]·18H2O.313

oxygen atoms of the phosphonate ligand occupy the edges of the cube (Figure 164). We have prepared a tetranuclear ZnII phosphonate possessing an open-book type of core.194 The reaction of the sterically bulky phosphonic acid, 2,4,6-i-Pr3−C6H2−PO3H2 (ArPO3H2), with Zn(CH3CO2)2·2H2O and 3,5-Me2PzH afforded the tetranuclear ZnII phosphonate, [Zn4(ArPO3)2{(ArP(O) 2 (OH)} 2 (3,5-Me 2 PzH) 4 (3,5-Me 2 Pz) 2 ]·5MeOH (Scheme 63). The molecular structure of this compound possesses an open-book type conformation containing three interconnected Zn 2 P 2 O 4 eight-membered rings. Two [ArPO3]2− ligands hold the central portion of the molecule, while two other [ArP(O)2(OH)]− ligands hold the terminal portion of the complex. The terminal zinc atoms possess two pyrazole ligands, while the central zinc atoms contain one pyrazole ligand each. The reaction of ZnSO 4 ·7H 2O, FcCH 2PO 3H 2 (Fc = ferrocenyl), phen, and NEt3 afforded [Zn4(FMPA)4(phen)4]· 7CH3OH [FMPA = FcCH2PO3H2).311 The centrosymmetric tetrameric core of this complex contains four ZnII ions that are connected to each other by bridging [FcCH2PO3]2− ligands (Scheme 64). Other tetranuclear ZnII phosphonates are tabulated (Table 23). Although pentanuclear ZnII phosphonates are unknown, several hexanuclear derivatives are known. Thus, the reaction of ZnCl2, 3,5-Me2PzH, PhPO3H2, and NEt3 afforded a hexanuclear ZnII phosphonate, [Zn6Cl4(3,5-Me2PzH)8(PhPO3)4] (Scheme 65).192 The six zinc atoms are arranged in a chairshaped core structure where two trinuclear motifs are connected to each other through the bridging action of four [PhPO3]2− ligands (3.111 coordination mode). The structure contains a central tricyclic unit containing four ZnII centers, which are connected on either side to a ZnII each. Another hexanuclear ZnII phosphonate cage, [{(ZnEt)3(Zn(THF))3}{t-BuPO3}4{3-OEt}], was obtained in the reaction of t-BuPO3H2 and ZnEt2.309 In this compound, three zinc atoms are fully dealkylated, while the other three contain CD


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Review

Table 23. Molecular Zinc Phosphonates reactants Zn(OAc)2·2H2O, 1−1-hydroxyethylidenediphosphonie acid (hedpH5) 1,4,8,11-tetraazacyclotetradecane-1,8-bis (methylphosphonic acid) (H4L), Zn(OAc)2·2H2O ZnCl2, N-(phosphonomethyl) iminodiacetic acid (H4PMIDA), NH4F ZnCl2, CCl3PO3H2, 3,5-dimethyl-1H-pyrazole (3,5-Me2PzH), NEt3 3,5-di-tert-butyl-2-hydroxybenzylphosphonic acid (dtbhpH2), tetramethylenethylene diamine (TMEDA), Zn(OAc)2·2H2O [O3PCH(Ph)NH(CH2)2NHCH(Ph)PO3] (eddbp), Zn(NO3)2·6H2O 4-pyridylthioethylphosphonic acid hydrobromide (H2pytep· HBr), Zn(NO3)2·6H2O imidazole (Im), 1-amino-1-phenylmethane-1,1-diphosphonic acid (APhMDPH4), phen, ZnO [O3PCH(Ph)NH(CH2)2NHCH(Ph)PO3] (eddbp), Zn(NO3)2·6H2O Zn(ClO4)2·6H2O, pyrazole (PzH), CCl3PO3H2, NEt3 ZnCl2, t-BuPO3H2, 3,5-Me2PzH, NEt3 t-BuPO3H2, Zn(OAc)2·4H2O, 2-pyridylamine (2-apy)

compounds

211

trans-O,O-[Zn(H2L)]

-do-

213

(NH4)[Zn(PMIDA)(H2O)2]

-do-

315

[{Zn2(η1-3,5-Me2PzH)4(Cl3CPO3)2}{Zn(η1-3,5Me2PzH)2(Cl)2}2]·(toluene)2; {Zn2(η1-3,5Me2PzH)2(Cl)2(Cl3CPO3)2}(HNEt3)2 [Zn2(dtbhp)2(TMEDA)2(H2O)2]·0.5CH3CN

dinuclear

315

-do-

321

[NH3CH(CH3)CH2NH3]2Zn2(edbbp)2(HNO3)2·4H2O

-do-

316

[Zn2(pytepH2)2Br4]

-do-

317

[Zn2(APhMDP)(phen)4]·12H2O

-do-

268

[NH3CH(CH3)CH2NH3]2Zn2(edbbp)2·H2O

-do-

318

[{(ZnCl)2(η2-Pz)2(Cl3CPO3)}(Et3NH)2 [Zn3Cl2(3,5-Me2Pz)4(t-BuPO3)2] [t-BuPO3Zn(2-apy)]4

-dotrinuclear tetranuclear/D4R core -dotetranuclear/openbook tricyclic structure tetranuclear -do-dohexanuclear/chairlike structure hexanuclear -do-do-

314 192 220

[t-BuPO3Zn(2-apy)]4 [Zn4(ArPO3)2{(ArP(O)2(OH)}2(3,5-Me2PzH)4(3,5-Me2Pz)2]· 5MeOH

ZnMe2, t-BuPO3H2 Zn(ClO4)2·6H2O, 3,5-Me2PzH, CCl3PO3H2, NEt3 ZnSO4·7H2O, FcCH2PO3H2 (FMPAH2), phen, NEt3 ZnCl2, 3,5-Me2PzH, PhPO3H2, NEt3

[{(ZnMe)4(THF)2}{t-BuPO3}2] [{Zn4(η1-DMPzH)6(Cl3CPO3)2}(μ-OH)2(ClO4)2] [Zn4(FMPA)4(phen)4]·7CH3OH [Zn6Cl4(3,5-Me2PzH)8(PhPO3)4]

t-BuPO3H2, ZnEt2 MeN(CH2CO2H)(CH2PO3H2)(H3L), Zn(CH3CO2)2·2H2O (m-HO3S−PhO3H2), phen, NaOH, ZnCO3

[{(ZnEt)3(Zn(THF))3}{t-BuPO3}4{3-OEt}] {Zn6L6(Zn)}{Zn(H2O)6}2·22H2O [Zn(phen)3]2[Zn4(m-O3S-PhPO3)4(phen)4]·20H2O; [Zn6(m-O3S-PhPO3)4(phen)8]·11H2O [Zn6(m-O3S-PhPO3)4(bipy)6(H2O)4]·18H2O [Zn7{(2-C5H4N)CH(OH)PO3}6(H2O)6]SO4·4H2O

Zn(CH3CO2)2, [H3L = 1-C10H7−CH2N(CH2CO2H) (CH2PO3H2)], hydrothermal anhydrous ZnCl2, NEt3, (Me)4C6HCH2PO3H2 Zn(CH3CO2)2, 1-C10H7−CH2N(CH2CO2H)(CH2PO3H2) (H3L), hydrothermal H2O3PCH2NC5H9CO2H (H3L), Zn(NO3)2·6H2O, phen, Me4NOH H2O3PCH2NC5H9CO2H (H3L), Zn(NO3)2·6H2O, Me4NOH, bipy H2O3PCH2NC5H9CO2H (H3L), Zn(NO3)2·6H2O, Me4NOH t-BuPO3H2, ZnEt2 [Pd3(CH3CO2)6], ZnCl2, NaOH, PhPO3H2

ref

mononuclear

Zn(OAc)2·2H2O, 2-aminopyridine (2-apy), t-BuPO3H2 2,4,6-triisopropylphenylphosponic acid [ArP(O)(OH)2], 3,5Me2PzH, Zn(OAc)2·2H2O

(m-HO3S−PhO3H2), bipy, NaOH, ZnCO3 ZnSO4·7H2O, NaOH, hydroxy(2-pyridyl)methylphosphonic acid


Zn(hedpH2)3·3NH2(CH3)2NH(CH3)3·3H2O

310 194 309 314 311 192 309 319 195

-doheptanuclear/ cylindrical drumshaped -do-

195 312

[Zn8(Cl)6{2,3,5,6-(Me)4C6HCH2PO3}6(Et3N)2]·(Et3NH)2]·2nhexane·3H2O [Zn9(L)6(H2N(CH2)2NH(CH2)2NH(CH2)2NH2)2]·18H2O

octanuclear

314

nonanuclear

313

[Zn7L6][Zn(phen)2(H2O)2]2·19H2O

-do-

320

[Zn7L6{Zn(bipy)(H2O)3}2]·13.5H2O

-do-

320

[Zn6L6(Zn){Zn(H2O)4}2]·14H2O [Zn2(THF)2(EtZn)6Zn4(μ4-O)(t-BuPO3)8] Na6[ZnIIO8PdII12(PhPO3)8]·36H2O

-dododecanuclear tridecanuclear

320 308 274

(HN(C2H5)3)4[Zn7(L)6]·2H2O

This compound contains five ZnII ions arranged in a plane and two axial ZnII atoms. The two remaining ZnII atoms are connected to the central pentanuclear motif through carboxylate coordination. Notice that the phosphonates play a crucial role in the construction of the heptanuclear motif (Figure 169). The largest-sized ZnII phosphonate ensemble, [Zn 2(THF)2(EtZn)6Zn4(μ4-O)(t-BuPO3)8], has been synthesized in the reaction of t-BuPO3H2 and ZnEt2.308 In this structure, the 12 ZnII ions are held together by identical bridging modes of eight [t-BuPO3]2− ligands. The center of this dodecanuclear core contains a Zn4(μ4-O) motif. Interestingly, six of the zinc

313

atoms contain one ethyl group, while the remaining six ZnII ions do not possess alkyl substituents (Figure 170). A heterometallic tridecanuclear ZnII/PdII phosphonate complex, Na6[ZnO8Pd12(PhPO3)8]·36H2O, was obtained in the reaction of [Pd3(CH3CO2)6], ZnCl2, PhPO3H2, and NaOH.274 The symmetrical phosphonate cage contains a central ZnII ion that is encapsulated by 12 PdII ions. While the PdII centers are connected to each other by [PhPO3]2− ligands, ZnII is connected to the PdII centers through μ4-O ligands (Figure 171). All of the reported molecular ZnII phosphonates are listed in Table 23. CE


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Scheme 65. Synthesis of a Hexanuclear ZnII Phosphonate, [Zn6Cl4(3,5-Me2PzH)8(PhPO3)4]192

Figure 167. A heptanuclear ZnII phosphonate, (HN(C2H5)3)4[ Z n 7 ( L ) 6 ] · 2 H 2 O [ H 3 L = 1- C 1 0 H 7 − C H 2 N ( C H 2 C O 2 H ) (CH2PO3H2)].313 Adapted from ref 313. Copyright 2013 The Royal Society of Chemistry.

Figure 165. Molecular structure of a hexanuclear ZnII phosphonate, [{(ZnEt)3(Zn(THF))3}{t-BuPO3}4{3-OEt}].309 Adapted from ref 309. Copyright 2004 The Royal Society of Chemistry.

Figure 168. An ellipsoid-shaped octanuclear core of the Zn II phosphonate, [Zn 8 (Cl) 6 {2,3,5,6-(Me) 4 C 6 HCH 2 PO 3 } 6 (Et 3 N) 2 (Et3NH)2]·2n-hexane·3H2O.314 Adapted from ref 314. Copyright 2014 The Royal Society of Chemistry.

Interestingly, when the same reaction was performed in the presence of 2,2 ′ -bipyridine, a dinuclear compound [Cd 2 (ArPO 3 H) 4 (bipy) 2 ]·(CH 3 OH)·(H 2 O) was obtained (Scheme 66).323 The molecular structure of the dinuclear compound consists of a puckered eight-membered Cd2P2O4 ring resulting from the bridging of two cadmium centers through two [ArPO2(OH)]− ligands. The remaining two [ArPO2(OH)]− units function as terminal ligands coordinated to the CdII centers. The presence of the chelating bipyridine completes the coordination environment around each cadmium centers. All dinuclear CdII phosphonates are shown in Figure 173a and b.322−325 The tetranuclear compounds [Cd4(ArPO3)2(ArPO3H)4(CH3OH)4]·3CH3OH, [Cd4(ArPO3)2(ArPO3H)4(DMF)4]· 3DMF, and [Cd 4 (ArPO 3 ) 2 (ArPO 3 H) 4 (DMF) 2 (3,5Me2PzH)2]·2DMF·2H2O have been prepared without the involvement of ancillary nitrogen ligands (Scheme 67).323

Figure 166. A cylindrical drum-shaped heptanuclear core of the ZnII phosphonate, [Zn7{(2-C5H4N)CH(OH)PO3}6(H2O)6]SO4·4H2O.312 Adapted from ref 312. Copyright 2005 American Chemical Society.

15.2. Cadmium

Although molecular CdII phosphonates are less in comparison to those containing CuII or ZnII, the nuclearity of these complexes varies from 1 to 20.322 The reaction of Cd(OAc)2·2H2O with ArPO3H2 [ArPO3H2 = 2,4,6-i-Pr3C6H2PO3H2] in the presence of the ancillary ligand 3,5-Me2PzH afforded a mononuclear CdII molecular phosphonate, [Cd(ArPO3H)2(3,5-Me2PzH)4].323 In this complex, a single CdII ion is bound with two monodentate [ArPO3H]− and four 3,5-Me2PzH ligands (Figure 172). CF


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Figure 169. Nonanuclear core of a ZnII phosphonate, [Zn9(L)6(H2N(CH2)2NH(CH2)2NH(CH2)2NH2)2]·18H2O [H3L = 1-C10H7− CH2N(CH2CO2H)(CH2PO3H2)].313 Adapted from ref 313. Copyright 2013 The Royal Society of Chemistry.

Figure 170. A dodecanuclear ZnII phosphonate, [Zn2(THF)2(EtZn)6Zn4(μ4-O)(t-BuPO3)8].308 Adapted from ref 308. Copyright 1999 Wiley-VCH Verlag GmbH & Co. KGaA.

reaction. The reaction of Me2Cd with t-BuPO3H2 afforded this cage, which contains 20 cadmium atoms held together by 12[t-BuPO3]2−, 4[μ4-O]2−, and 2[μ3-OH]− ligands (Figure 175). All of the molecular cadmium phosphonates are summarized in Table 24.

These compounds, which are structurally similar, contain a planar arrangement of the cadmium atoms. The entire periphery of this array is stitched by four [ArPO2(OH)]− ligands, which are involved in bridging a pair of adjacent cadmium centers. The resultant array is further held together by two capping [ArPO3]2− ligands. All of the tetranuclear CdII phosphonates are listed in Table 24. The reaction of Cd(OAc)2·2H2O with m-phosphonophenylsulfonic acid (LH3) and phen or 4,4′-bipyridine under hydrothermal conditions afforded a hexanuclear CdII phosphonate cage, [Cd6(L)4(phen)8]·14H2O.324 The hexanuclear cage is assembled by the coordination action of the four L3− and eight chelating 1,10-phenanthroline ligands (Figure 174). Roesky et al. reported a Cd 20 phosphonate cage, [(MeCd)10{(THF)Cd}4Cd6(μ4-O)2(μ3-OH)2(t-BuPO3)12].322 The latter has been synthesized utilizing the alkane elimination

15.3. Mercury

Mononuclear HgII phosphonates are known.326 Thus, an in situ hydrolysis of [Hg{P(CF3)2}2(PMe3)2] afforded a mononuclear HgII phosphonate complex, [Hg{OP(O)CF3(OH)}2(PMe3)3] (Figure 176).326 On the other hand, the multicomponent reaction of [Hg{P(CF3)2}2(PMe3)2], CF3PO3H2, and PMe3 also afforded the same compound [Hg{OP(O)CF3(OH)}2(PMe3)3].326 In this compound, HgII is five-coordinate and adopts a distorted trigonal bipyramidal geometry. The oxygen atoms of the two monodentate phosphonate ligands occupy the axial positions. CG


Chemical Reviews

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Scheme 66. Synthesis of a Dinuclear CdII Phosphonate, [Cd2(ArPO3H)4(bipy)2]·(CH3OH)·(H2O)323

Figure 171. Tridecanuclear heterometallic core of Na6[ZnO8Pd12(PhPO3)8]·36H2O.274 Adapted from ref 274. Copyright 2012 American Chemical Society.

Figure 172. A mononuclear CdII phosphonate, [Cd(ArPO3H)2(3,5Me2PzH)4].323 Adapted from ref 323. Copyright 2008 The Royal Society of Chemistry.

16. LANTHANIDE PHOSPHONATES Majority of the reported 4f phosphonate complexes possess extended structures.327−333 The number of molecular analogues is relatively few. Among these, the nuclearity of the homometallic derivatives varies from 1 to 10,334 while in heterometallic systems the highest nuclearity achieved is 15.335 A mononuclear Eu III phosphonate, [C(NH 2 ) 3 ] 7 [Eu(EDTMP)(CO3)]·10H2O, was prepared in the reaction of EuCl3, H8EDTMP [H8EDTMP = ethylenediaminetetra(methylenephosphonic acid)], and Na2CO3.336 The molecular structure of this compound reveals a EuIII center surrounded by a monodentate phosphonate and chelating ethylenediamine and CO32− ligands (Figure 177a). Another example of a mononuclear compound is exemplified by the ErIII phosphonate complex, [H{Er(Hdo3ap)}·5H2O], which was synthesized in the reaction of 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic10-methylphosphonic acid (H5do3ap), ErCl3·6H2O, and LiOH.337 In this compound, the macrocyclic tetraaza ligand encapsulates the ErIII center, while the phosphonate and carboxylate ligands bind in a monodentate fashion. The eight

Figure 173. Dinuclear CdII phosphonates: (a) [NH3CH(CH3)CH 2 NH 3 ] 2 Cd 2 (edbbp) 2 ·H 2 O [eddbp = O 3 PCH(Ph)NH(CH2)2NHCH(Ph)PO3].318 Adapted from ref 318. Copyright 2004 Elsevier Masson SAS. (b) Cd 2{[(C 7H5 N2 )CH2] 2 NCH2 PO3 }2 · 2H2O.186 Adapted from ref 186. Copyright 2007 American Chemical Society.

coordinated ErIII center possesses a twisted-square-antiprismatic geometry (Figure 177b). The first dinuclear CeIII phosphonate, [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4], was synthesized by us, recently, from a reaction involving Ce(NO3)3·6H2O, Ph3CPO3H2, and NaOH under solvothermal conditions.44 The molecular structure of this compound reveals that two cerium atoms are CH


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Scheme 67. Synthesis of Various Tetranuclear CdII Phosphonates323

Figure 174. Molecular structure of a hexanuclear CdII phosphonate cage, [Cd6(L)4(phen)8]·14H2O (LH3 = m-phosphonophenylsulfonic acid).324 Adapted from ref 324. Copyright 2007 American Chemical Society.

complex, two EuIII centers are bridged by phosphonate ligands forming a puckered eight-membered ring. Each of the EuIII centers is further coordinated by two imine nitrogen atoms and one nitrogen atom from a pyridine group. The remaining two coordination sites of the EuIII ion are occupied by the bidentate carbonate ligand (Figure 179). A heterometallic dinuclear DyIII/Li phosphonate, {Li[Dy(Hdo3ap)]·5H2O]}, has been synthesized in the reaction of DyCl3·6H2O, H4dota (H5do3ap = 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid), and LiOH.337 In this complex, the DyIII ion possesses a twisted-squareantiprismatic geometry due to the coordination action of the tetraza macrocyclic ring and monodentate phosphonate and

−

bridged by a pair of isobidentate [Ph3CPO2(OEt)] ligands resulting in the formation of a puckered Ce2O4P2 eightmembered ring. The two cerium atoms are further bridged by two nitrate ligands, which generate another eight-membered (Ce2O4N2) ring. Each cerium atom is further coordinated to a monodentate [Ph 3CPO2(OEt)]− ligand and two water molecules (Figure 178). The dinuclear CeIII compound acts as a catalyst for the three-component Biginelli reaction. The reaction of Eu2O3, H4L [H4L = [ethane-1,2-diylbis{imino(pyridin-2-ylmethanediyl)}]bis(phosphonic acid)] and [C(NH2)3]2CO3 afforded a dinuclear EuIII phosphonate complex, [C(NH 2 )] 6 [Eu 2 (L) 2 (CO 3 ) 2 ]·8H 2 O. 338 In this Table 24. Molecular Cadmium Phosphonates


ref

[Cd(ArPO3H)2(3,5-Me2PzH)4] [Cd(dtbhpH)2(bipy)2](dtbhpH2)

mononuclear -do-

323 321

[Cd2(ArPO3H)4(bipy)2]·(CH3OH) ·(H2O) (Ar = i-Pr3C6H2) Cd2{[(C7H5N2)CH2]2NCH2PO3}2·2H2O

dinuclear

323

-do-

186

[NH3CH(CH3)CH2NH3]2Cd2(edbbp)2·H2O [Cd4(L)4(phen)4]·4H2O [Cd4(L)4(phen)4]·6H2O [Cd4(ArPO3)2(ArPO3H)4(CH3OH)4]·3(CH3OH) (Ar = i-Pr3C6H2) [Cd4(ArPO3)2(ArPO3H)4(DMF)4]·3(DMF) (Ar = i-Pr3C6H2) [Cd4(ArPO3)2(ArPO3H)4(DMF)2(3,5-Me2PzH)2]· 2(DMF)·2(H2O) (Ar = i-Pr3C6H2) [Cd4(FMPA)4(phen)4]·7CH3OH [Cd4(L)2(phen)6(Cl)2(H2O)2]·14H2O [Cd6(L)4(phen)8]·14H2O [(MeCd)10{(THF)Cd}4Cd6(μ4-O)2(μ3-OH)2(tBuPO3)12]

-dotetranuclear tetranuclear -do-

318 325 325 323

-do-

323

-do-

323

-do-dohexanuclear icosanuclear

311 324 324 322

reactants 2,4,6-i-Pr3C6H2PO3H2 Cd(OAc)2·2H2O, 3,5-Me2PzH Cd(ClO4)2·H2O, bipy, 3,5-di-tert-butyl-2-hydroxybenzylphosphonic acid (dtbhpH2) 2,4,6-i-Pr3C6H2PO3H2, Cd(OAc)2·2H2O, bipy CdSO4·2.7H2O, bis(benzimidazol-2-ylmethyl)imino (methylene phosphonic acid) [{(C7H5N2)CH2}2NCH2PO3H2] [O3PCH(Ph)NH(CH2)2NHCH(Ph)PO3](eddbp), Cd(NO3)2·4H2O Cd(ClO4)2, (PhCH2)2NCH2PO3H2 CdSO4, (PhCH2)2NCH2PO3H2 2,4,6-i-Pr3C6H2PO3H2, Cd(OAc)2·2H2O 2,4,6-i-Pr3C6H2PO3H2, Cd(OAc)2·2H2O, DMF 2,4,6-i-Pr3C6H2PO3H2, Cd(OAc)2·2H2O, 3,5-Me2PzH, DMF Cd(OAc)2·2H2O, FcCH2PO3H2 (FMPAH2), phen, NEt3 m-phosphonophenylsulfonic acid (LH3), phen, Cd(OAc)2·2H2O m-phosphonophenylsulfonic acid (LH3), phen, Cd(OAc)2·2H2O Me2Cd, t-BuPO3H2, THF

compounds

CI


Chemical Reviews

Review

Figure 178. A dinuclear CeIII phosphonate, [Ce2{Ph3 CPO2(OEt)}4(NO3)2(H2O)4].44 Adapted from ref 44. Copyright 2008 The Royal Society of Chemistry.

Figure 175. An icosanuclear core of the CdII phosphonate, [(MeCd)10{(THF)Cd}4Cd6(μ4-O)2(μ3-OH)2(t-BuPO3)12].322 Adapted from ref 322. Copyright 2003 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 176. A mononuclear HgII phosphonate, [Hg{OP(O)CF3(OH)}2(PMe3)3].326 Adapted from ref 326. Copyright 2002 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 179. A dinuclear EuIII phosphonate, [C(NH2)]6[Eu2(L)2(CO 3 ) 2 ]·8H 2 O [H 4 L = [ethane-1,2-diyl-bis{imino(pyridin-2ylmethanediyl)}]bis(phosphonic acid)].338 Adapted from ref 338. Copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

carboxylate ligands. The carboxylate ligand also serves to connect the LiI and DyIII centers (Figure 180).

Recently, Winpenny et al. have reported a trigonal pyramidal shaped tetranuclear LnIII phosphonate cage, [pyH]4[Ln4(μ3-

Figure 177. Mononuclear phosphonates: (a) [C(NH2)3]7[Eu(EDTMP)(CO3)]·10H2O [H8EDTMP = ethylenediaminetetra(methylenephosphonic acid)].336 Adapted from ref 336. Copyright 2006 The Royal Society of Chemistry. (b) [H{Er(Hdo3ap)}·5H2O] (H5do3ap = 1,4,7,10tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid).337 Adapted from ref 337. Copyright 2005 American Chemical Society. CJ


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Figure 180. A heterometallic dinuclear DyIII/LiI phosphonate, [Li{Dy(Hdo3ap)}·5H2O}] (H5do3ap = 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid).337 Adapted from ref 337. Copyright 2005 American Chemical Society.

Figure 182. A heterometallic complex, [Dy4K2O(OBu-t)12]·C6H14, which behaves as a single-molecule magnet.340 Adapted from ref 340. Copyright 2013 Macmillan Publishers Ltd.

Figure 183. Molecular structure of [Dy 8 (O 3 PBu-t) 6 (μ 3 OH)2(H2O)2(HOBu-i)(O2CBu-t)12]·(NH3Pr-i)2.341 Adapted from ref 341. Copyright 2013 The Royal Society of Chemistry.

Figure 181. A pyramid-shaped tetranuclear DyIII phosphonate, [pyH]4[Dy4(μ3-OH)(O3PBu-t)3(HO3PBu-t)(O2CBu-t)2(NO3)6].339 Adapted from ref 339. Copyright 2014 The Royal Society of Chemistry.

There are no reports on penta-, hexa-, and heptanuclear molecular LnIII phosphonate complexes. An octanuclear LnIII phosphonate, [Ln 8 (O 3PBu-t) 6 (μ3 -OH)2 (H 2 O) 2 (HOBu-i)(O2CBu-t)12]·(NH3Pr-i)2 (Ln = Gd, Dy, Tb), was prepared in the reaction of Ln(NO3)3·6H2O, t-BuCO2H, t-BuPO3H2, i-PrNH2, and i-BuOH.341 The molecular structure of this compound possesses a horseshoe shaped core. The latter contains eight lanthanides that are connected to each other through the six bridging phosphonates and 12 pivalate ligands. Particularly important is the role of the two central phosphonate ligands that connect two tetranuclear subunits enabling the formation of the octanuclear compound (Figure 183). Nonanuclear LnIII phosphonates, [Ln9(OH)(Hpmp)12(ClO4)(H2O)26]·(ClO4)13·18H2O [Ln = Nd, Pr], were obtained in the reaction of Ln(ClO4)3, H2pmp [H2pmp = Npiperidinomethane-1-phosphonic acid], and NaOH (Figure 184).342 All of the molecular LnIII phosphonates described above were prepared using multicomponent reactions. In contrast, a decanuclear LnIII phosphonate cage has been synthesized

OH)(O3PBu-t)3(HO3PBu-t)(O2CBu-t)2(NO3)6] [Ln = GdIII, TbIII, DyIII, HoIII, ErIII].339 These compounds have been prepared in multicomponent reactions involving Ln(NO3)3· 6H2O, t-BuPO3H2, and t-BuCO2H in the presence of pyridine as a base in iso-butanol solvent. The molecular structure of this compound reveals that the four lanthanide ions are held together by four phosphonates, six nitrates, one μ3-OH, and two pivalate ligands. The core of this cage is pyramid-shaped; three LnIII ions are in a plane while the remaining LnIII lies above the plane. Three phosphonate ligands cap the triangular faces of the pyramid, while the fourth phosphonate ligand is located below the base of a triangular pyramid (Figure 181). Although unrelated to the phosphonate complexes, mention must be made of a heterometallic complex, [Dy4K2O(OBut)12]·C6H14 (Figure 182), whose magnetic studies reveal it to be a single-molecule magnet with a very large energy barrier for the reversal of magnetization Ueff = 842 K.340 CK


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Figure 184. A nonanuclear phosphonate, [Pr9(OH)(Hpmp)12(ClO4)(H2O)26]·(ClO4)13·18H2O [H2pmp = N-piperidinomethane-1-phosphonic acid].342 Adapted from ref 342. Copyright 2009 Elsevier Masson SAS.

Figure 186. A heterometallic pentadecanuclear Na6Eu9 phosphonate, [Na6Eu9L16](OH)·51H2O (H2L = 5′-methyl-2,2′-bipyridyl-6-phosphonic acid).335 Adapted from ref 335. Copyright 2006 American Chemical Society.

Figure 185. A decanuclear phosphonate, [Dy10(O2CBu-t)18(O3PBut)6(OH)(H2O)4], containing a central DyIII surrounded by nine other DyIII centers.334 Adapted from ref 334. Copyright 2014 The Royal Society of Chemistry.

(H2L), and NaOH.335 In this complex, nine EuIII and six NaI ions are held together by 16 L2− bridging ligands. The molecular structure of this compound reveals two symmetryrelated Na3Eu4 subunits that are connected to each other through a bridging phosphonate ligand. To fulfill the coordination number of the EuIII entering, the bipy ligand acts as a chelating ligand (Figure 186). All of the known molecular LnIII phosphonates are listed in Table 25.

utilizing the cluster expansion strategy. The reaction of [Ln2(O2CBu-t)6(HO2CBu-t)6] (Ln = Dy, Gd), [Co3(μ3-O)(O2CBu-t)6(py)3]·(O2CBu-t), and t-BuPO3H2 in the presence of pyridine afforded [Ln10(O 2CBu-t) 18(O 3PBu-t) 6(OH)(H2O)4] (Ln = Dy, Gd), which cocrystallized along with the cobalt complex, [Co3(μ3-O)(O2CBu-t)6(py)3].334 The decanuclear compound contains a central LnIII ion that is connected to nine other LnIII ions through bridging [t-BuPO3]2− ligands. The periphery of the complex is occupied by carboxylate ligands (Figure 185). A heterometallic pentadecanuclaer Eu/Na phosphonate, [Na6Eu9L16](OH)·51H2O, was obtained in the reaction of Eu(ClO4)3·6H2O, 5′-methyl-2,2′-bipyridyl-6-phosphonic acid

17. MOLECULAR ACTINIDE PHOSPHONATES The reported actinide (U and Th) metal phosphonates possess extended structures.343−347 A heterometallic UIII/NiII molecular phosphonate, [H3O]4[Ni(H2O)3]4[Ni{(UO2)(PO3C6H4CO2)}3(PO4H)]4·2.72H2O, has been described in the NiII section.260 CL


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Table 25. Molecular Lanthanide Phosphonates reactants ethylenediaminetetra(methylenephosphonic acid) (H8EDTMP), NaOH, Eu2O3, Na2CO3, EuCl3 ErCl3·6H2O, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10methylphosphonic acid (H5do3ap) LuCl3·6H2O, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10methylphosphonic acid (H5do3ap) LiOH, TbCl3·5H2O, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic10-methylphosphonic acid (H5do3ap) Ph3CPO3H2, Ce(NO3)3·6H2O, NaOH Eu2O3, [ethane-1,2-diylbis{imino(pyridin-2-ylmethanediyl)}] bis(phosphonic acid) (H4L), [C(NH2)3]2CO3 LiOH, DyCl3·6H2O 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic10-methylphosphonic acid (H5do3ap) LiOH, LuCl3·6H2O 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic10-methylphosphonic acid (H5do3ap) LiOH, YCl3·6H2O (Ln = Dy, Lu, Y), 1,4,7,10-tetraazacyclododecane1,4,7-triacetic-10-methylphosphonic acid (H5do3ap) t-BuCO2H, Ln(NO3)3.6H2O, HOBu-i, pyridine, t-BuPO3H2 t-BuCO2H, Ln(NO3)3·6H2O, t-BuPO3H2, i-PrNH2, i-BuOH Nd(ClO4)3, NaOH, N-piperidinomethane−1-phosphonic acid (H2pmp) Pr(ClO4)3, NaOH, N-piperidinomethane−1-phosphonic acid (H2pmp) [Ln2(O2CBu-t)6(HO2CBu-t)6] (Ln = Dy, Gd) [Co3(μ3-O) (O2CBu-t)6(py)3](O2CBu-t), t-BuPO3H2, pyridine 5′-methyl-2,2′-bipyridyl-6-phosphonic acid (H2L), Eu(ClO4)3·6H2O, NaOH

compounds


ref

[C(NH2)3]7[Eu(EDTMP)(CO3)]·10H2O

mononuclear

336

[H{Er(Hdo3ap)}·5H2O]

337

[H{Lu(Hdo3ap)}·6H2O]

mononuclear/twisted-squareantiprismatic -do-

[Li{Tb(Hdo3ap)(H2O)}·0.5HCl·5H2O]

-do-

337

[Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4] [C(NH2)]6[Eu2(L)2(CO3)2]·8H2O

dinuclear -do-

44 338

[Li{Dy(Hdo3ap)}·5H2O]

337

[Li{Lu(Hdo3ap)}·5H2O]

heterometallic dinuclear/ twisted-square-antiprismatic -do-

[Li{Y(Hdo3ap)}·5H2O]

-do-

337

[pyH]4[Ln4(μ3-OH)(O3PBu-t)3(HO3PBu-t) (O2CBu-t)2(NO3)6] [Ln = Gd, Tb, Dy, Ho, Er] [Ln8(O3PBu-t)6(μ3-OH)2(H2O)2(HOBu-i)(O2CBut)12](NH3Pr-i)2 (Ln = Gd, Dy, Tb) [Nd9(OH)(Hpmp)12(ClO4)(H2O)26](ClO4)13· 18H2O [Pr9(OH)(Hpmp)12(ClO4)(H2O)26](ClO4)13· 18H2O [Co3(μ3-O)(O2CBu-t)6(py)3][Ln10(O2CBu-t)18 (O3PBu-t)6 (OH)(H2O)4] (Ln = Dy, Gd) [Na6Eu9L16](OH)·51H2O

tetranuclear

339

octanuclear/horseshoe-shape

341

nonanuclear/nanoscale lotusleaf-shaped -do-

342

decanuclear

334

pentadecanuclear

335

337

337

342

Figure 187. 1.100 coordination binding mode of the phosphonate ligands.273 Adapted from ref 273. Copyright 2007 The Royal Society of Chemistry.

Figure 188. 1.110 coordination binding mode. P−O bond distances: P(1)−O(1), 1.489(2) Å; P(1)−O(2), 1.575(2) Å; P(1)−O(3), 1.579(2) Å.277 Adapted from ref 277. Copyright 2011 Elsevier Masson SAS. CM


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Figure 189. 2.200 coordination binding mode of the phosphonate ligand. P−O distances: P(1)−O(1), 1.545(2) Å; P(1)−O(2), 1.511(2) Å; P(1)− O(3), 1.504(3) Å.186 Adapted from ref 186. Copyright 2007 American Chemical Society.

Figure 190. 2.110 coordination modes of the phosphonate ligands resulting in the formation of (a) an eight-membered Mn2P2O4 ring in [Mn2(tBuPO3H)4(phen)2]·2DMF,36 (b) two six-membered Nb2O3P rings in [n-Bu4N]2[Nb2(μ-O)(OMe)6(O3PPh)2],129 and (c) a capping coordination to a V2O2 ring in [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]·2CH3OH·0.5CH2Cl2.143

19. COORDINATION FEATURES OF THE PHOSPHONATE LIGAND After the detailed account on various metal phosphonates, this section attempts to summarize the general coordination features/modes of the phosphonate ligand. As we have noted, in general, both anionic [RP(OH)(O2)]− and dianionic [RPO3]2− forms (in some instances the neutral ligand), [RP(O)(OH)2], are involved in binding to the metal ions. The possible binding modes of [RPO3]− and [RP(OH)(O2)]− ligands have been summarized in Figures 3 and 4. Although the maximum binding capacity of the [RPO3]2− ligand is up to 9 metal ions, there is not a single instance where this potential

has been reached. In this section, we will try to exemplify the various coordination modes of the phosphonate ligand ranging from 1.100 to 7.322. In the 1.100 coordination binding mode, the phosphonate ligands only bind in a η1-coordination fashion. In general, such a mode is found where the metal ion favors lower coordination numbers or where the metal ions already possess significant coordination ligands around them. A mononuclear PdII phosphonate complex is shown in Figure 187, where the phosphonate ligand binds in a 1.100 coordination mode. The P−O bond distances observed in this mode are P(3)−O(5), 1.495(7) Å; P(3)−O(7), 1.524(9) Å; and P(3)−O(6), CN


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Figure 191. 3.111 coordination binding mode of the phosphonate ligands generating (a) trinuclear propellane-type architecture, [Mn3(tBuPO3)2(dpzpy)3]·(ClO4)2·H2O,36 (b) tetranuclear open-book structure, [Mn4(t-BuPO3)2(t-BuPO3H)2(phen)6(H2O)2]·(ClO4)2,36 (c) tetranuclear linear [Mn4(C5H9PO3)2(phen)8(H2O)2]·(ClO4)4,36 and (d) tetranuclear distorted cubic/D4R ring, [Fe4(t-BuPO3)4(HphpzH)4]·5CH3CN· 5CH2Cl2, having a D4R type core.218 Parts a−c adapted from ref 36. Copyright 2012 American Chemical Society. Part d adapted from ref 218. Copyright 2014 American Chemical Society.

other two.277 This is reminiscent of the anisobidentate coordination behavior of the carboxylate ligand. In the 2.200 coordination mode, a single oxygen atom of the phosphonate ligand is involved in coordination. Thus, in the complex Mn2[{(C7 H5N2 )CH2}2 NCH2PO 3]2(H2O) 2·2H2O (Figure 189), while two oxygen atoms of the phosphonate ligand are free, the third is involved in a μ2-bridging mode,

1.536(5)Å. As can be seen, despite the fact that only O5 is involved in binding to Pd, the other P−O distances, although slightly longer, are not very different.273 In the 1.110 coordination binding mode the phosphonate ligands bind in a chelating manner as exemplified in a PtII complex (Figure 188). Note that in this case one of the P−O distances, P(1)−O(1), 1.489(2) Å, is much shorter than the CO


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Figure 192. 3.111 coordination modes observed in the following: (a) [VIII5(μ3-OH)(O3PBu-t)6Cl2(Py)6].142 Adapted from ref 142. Copyright 2007 Wiley-VCH Verlag GmbH & Co. KGaA. (b) [(VVO)5(VIVO)(t-BuPO3)8Cl].153 Adapted from ref 153. Copyright 1994 Wiley-VCH Verlag GmbH & Co. KGaA. (c) [HNEt3]2[(V8O16){V4O4(H2O)12}(Ph2CHPO3)8Cl2]·(H2O)7·(CH3CN)4.157 Adapted from ref 157. Copyright 2008 American Chemical Society. (d) [{Fe36(2-PyPO3)44(H2O)48}]·(ClO4)2.1(NO3)11.9(OH)6·47·9H2O·10EtOH.217 Adapted from ref 217. Copyright 2013 American Chemical Society. This mode leads to the formation of the highest nuclearity of the Fe36 phosphonate cage.

six-membered rings.129 The P−O bond distances found in this instance are P(1)−O(8), 1.543(2) Å; P(1)−O(9), 1.544(2) Å; and P(1)−O(10), 1.481(2) Å. In the VV complex, [(VO)2(bipy)2(μ2-O)2(t-BuPO3)2]· 2CH3OH·0.5CH2Cl2, only one phosphonate ligand is involved in binding along with two μ-oxo ligands.143 This results in the formation of a V2O2 ring that is capped by the phosphonate ligand. The corresponding P−O bond distances are P(1)− O(5), 1.553(5) Å; P(1)−O(6), 1.498(5) Å; and P(1)−O(7), 1.558(5) Å (Figure 190c). The 3.111 binding mode of the phosphonate ligand is observed in many instances. In this situation, every oxygen atom of the phosphonate ligand is found to be binding to a metal center. This mode of binding is found in complexes whose nuclearity varies from 3 to 36. Some examples are illustrated in Figures 191 and 192. In the trinuclear MnII complex, [Mn3(t-BuPO3)2(dpzpy)3]·(ClO4)2·H2O,36 the two phosphonate ligands help to stitch the three metal centers together to achieve a propellane-type architecture (Figure 191). Unlike in the cases discussed above, in this instance, the three P−O bond distances are very similar: P(1)−O(4), 1.529(3) Å; P(1)−O(6), 1.534(3) Å; and P(1)−O(5), 1.540(3) Å.36

resulting in a Mn2O2 four-membered ring. The P−O distance involved in the bridging mode {1.545(2) Å} is longer than the other P−O bond distances.186 In the 2.110 coordination mode, the phosphonate ligands function to bridge two metal centers generating a puckered eight-membered (M2P2O4) ring. Some of the representative examples where the 2.110 mode is exhibited are shown in Figure 190. While the Mn I I complex, [Mn 2 (t-BuPO3H)4(phen)2]·2DMF, conforms to the description given above, the situation in the niobium and the vanadium complexes is different. In the MnII complex, the observed P− O bond distances are P(1)−O(1), 1.499(2) Å; P(1)−O(3), 1.510(2) Å; and P(1)−O(2), 1.579(2) Å.36 The latter corresponds to the P−OH unit. Note that in this complex two [t-BuP(O)2OH]− ligands function as terminal ligands in a 1.100 mode. In this case, the P−O distances are P(2)−O(4), 1.515(2) Å; P(2)−O(5), 1.573(2) Å; and P(2)−O(6), 1.495(2) Å (Figure 190a).36 In the Nb V complex, [n-Bu 4 N] 2 [Nb 2 (μ-O)(OMe) 6 (O3PPh)2],129 shown in Figure 190b, in addition to the two phosphonate ligands that bind in a 2.110 mode, a central μ-oxo ligand binds the two NbV centers generating two Nb2O3P CP


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Figure 193. 4.211 coordination mode of phosphonate ligands leads to the formation of the following: (a) a pentanuclear FeIII complex, [HNEt3]2[Fe5(μ3-O)(μ-OH)2(Cl3CPO3)3(HphpzH)5(μ-phpzH]·3CH3CN·2H2O.218 Adapted from ref 218. Copyright 2014 American Chemical Society. (b) A hexanuclear MnIII complex, [Mn6III(O)2(PhCO2)8(PhPO3)2(PhPO3H)2(py)2].197 Adapted from ref 197. Copyright 2006 The Royal Society of Chemistry.

In the 5.221 coordination binding mode of the phosphonate ligands, two oxygen atoms are involved in bridging coordination, while the remaining oxygen atom binds to the metal center in a η1-coordination manner. A nonanuclear icosahedral Fe III phosphonate complex, [Fe 9 III (μ 3 -O) 4 (O 3 PC 5 H 9 ) 3 (O2CCMe3)13]3, exemplifies this mode (Figure 194). The P− O bond distances are P(3)−O(9), 1.515(4) Å; P(3)−O(10), 1.538(4) Å; and P(3)−O(8), 1.548(4) Å. The η1-coordinated P−O bond is shorter than the bridging P−O bond distances. This coordination binding mode of the phosphonate ligands is also involved in other high nuclearity metal clusters such as [Co14(OH) 4(chp)2(O3PCh2Ph)2(H2O)2]237 and [MnIII16MnIV2(μ3-O)8(PhPO3)14(O2CCMe3)12(py)6(H2O)2].198 In the former case, two Co7 subunits are held together by two bridging phosphonate ligands (Figure 194). In case of the octadecametallic mixed-valent MnIII16MnIV2 phosphonate cage, alternate Mn3O units are connected to each other through the bridging phosphonate ligands (Figure 194). In the 6.222 coordination mode of the phosphonate ligands, three oxygen atoms of the P−O ligands are involved in a

Coordination modes, 4.211 and above, allow the phosphonate ligands to build larger ensembles as a result of the increased binding to metal sites. Representative examples are summarized in Figure 193. In an example involving the 4.211 coordination mode of the phosphonate ligand, in a pentanuclear FeIII phosphonate cage, [HNEt 3 ] 2 [Fe 5 (μ 3 -O)(μ-OH) 2 (Cl 3 CPO 3 ) 3 (HphpzH) 5 (μphpzH]·3CH3CN·2H2O (Figure 193a),218 one oxygen atom of the phosphonate ligands is involved in bridging two Fe-centers and the remaining two oxygen atoms are η1-coordinated to Fecenter. The corresponding P−O bond parameters are P(3)− O(4), 1.498(5) Å; P(3)−O(5), 1.516(5) Å; and P(3)−O(6), 1.534(5)Å. These bond distances suggest that the bridging P− O bond is longer than the other two η1-coordinate P−O bond distances.218 In a hexanuclear MnIII phosphonate complex, [Mn6III(O)2(PhCO2)8(PhPO3)2(PhPO3H)2(py)2], two trinuclear Mn3O subunits are connected to each other through bridging 4.211 coordination of the phosphonate ligands (Figure 193b).197 In this case, phosphonate ligands play a crucial role in the final assembly of the high-nuclearity complex. CQ


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Figure 194. 5.221 coordination mode of the following: (a) nonanuclear icosahedral FeIII complex, [Fe9III(μ3-O)4(O3PC5H9)3(O2CCMe3)13].3 Adapted from ref 3. Copyright 2014 Wiley-VCH Verlag GmbH & Co. KGaA. (b) Tetradecanuclear cobalt(II) complex, [Co14(OH)4(chp)2(O3PCh2Ph)2(H2O)2].237 Adapted from ref 237. Copyright 2008 American Chemical Society. (c) Octadecanuclear mixedvalent manganese phosphonate complex, [MnIII16MnIV2(μ3-O)8(PhPO3)14(O2CCMe3)12(py)6(H2O)2].198 Adapted from ref 198. Copyright 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

Figure 195. 6.222 coordination binding mode of the decanuclear cobalt(II) phosphonate complex, [Co10(chp)12(O3PPh)2(O2CPh)4(H2O)4].242 Adapted from ref 242. Copyright 2012 The Royal Society of Chemistry.

bridging coordination fashion. Thus, in the decanuclear CoII phosphonate complex, [Co 10 (chp) 12 (O 3 PPh) 2 (O 2 CPh) 4 (H2O)4],242 two Co5 motifs are connected to each other through the bridging phosphonate ligands, which bind in a

6.222 coordination binding mode (Figure 195). The P−O bond distances found in this complex are very similar: P(1)− O(7), 1.527(1) Å; P(1)−O(8), 1.535(1) Å; and P(1)−O(14), 1.542(1) Å. CR


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Figure 196. 7.322 coordination modes observed in the Na8Co6 phosphonate cage, [Co6Na8(chp)12(O3PPh)4(MeCN)4].239,241 Adapted from ref 239. Copyright 2004 The Royal Society of Chemistry.

Figure 198. (a) A dinuclear MnII carboxylate complex, [L2MnII2(μ-O2CCH3)3(BPh4) (L = N,N″,N″-trimethyl-l,4,7-triazacyclononane) (J = −3.5 cm−1).348 Adapted from ref 348. Copyright 1988 American Chemical Society. (b) A dinuclear MnII phosphate complex, [{(phen)2Mn}2(μ-P2O7)]·13H2O (J = −0.88 cm−1).349 Adapted from ref 349. Copyright 2007 American Chemical Society. Figure 197. Dinuclear MnII phosphonate complexes: (a) [Mn2(tBuPO3H)4(phen)2] (J = −0.015 cm−1).36 adapted from ref 36. Copyright 2012 American Chemical Society. (b) [Mn2(t-BuPO3H)4(bipy)2] (J = −0.70 cm−1).185 Adapted from ref 185. Copyright 2007 Elsevier Masson SAS.

[Co6Na8(chp)12(O3PPh)4(MeCN)4]239,241 (Figure 196). The P−O bond distances found here are P(2)−O(8), 1.523(2) Å; P(2)−O(9), 1.527(2) Å; and P(2)−O(10), 1.541(2) Å. It can be seen that the P−O bond distance involving the μ3-oxygen is slightly longer than that involving the μ2-oxygen.

The maximum binding capability of the phosphonate ligand is 9. However, this mode has not been found, thus f ar. The highest coordination exhibited by the phosphonate ligands is 7.322, which is found in the heterometallic tetradecanuclear cobalt(II) phosphonate cage,

19. APPLICATIONS OF MOLECULAR METAL PHOSPHONATES The main focus of this Review is on the synthetic and structural aspects of molecular metal phosphonates. Nevertheless, in this CS


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Figure 201. Coupling pathways and the corresponding coupling constants in the heptanuclear iron(III) complex, [Fe 7 (μ 3-O) 2 (t-BuPO3)4(t-BuCO2)8(py)8]·(NO3) (J1 = −27.4 cm−1, J2 = − 18.7 cm−1, and J3 = −0.8 cm−1).223

Table 26. Magnetic Data of Representative Complexes Containing Phosphonate Ligands along with Some Other Bridging Ligands compounds [Mn2(t-BuPO3H)4(phen)2]·2DMF [Mn2(t-BuPO3H)4(bipy)2] [L2MnII2(μ-O2CCH3)3](BPh4) (L = N,N″,N″trimethyl-l,4,7-triazacyclononane) [MnII2L2(H2O)4]·(ClO4)2·H2O (LH = (bis(2pyridylmethyl)amino)acetic acid) [{(phen)2Mn}2(μ-P2O7)]·13H2O [Mn3(C5H9PO3)2(phen)6]·(ClO4)2·7CH3OH [Mn3(Me3CCO2)6(Me3CCO2H)5]· 2(Me3CCO2H) [Cu2(μ2-C3H7PO3)2(bpya)2(H2O)2]·(H2O)2 [Cu3(C5H9PO3)2(bpy)3(MeOH)(H2O)]·(ClO4)2 [Cu3(C5H9PO3)2(μ-Cl)(bpya)3(H2O)]·(ClO4) [Cu2(O2CC6H3-2,6-OMe)4(H2O)4] [Cu2(O2CCH3)2(O2CC6H3-2,6-OMe)2(H2O)4] [Fe7(μ3-O)2(t-BuPO3)4(t-BuCO2)8(py)8]·(NO3)

Figure 199. A trinuclear Mn I I phosphonate complex, [Mn3(C5H9PO3)2(phen)6]·(ClO4)2·7CH3OH (J = −0.17 cm−1).36 Adapted from ref 36. Copyright 2012 American Chemical Society.

antiferromagnetic coupling values (J, cm−1)

ref

−0.015 −0.70 −3.5

36 185 348

−0.631

350

−0.88 349 −0.17 36 J1 = −0.588, J1 = −0.855 351 −1.547 −4.4 −3.8 −163 −125 J1 = −27.4, J2 = −18.7, J3 = −0.8

187 282 282 352 352 223

[L2MnII2(μ-O2CCH3)3(BPh4)] (L = N,N″,N″-trimethyl-l,4,7triazacyclononane) (J = −3.5 cm−1) (Figure 198a)348 and [{(phen)2Mn}2(μ-P2O7)]·13H2O (J = −0.88 cm−1) (Figure 198b).349 A situation similar to that found above is also encountered in trinuclear MnII derivatives. Thus, the complex [Mn3(C5H9PO3)2(phen)6]·(ClO4)2·7CH3OH shows J = −0.17 cm−1 (Figure 199),36 which is comparable to that found in a structurally analogous carboxylate complex, [Mn3(Me3CCO2)6(Me3CCO2H)5]·2(Me3CCO2H) [J1 = −0.588 cm−1, J2 = −0.855 cm−1] (Figure 200).356 A heptanuclear complex, [Fe7(μ3-O)2(t-BuPO3)4(t-BuCO2)8(py)8]·(NO3), contains two Fe3O motifs that are connected to a central FeIII through the 3.111 bridging coordination of the [t-BuPO3]2− ligands.223 Within the trinuclear motif, the irons are connected to each other not only through the μ3-O but also through carboxylate ligands. An analysis of the magnetic data revealed the presence of three exchange interactions: (a) through the μ3-O and the two carboxylate bridges (J1); (b) through μ3-O and two phosphonate bridges (J2); and (c) between the central FeIII and three FeIII centers in the {Fe3(μ3-O)} cores via O−P−O bridges (J3) (Figure 201). The corresponding J values are J1 = −27.4 cm−1, J2 = −18.7 cm−1, and J3 = −0.8 cm−1. Note that in this instance the weakest coupling is mediated through the phosphonate ligands. The magnetic data of some representative examples are summarized in Table 26. Many complexes containing the phosphonate ligand have also shown single-molecule magnet properties. However, in

Fig ure 20 0. A tr in uc le a r M n I I ca rbox yla te c omp lex, [Mn3(Me3CCO2)6(Me3CCO2H)5]·2(Me3CCO2H) [J1 = −0.588 cm−1, J2 = −0.855 cm−1].351 Adapted from ref 351. Copyright 2004 The Royal Society of Chemistry.

section, we will briefly allude to some of the important properties of these compounds choosing representative examples. 19.1. Magnetic Properties

In general, the phosphonate ligand has been shown to be a weak mediator of exchange coupling between paramagnetic metal ions. In most cases, an antiferromagnetic exchange coupling has been observed between metal ions that are bridged through the phosphonate ligand. A few examples are illustrated below. The dinuclear complexes, [Mn2(t-BuPO3H)4(phen)2] (J = −0.015 cm−1) and [Mn2(t-BuPO3H)4(bipy)2] (J = −0.70 cm−1), contain two manganese(II) ions that are connected to each other by the [t-BuPO2(OH)]− ligand (Figure 197a and b).36,185 Both of these complexes show very weak antiferromagnetic exchange. The J value observed in these cases is comparable to structurally similar dinuclear MnII complexes containing either carboxylate or phosphate bridging ligands, CT


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Table 27. Representative Metal Complexes Containing Phosphonate Ligands That Exhibit Single-Molecule Magnetism compounds [Et3NH]2[MnIII18MnII2(μ4-O)8(μ3-O)4(μ3OH)2(O3PCH2Ph)12(O2CCMe3)10(py)2] K4[MnIII16MnII4(μ4-O)4(μ3-O)6 (PhCH2PO3)14(PhCO2)12(PhCO2H)0.5(CH3CN)2] [Mn9Na(μ3-O)4(μ4-O)2 (O3PPh)2(O2CCMe3)12(H2O)2(H2O)0.67(Py)0.33] [Et3NH][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2] [HNEt3][Co8(chp)10(O3PPh)2(NO3)3(Hchp)2]

magnetic properties

energy barrier (Ueff/K), time constant (τ0/s)

ref

single molecule magnet (SMM) SMM

Ueff = 43, τ0 = 2.0 × 10−11

181

Ueff = 17, τ0 = 2.0 × 10−10

349

SMM

Ueff = 17.7

198

SMM SMM

Ueff = 80, τ0 = 1.8 × 6 × 10−12 (hysteresis loop at 4 K) Ueff = 84 K, τ0 = 1.8 × 10−12, Ueff = 80 K, τ0 = 2.1× 10−11

240 237

Table 28. List of 3d/4f and 4f Molecular Phosphonate Complexes That Are Potential Magnetic Coolants compounds

applied field (ΔH in KG)b

ΔSM(T) (J kg−1 K−1) [Sm = R ln(2S + 1), R = NAkB]a

ref

70 70

28 33.7

25 25

70 70 70 70 70

13 22.3 19.9 20.4 32.6

25 21 21 21 22

70

19.7

22

70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70 70

11.8 20.0 21.1 21.4 23.6 28.6 37.4 33.8 14.3 32 28.2 27.9 26.5 26.6 25.4 22.0 22.9 45.9 28.5

1 1 1 1 1 1 7 7 7 23 23 23 23 23 23 23 23 341 334

[MnII9GdIII9(O3PMe)(O2CBu-t)18(μ3-OH)1.5(O2CBu-t)1.5] [MnII4GdIII6(O3PCH2Ph)6(HO2CBu-t)13(O2CMe3)(HO2CBu-t)(OH) (MeCN)2 [MnII6DyIII6(μ3OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCN)5 [CoII4GdIII6(O3PCH2Ph)6(O2CBu-t)14(MeCN)2] [CoII8GdIII4(O3PBu-t)6(O2CBu-t)16] [CoII8GdIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16] [Co4Gd10(O2CBu-t)12 (O3PC6H10NH2)8(PO4)2(O2CMe)2(O3PC6H10NH3)2] [Co4Dy10(O2CBu-t)12 (O3PC6H10NH2)8(PO4)2(O2CMe)2(O3PC6H10NH3)2] [CoII8GdIII2(μ3-OH)2 (O3PCH2Ph)4(O2CBu-t)12(HO2CMe)2](MeCN)6 [CoII4GdIII2(O3PBu-t)2(O2CBu-t)10(MeCN)2]·(MeCN)2 [CoII8GdIII4(O3PBu-t)6(O2CBu-t)16] [CoII8GdIII8(μ3-OH)4(NO3)4(O3PBu-t)8(O2CBu-t)16] [CoII4GdIII6(O3PCH2Ph)6(O2CBu-t)14(HO2CBu-t)x(MeCN)y(H2O)z] [CoII6GdIII8(μ3-OH)8(O3PBu-t)6(O2CBu-t)16(H2O)2(MeCN)x](MeCN)y [NiII6GdIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCO2H)2]·(MeCN)4 [NiII6DyIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCO2H)2](MeCN)4 [NiII6YIII6(OH)2(O3PCH2Ph)6(O2CBu-t)16(MeCO2H)2]·(MeCN)4 [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PMe)6(O2CBu-t)16] [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PC6H13-n)6(O2CBu-t)16] [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PPh)6(O2CBu-t)16] [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PC8H17-n)6(O2CBu-t)16] [Ni6Gd6(μ3-OH)2(μ2-OAc)2(O3PCH2Ph)6(O2CBu-t)16] [Fe6Gd6(μ3-O)2(CO3)(O3PMe)6(O2CBu-t)8] [Fe6Gd6(μ3-O)2(CO3)(O3PPh)6(O2CBu-t)8] [Fe6Gd6(μ3-O)2(CO3)(O3PC6H13-n)6(O2CBu-t)8] [Gd8(O3PBu-t)6(μ3-OH)2(H2O)2(HOBu-i)(O2CBu-t)12](NH3Pr-i)2 [Co3(μ3-O)(O2CBu-t)6(py)3][Gd10(O2CBu-t)18(O3PBu-t)6(OH)(H2O)4] a

ΔSm (magnetic entropy change) = R ln(2S + 1). bΔH = applied field.

Scheme 68. Biginelli Reaction Catalyzed by [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4]44

these cases, it is clear that the other ligands that are present are responsible for the overall magnetic behavior. Single-molecule magnets are compounds that are magnetized in the presence of a magnetic field and that retain the magnetization even after the field is switched off, usually below a certain critical temperature. The reader is referred to some leading reviews in this field for further details.353−358 From cumulative data obtained on a large number of complexes, it can now be said that the prerequisites for a compound to exhibit SMM behavior are the presence of a high-spin ground state (S) and a high magnetic anisotropy resulting in a zero-field splitting parameter D.353−359 The combined effect of S and D results in an effective energy barrier energy barrier (Ueff) for the reversal of magnetization as given by the following equations: Ueff = S2|D| and Ueff = (S2 −1/4)|D| for the integer and half integer spin, respectively. The first complex that was shown to possess an SMM behavior is the

mixed-valent dodecanuclear, [MnIV 4 MnIII 8 (μ3 -O) 12 (O 2 CMe) 16(OH2)4]·2MeCO2H·4H2O (Mn12-acetate).360 Since then, several compounds containing 3d, 3d/4f, or 4f metal ions have been shown to exhibit this property. Representative CU


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aspect is that the coordination response of the phosphonate ligands can be modulated by varying the nature of the substituent on phosphorus. These unique features are distinctive in comparison to the carboxylate family and are responsible for the increased use of the phosphonate ligands in the preparation of polynuclear complexes. Although a large body of work has appeared, as evident from the discussion presented above, on various molecular metal phosphonates, it is clear that considerable potential still exists. Thus, a perusal of the literature so far reveals that many metal phosphonates are still completely unknown. Second, many families are still quite sparse. Thus, both lanthanide and actinide phosphonates have not been studied in detail, and there appears to be considerable possibilities in this area. Another interesting possibility is the assembly of metal organic frameworks (MOFs) and 3D-porous structures containing phosphonate ligands.

examples of SMMs containing phosphonate ligands are summarized in Table 27. In addition to SMM properties, polynuclear complexes containing 3d/4f or 4f ions have also attracted attention as magnetic refrigerants. Isotropic clusters with large spin ground states are ideal candidates for displaying an enhanced magnetocaloric effect (MCE) and therefore have been viewed as potential magnetic refrigerants. The reader is referred to recent articles on the principles of magnetic refrigeration.20−25,361−363 Some compounds containing phosphonate ligands, which exhibit MCE, are summarized in Table 28. 19.2. Other Properties

Some of the lanthanide phosphonate complexes are also good catalysts. For example, a dinuclear Ce I II complex, [Ce2{Ph3CPO2(OEt)}4(NO3)2(H2O)4], has been shown to be a very efficient catalyst for the Biginelli reaction involving a three-component condensation reaction between an aldehyde, 1,3-ketoester, and urea (Scheme 68).44 The utility of metal phosphonates in catalysis needs to be explored further. The compounds [Cu 4 (μ-Cl) 2 (μ 3 -C 6 H 11 PO 3 ) 2 (bpy) 4 ]· (NO 3 ) 2 , [Cu 4 (μ-CH 3 CO 2 ) 2 (μ 3 -C 6 H 11 PO 3 ) 2 (2,2-bpy) 4 ]· (CH3CO2)2, [Cu4(μ-OH)(μ3-C6H11PO3)2(2,2-bpy)4(H2O)2]· (NO3)3, and [Cu4(μ-OH)(μ3-C6H11PO3)2(phen)4(H2O)2]· (NO3) have been shown to be very good plasmid modifiers in the presence of external oxidants such as magnesium monoperoxy phthalate (MMPP).283 This aspect also has been confined to these complexes, and it is likely that many other phosphonate complexes may be of use in DNA cleavage studies. Similarly, molybdenum and platinum metal phosphonates also have interesting biological and catalytic activity. The compounds [(C 2 H 5 ) 2 NH 2 ] 4 [Mo V 4 O 8 (O 3 PC(C 3 H 6 NH 3 )OPO3)2]·6H2O, [(C2H5)2NH2]6[MoV4O8(O3PC(C10H14NO)OPO3)2]·18H2O, Li8[(MoV2O4(H2O))4(O3PC(C3H6NH3)OPO 3 ) 4 ]·45H 2 O, Na 2 Rb 6 [(Mo VI 3 O 8 ) 4 (O 3 PC(C 3 H 6 NH 3 )OPO3)4]·26H2O, and [Fc(CH2)nPO3Pt(PPh3)2] (n = 1, 2) have been shown to possess a good antitumor activity.172 Because lanthanide ions such as EuIII or TbIII are photophysically active, complexes [Na6Eu9L16]·(OH)·51H2O (Figure 185) and [Na6Tb9L16]·(OH)·51H2O have been investigated.335 Here, the ligand 5′-methyl-2,2′-bipyridyl-6-phosphonic acid (LH2) has been shown to be a very good sensitizer of EuIII and TbIII luminescence in aqueous solution. An interesting heterometallic IrIII/DyIII phosphonate, [DyIr6(ppy)12(bpp)2(bppH)4]·(CF3SO3)·8H2O [ppyH = 2-phenylpyridine, bpp2− = 2-pyridylphosphonate), shows dual functions, photoluminescence and field-induced slow magnetization relaxation.259 In summary, although potential applications of phosphonate complexes have been demonstrated, particularly in the area of molecular magnetism, there appears to considerable scope of exploration in many other areas.

AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected], [email protected]. Notes

The authors declare no competing financial interest. Biographies

Joydeb Goura obtained his B.Sc. from the Midnapore College, Vidyasagar University, Midnapore, West Bengal, India, in 2007 and M.Sc. degree in 2009 in inorganic chemistry from Vidyasagar University. He completed his Ph.D. at Indian Institute of Technology Kanpur, Kanpur, India, under the supervision of Prof. V. Chandrasekhar. He is currently a postdoctoral research associate at the National Institute of Science Education and Research (NISER), Bhubaneswar. His research interests include molecular magnetism and metal clusters.

20. CONCLUSION From the foregoing discussion on various molecular metal phosphonates, it is clear that the phosphonate family of ligands has found wide applications in the preparation of complexes whose nuclearity varies considerably. The formation of polynuclear complexes becomes possible because of two reasons. First, the coordination capability of the phosphonate ligands ranges from 1.100 to 9.333 (binding up to 7.322 has been achieved, thus far). Second, the phosphonate ligands can stitch up smaller subunits affording larger ensembles. In addition to these two favorable features, another attractive CV


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HPiv NaPiv acacH NEt3 Htea 5-Brsalen

Vadapalli Chandrasekhar was born in Kolkata in November 1958. After his early education at the Osmania University, Hyderabad, he obtained his Ph.D. degree in 1982 from the Indian Institute of Science, Bangalore. He did his postdoctoral work at the University of Massachusetts, Amherst, MA (1983−1986). After briefly working at the Research and Development section of the Indian Petrochemicals Corporation at Vadodara, as a Senior Research Officer, he joined the Department of Chemistry at the Indian Institute of Technology Kanpur in 1987 where he has been a full professor since 1995. He served as the Head of the Department of Chemistry, IIT Kanpur (2008−10), and as the Dean of Faculty Affairs, IIT Kanpur (2011− 12). He also worked at the Tata Institute of Fundamental Research, Centre for Interdisciplinary Sciences, Hyderabad,as a Senior Professor and Dean (2012−14). Currently he is a Director, National Institute of Science Education and Research (NISER), Bhubaneswar, India. His research interests are in the area of molecular materials, inorganic rings and polymers, main-group organometallics, and polynuclear metal assemblies. He has been a recipient of several national and international awards and fellowships. He received the S. S. Bhatnagar Award of the Council and Scientific Industrial Research, India, and the Friedrich-Wilhelm-Bessel Research Award of the Alexander von Humboldt Foundation, Germany. He is an elected Fellow of the Indian Academy of Sciences, Bangalore, the National Academy of Sciences, Allahabad, the Indian National Science Academy, and the Academy of Sciences of the Developing World, Trieste, Italy. He served on the editorial board of several leading journals including the ACS journal, Organometallics.

Lawsson’s reagent THF DMF DME 5pm8hqH3 AIPA 2-PypOH2 4-PypOH2 H3cnp FMPA ampa H4PMIDA (1-NH2-1-C6H10)PO3H2

ACKNOWLEDGMENTS We thank the Department of Science and Technology, India, and the Council of Scientific and Industrial Research, India, for financial support. V.C. is thankful to the Department of Science and Technology for a JC Bose fellowship. J.G. thanks the Council of Scientific and Industrial Research, India, for a Senior Research Fellowship. ABBREVIATIONS PzH Im Phen bipy bpya bipp Bz pip 2-PyPzH 3,5-t-Bu2PzH 3,5-(CF3)2PzH dpzpy H2phpzH 2-PyCl 2-apy Hmhp Hchp en TMEDA Fc OAc HO2CPh-2-Ph

hedpH4 3−Cl-C6H4CH2PO3H2 dtbhpH2 bbimpH2

pivalic acid sodium pivalate acetylacetone triethylamine triethanolamine N,N-ethylenebis(5-bromosalicylideneiminate)dianion [RP(S)(μ-S)]2 (R = 4-anisyl) tetrahydrofuran dimethylformamide 1,2-dimethoxyethane 5-phosphonomethyl-8-hydroxyquinoline phosphonic acid 1-amino-1-methyl-ethylphosphonic acid 2-pyridylphosphonic acid 4-pyridylphosphonic acid 2,6-carboxynaphthalene phosphonic acid, HO3PC10H6CO2H FcCH2PO3H2 aminomethylphosphonic acid N-(phosphonomethyl)iminodiacetic acid 1-amino-1-cyclohexylphosphonic acid 1-hydroxyethylidenediphosphonic acid 3-chlorobenzylphosphonic acid 3,5-di-tert-butyl-2-hydroxybenzylphosphonic acid bis(benzimidazol-2ylmethyl)imino (methylene phosphonic acid)

[{(C7H5N2)CH2}2NCH2PO3H2] H8EDTMP ethylenediaminetetra(methylenephosphonic acid) H5do3ap 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic-10-methylphosphonic acid H2pmp N-piperidinomethane-1phosphonic acid PMAS 2-(phosphonomethyl)-aminosuccinic acid Na2Pam disodium bisphosphonates pami-dronate H4dbp 4,4′-dimethylenebiphenyldiphosphonicacid MDP methylene diphosphonate AEDPH4 1-aminoethylidenediphosphonic acid HPAA hydroxyphosphonoacetic acid HEDP hydroxyethylidene-diphosphonic acid EDPA 1,2-ethanedisphosphonic acid H8BDTMP butylene diamine tetra(methylene phosphonic acid)

pyrazole imidazole 1,10-phenanthroline 2,2′-bipyridine 2,2-bipyridylamine 4,4′-bipyridylpropane benzyl piperidine 2-pyridylpyrazole 3,5-di-tert-butyl pyrazole 3,5-ditrifluoromethylpyrazole 2,6-bis(pyrazol-3-yl)pyridine 3(5)-(2-hydroxyphenyl) pyrazole 2-chloropyridine 2-aminopyridine 6-methyl-2-pyridone 6-chloro-2-hydroxypyridine ethylenediamine tetramethylenethylenediamine (η5-C5H4)Fe(η5-C5H5) acetate 2-biphenylcarboxylic acid CW


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Review

(14) Cabeza, A.; Aranda, M. A. G. Metal Carboxyphosphonates. In Metal Phosphonate Chemistry: From Synthesis to Applications; Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 107−132. (15) Demadis, K. D.; Stavgianoudaki, N. Structural Diversity in Metal Phosphonate Frameworks: Impact on Applications. In Metal Phosphonate Chemistry: From Synthesis to Applications, Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 438− 492. (16) Zheng, L.-M.; Duan, Y. Structural and Magnetic Studies of Cobalt Phosphonates. In Metal Phosphonate Chemistry: From Synthesis to Applications; Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 235−278. (17) Shimizu, G. K. H.; Taylor, J. M.; Dawson, K. W. Metal Organophosphonate Proton Conductors. In Metal Phosphonate Chemistry: From Synthesis to Applications; Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 493−524. (18) Hix, G. B. Luminescent Metal Phosphonate Materials. In Metal Phosphonate Chemistry: From Synthesis to Applications; Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 525− 550. (19) Gopal, K.; Ali, S.; Winpenny, R. E. P. Structural Studies of Paramagnetic Molecular Phosphonates. In Metal Phosphonate Chemistry: From Synthesis to Applications; Clearfield, A., Demadis, K., Eds.; RSC Publishing: Cambridge, UK, 2012; pp 364−419. (20) Zheng, Y.-Z.; Evangelisti, M.; Winpenny, R. E. P. Large Magnetocaloric Effect in a Wells-Dawson Type {Ni6Gd6P6} Cage. Angew. Chem., Int. Ed. 2011, 50, 3692−3695. (21) Zheng, Y.-Z.; Evangelisti, M.; Winpenny, R. E. P. Co-Gd phosphonate complexes as magnetic refrigerants. Chem. Sci. 2011, 2, 99−102. (22) Pineda, E. M.; Tuna, F.; Pritchard, R. G.; Regan, A. C.; Winpenny, R. E. P.; McInnes, E. J. L. Molecular amino-phosphonate cobalt-lanthanide Clusters. Chem. Commun. 2013, 49, 3522−3524. (23) Pineda, E. M.; Tuna, F.; Zheng, Y.-Z.; Winpenny, R. E. P.; McInnes, E. J. L. Wells-Dawson Cages as Molecular Refrigerants. Inorg. Chem. 2013, 52, 13702−13707. (24) Pineda, E. M.; Tuna, F.; Zheng, Y.-Z.; Teat, S. J.; Winpenny, R. E. P.; Schnack, J.; McInnes, E.; Iron, J. L. Lanthanide Phosphonate Clusters: {Fe 6 Ln 6 P 6 } Wells-Dawson like Structures with D 3d Symmetry. Inorg. Chem. 2014, 53, 3032−3038. (25) Zheng, Y.-Z.; Pineda, E. M.; Helliwell, M.; Winpenny, R. E. P. MnII-GdIII Phosphonate Cages with a Large Magnetocaloric Effect. Chem.Eur. J. 2012, 18, 4161−4165. (26) Li, J.-T.; Cao, D.-K.; Akutagawa, T.; Zheng, L.-M. Zn3(4OOCC6H4PO3)2: A polar metal phosphonate with pillared layered structure showing SHG-activity and large dielectric anisotropy. Dalton Trans. 2010, 39, 8606−8608. (27) Zavras, A.; Fry, J. A.; Beavers, C. M.; Talbo, G. H.; Richards, A. F. 2-Pyridylmethylphosphonic acid: a flexible, multi-dentate ligand for metal Phosphonates. CrystEngComm 2011, 13, 3551−3561. (28) Mao, J.-G.; Wang, Z.; Clearfield, A. Synthesis, Characterization, and Crystal Structures of Two Divalent Metal Diphosphonates with a Layered and a 3D Network Structure. Inorg. Chem. 2002, 41, 2334− 2340. (29) Cabeza, A.; Ouyang, X.; Sharma, C. V. K.; Aranda, M. A. G.; Bruque, S.; Clearfield, A. Complexes Formed between Nitrilotris(methylenephosphonic acid) and M2+ Transition Metals: Isostructural Organic-Inorganic Hybrids. Inorg. Chem. 2002, 41, 2325−2333. (30) DeBurgomaster, P.; Liu, H.; O’Connor, C. J.; Zubieta, J. Metalorganophosphonates: hydrothermal synthesis and structures of [Cu(O 3 PC 1 0 H 6 CO 2 H)] and [Cu(bpy)(HO 3 PC 1 0 H 6 CO 2 )] (H2O3PC10H6CO2H = 2,6-carboxynaphthalene phosphonic acid). Inorg. Chim. Acta 2010, 363, 1654−1658. (31) Taylor, J. M.; Mahmoudkhani, A. H.; Shimizu, G. K. H. A Tetrahedral Organophosphonate as a Linker for a Microporous Copper Framework. Angew. Chem., Int. Ed. 2007, 46, 795−798.

1-amino-2-phenylethane1,1-diphosphonic acid 1,1,2,3,3-pentamethyltrimethylenephosphinic acid 2,6-diisopropylphenyl phosphate magneto caloric effect single-molecule magnet 2,4,6-Me3C6H2 2-phenylpyridine 2-pyridylphosphonate 1,3-bis(dimethylamino)-2propanol alendronic acid bis(diphenylphosphino)ethane dicyclopentadiene tetramethysilane lithiumdiisopropylamide diaminocyclohexane

DEDICATION Dedicated to Professors C. N. R. Rao and H. W. Roesky. REFERENCES (1) Zheng, Y.-Z.; Evangelisti, M.; Tuna, F.; Winpenny, R. E. P. Co− Ln Mixed-Metal Phosphonate Grids and Cages as Molecular Magnetic Refrigerants. J. Am. Chem. Soc. 2012, 134, 1057−1065. (2) Baskar, V.; Gopal, K.; Helliwell, M.; Tuna, F.; Wernsdorfer, W.; Winpenny, R. E. P. 3d-4f Clusters with large spin ground states and SMM behavior. Dalton Trans. 2010, 39, 4747−4750. (3) Goura, J.; Liu, J.; Goddard, P.; Chandrasekhar, V. A Direct ThreeComponent Reaction for the Isolation of a Nonanuclear Iron(III) Phosphonate. Eur. J. Inorg. Chem. 2014, 4342−4348. (4) Rao, C. N. R.; Natarajan, S.; Vaidhyanathan, R. Metal Carboxylates with Open Architectures. Angew. Chem., Int. Ed. 2004, 43, 1466−1496. (5) Furukawa, S.; Reboul, J.; Diring, S.; Sumida, K.; Kitagawa, S. Structuring of metal-organic frameworks at the mesoscopic/macroscopic scale. Chem. Soc. Rev. 2014, 43, 5700−5734. (6) Horcajada, P.; Gref, R.; Baati, T.; Allan, P. K.; Maurin, G.; Couvreur, P.; Férey, G.; Morris, R. E.; Serre, C. Metal-Organic Frameworks in Biomedicine. Chem. Rev. 2012, 112, 1232−1268. (7) Brown, H. C.; Braude, E. A.; Nachod, F. C. Determination of Organic Structures by Physical Methods; Academic Press: New York, 1955. (8) Dippy, J. F. J.; Hughes, S. R. C.; Rozanski, A. The Dissociation Constants of Some Symmetrimlly Disubstituted Succinic Acids. J. Chem. Soc. 1959, 2492−2498. (9) Dawson, R. M. C.; et al. Data for Biochemical Research; Clarendon Press: Oxford, 1959. (10) Kumler, W. D.; Eiler, J. J. The Acid Strength of Mono and Diesters of Phosphoric Acid. The n-Alkyl Esters from Methyl to Butyl, the Esters of Biological Importance, and the Natural Guanidine Phosphoric Acids. J. Am. Chem. Soc. 1943, 65, 2355−2361. (11) Freedman, L. D.; Doak, G. O. The Preparation and Properties of Phosphonic Acids. Chem. Rev. 1957, 57, 479−523. (12) Wang, M.; Yuan, D.-Q.; Ma, C.-B.; Yuan, M.-J.; Hu, M.-Q.; Li, N.; Chen, H.; Chen, C.-N.; Liu, Q.-T. The use of phosphonates for constructing 3d-4f clusters at high oxidation states: synthesis and characterization of two unusual heterometallic CeMn complexes. Dalton Trans. 2010, 39, 7276−7285. (13) Coxall, R. A.; Harris, S. G.; Henderson, D. K.; Parsons, S.; Tasker, P. A.; Winpenny, R. E. P. Inter-ligand reactions: in situ formation of new polydentate ligands. J. Chem. Soc., Dalton Trans. 2000, 2349−2356. CX


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