Review pubs.acs.org/Organometallics
Chemistry of Heavier Group 14 Base-Stabilized Heterovinylidenes Wing-Por Leung,*,† Yuk-Chi Chan,†,‡ and Cheuk-Wai So‡ †
Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371
‡
ABSTRACT: This review covers the synthesis, structures, and reactivity of heavier group 14 basestabilized heterovinylidenes featuring a >CE: bond (E = Si, Ge, Sn, Pb). The supporting ligands used in the synthesis of these base-stabilized heterovinylidenes are mainly bulky and bear electron-donating substituents which are essential in coordinating to the metal centers for stabilization. These isolated, thermally stable heavier group 14 metal analogues of vinylidene have been structurally characterized. The structural study of bis(germavinylidene) ((Me3SiNPPh2)2CGe→GeC(PPh2NSiMe3)2) had shown that the Ge−C distances of 1.905(8) and 1.908(7) Å found in the complex are consistent with a Ge−C double bond. The reactivity studies of these heterovinylidenes have been mainly focused on germavinylidenes and stannavinylidenes, as silavinylidenes and plumbavinylidenes are unstable reactive intermediates. The reactivity of bis(germavinylidene), including 1,2-additions, cycloadditions, oxidative additions, ligand-transfer reactions, and Lewis base properties, are described. The reactions of stannavinylidene with various reagents are also described. The results of the reactions of 1,3-diplumbacyclobutane with chalcogens suggested the existence of plumbavinylidene in the solution state. Selected X-ray structures of these base-stabilized heterovinylidenes are shown.
1. INTRODUCTION The chemistry of metal vinylidene complexes (>CCMLn) has received much attention in the past two decades.1 Metal vinylidene complexes have been synthesized, but “free” and stable vinylidene (>CC:) has not been isolated and structurally characterized. Under drastic conditions, the existence of transient “free” vinylidene has been demonstrated.2,3 It is wellknown that vinylidene (1a) is the tautomer of an alkyne (1b) and the rapid rearrangement of β-hydrogen on vinylidene leads to the formation of the corresponding acetylene (Scheme 1).1a
only vinylidene that could be isolated in low-temperature matrices.11,12 The energy barrier for the rearrangement of difluorovinylidene to difluoroacetylene is predicted to be 36.4 kcal/mol; therefore, it is kinetically stable and has been isolated and spectroscopically characterized.12 The reactivity studies of 5 have been performed by using the matrix isolation technique. The reactivity of fluorovinylidene 5 toward various reagents has been reported in the literature.12−17 Another strategy to stabilize reactive vinylidene is by coordinating it to a transition metal. In 1966, Mills et al. reported the first example of the binuclear complex [Fe2(μ-CCPh2)(CO)8] (6) featuring a vinylidene moiety from the reaction of diphenylketene and Fe2(CO)9.18 Mononuclear dicyanovinylidene−molybdenum and −tungsten complexes [(NC)2C CHM(CO)3C5H5] (M = Mo (7), W (8)) have been reported.19 The stabilization of the carbenic carbon in the vinylidene moiety is achieved by donating the lone-pair electrons on the carbon atom to the transition-metal center via a dative bond, together with back-bonding from the filled d orbitals of the transition metal to the carbon atom, which further strengthens the MC bond synergistically.20 The heavier group 14 alkyne analogues disilyne,21 digermyne,22 distannyne,23 and diplumbyne24 have been reported by Sekiguchi and Power et al. All compounds adopt a trans-bent geometry. In contrast to acetylene, substituted heavier alkyne analogues (9a) did not isomerize to the corresponding disilenylidene, digermylidene, distannylidene, or diplumbylidene
Scheme 1
An early example is the pyrolysis or dehydration with carbodiimide of tetrazole derivatives (2, R1 = R2 = H or aryl, X = OH; Scheme 2) to yield acetylene (4). This preliminary result suggested the vinylidene H2CC: (3b) may exist during the rearrangement reaction.2 In another experiment, the migration of the hydrogen or phenyl group to yield phenylacetylene in PhCHC: is further verified from the 13C isotopic labeling experiments.4,5 A computational study of the isomerization of vinylidene to acetylene showed that the process is highly exothermic (−45 kcal/mol), together with having an extremely low activation energy (1.5 kcal/mol);6−8 hence, the lifetime of the vinylidene (∼10−10 s) is extremely short.9 Transient vinylidenes have been detected in matrix experiments and can be trapped by suitable substrates.10 Difluorovinylidene (F2CC:, 5) is the © XXXX American Chemical Society
Special Issue: Mike Lappert Memorial Issue Received: November 12, 2014
A
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics Scheme 2
Scheme 3
Figure 1.
Figure 2. Molecular structure of 14.
(9b), probably owing to the electronic and/or kinetic stabilization of the bulky ligands (Scheme 3). Heterovinylidene (>CE:; E = Si, Ge, Sn, Pb), a heavier group 14 analogue of vinylidene, has rarely been found. The low stability of heterovinylidene could be due to the reduced steric protection at the low-coordinate metal center, which leads to oligomerization, and it is usually treated as a reactive intermediate. Theoretical studies on H2CSi: and H2CGe: suggested that they are relatively stable with respect to the corresponding trans-bent silyne and germyne by ∼3525,26 and 43.4 kcal/mol,27 respectively. Transient H2CSi: and H2CGe: had been detected and studied by laser-induced fluorescence spectroscopy. Jet-cooled H2CSi: and H2CGe: were generated by striking an electric discharge under high-pressure argon seeded with tetramethylsilane or tetramethylgermane vapor.28 Hence, by
Figure 3. Different reactive centers in germavinylidene.
the choice of a proper ligand with suitable electronic and/or kinetic stabilization, group 14 heterovinylidenes can be synthetically accessible. In this review, the recent developments of basestabilized group 14 heterovinylidenes are described.
Scheme 4. Synthesis of Compounds 13 and 14
B
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics Scheme 5. Possible Structures of 14 in Solution State
Scheme 6. Reaction of 14 toward Me3NO and Proposed Mechanism for the Formation of 16
Scheme 7. Reaction of 14 toward Different Chalcogens and Proposed Mechanism for the Formation of 18−20
Scheme 8. Reactions of 14 with Ni(PPh3)4, Pd(PPh3)4, and PdCl2(PPh3)2
(10) have been reported by Baceiredo et al.30 Subsequently, in pioneering work, Frenking et al. performed quantum chemical calculations of the N-heterocyclic carbene (NHC)-stabilized silavinylidene NHCtBu→:CSiR2 (11) at the B3LYP/def2TZVPP level of theory (Figure 1), 31 which suggested that with bulky substituents (R = tBu, NPh 2, Dipp) on the Si
2. SILAVINYLIDENE Compounds containing a >CSi: moiety are considered to be silavinylidenes. No example of monomeric silavinylidene has been reported, although theoretical calculations suggested that 1-silavinylidene or 2-silavinylidene is more stable with respect to trans-bent silyne.29 Recently, phosphane-stabilized silaalkynes C
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics Scheme 9. Reactions of 14 with AgCl and AuI
3. GERMAVINYLIDENE
atom, monomeric NHC-stabilized silavinylidene should be isolable. These molecules feature a linear geometry with a significantly short C−Si bond and have a lower energy than the corresponding silaalkyne complexes, with the exception of R = H.
3.1. Synthesis of Bis(germavinylidene). In 2001, the synthesis of the first stable bis(germavinylidene), [(Me3SiN PPh2)2CGe→GeC(PPh2NSiMe3)2] (14), derived from bis(iminophosphorano)methane was reported.32 Compound 14 can be prepared from the reaction of 2 equiv of [CH(Ph2P NSiMe3)2Li(THF)] (12) with 1 equiv of GeCl2·(1,4-dioxane).32 When the reaction was stopped after 1 day, the heteroleptic chlorogermylene [CH(Ph2PNSiMe3)2GeCl] (13) was isolated, which can be considered as the intermediate for the synthesis of bis(germavinylidene).33 If the reaction mixture was kept for a further 24 h, compound 13 could be further dehydrochlorinated by another 1 equiv of 12 to give bis(germavinylidene) 14. It is suggested that compound 12 behaves as a ligand transfer reagent as well as a base for dehydrochlorination (Scheme 4). Alternatively, [Ge{N(SiMe3)2}2] can also be used as a base for dehydrochlorination of compound 13 to yield bis(germavinylidene).33
Scheme 10. Reactions of 14 toward M(CO)5THF
Scheme 11. Reactions of 14 with CpMn(CO)2THF, Mn2(CO)10, and Cp2V2(CO)5
D
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics Scheme 12. Cycloaddition Reactions of 14 toward Me3SiN3, AdNCO, and Me3SiCHN2
Scheme 13. 1,2-Addition Reactions of 14 toward MnCl2, FeCl2, and [Rh(cod)Cl]2
The X-ray structure analysis revealed that 14 (Figure 2) comprises two germavinylidenes [(Ph2PNSiMe3)2CGe:] bonded together in a head-to-head fashion. The C−Ge bonds (1.905(8) and 1.908(7) Å) are shorter than the C−Ge single bonds in GeII−alkyl or −aryl compounds (2.016−2.347 Å).34 The Ge−Ge bond (2.483(1) Å) is longer than those in reported compounds with a Ge−Ge double bond (2.213−2.347 Å).35 Hence, the Ge−Ge bonding situation in 14 is better described as a donor−acceptor bond. The reactivity of 14 has been investigated by various trapping agents to illustrate that it is a source to generate the reactive monomeric germavinylidene, since the Ge−Ge interaction is weak in solution. In solution state, it is proposed that 14 may exist as bis(germavinylidene) (A), germavinylidene (B), ylide-amide (C), or other oligomers (Scheme 5). It is anticipated that a germavinylidene can behave as a (i) Lewis acid or (ii) Lewis base and undergo (iii) an addition reaction, (iv) an oxidative-addition reaction, or (v) a ligand transfer reaction. The different reactive centers of germavinylidene are shown in Figure 3. 3.2. Reaction of Bis(germavinylidene) with Chalcogens. Attempts to prepare the germaketene analogue containing a >CGeO moiety from the reaction of bis(germavinylidene) 14 with 2 equiv of Me3NO were not successful. Instead, [(μ-N PPh2)(Me3SiNPPh2)CGe(OSiMe3)]2 (16) was isolated. It is proposed that 14 dissociates in solution as the monomeric germavinylidene and reacts with Me3NO to produce the intermediate bearing a >CGeO moiety (15), which then undergoes an insertion of the GeO unit into the N−SiMe3 bond of the imino group to produce compound 16 (Scheme 6).33 Failure to isolate the compound with a terminal >CGeO moiety is probably due to the highly reactive and polarized GeO bond. There is only one example with a GeO bond in which the germanium atom is not stabilized by an electron-donating group.36 Similar reactions by treatment of 14 with stoichiometric amounts of elemental chalcogens afforded the analogous chalcogenbridged dimers of germaketene [(Me3SiNPPh2)2CGe(μ-E)]2 (E = S (18), Se (19), Te (20)) (Scheme 7).33
3.3. Reactions of Bis(germavinylidene) with M(PPh3)4 (M = Ni, Pd). The reaction of 14 with 1 equiv of Ni(PPh3)4 in THF afforded [{(Me3SiNPPh2)2CGe}2Ni(PPh3)2] (21) as dark red crystalline solids. It is suggested that the monomeric germavinylidene generated from 14 in solution behaved as a twoelectron ligand and displaced two PPh3 molecules from Ni(PPh3)4 to form the 18-electron nickel(0) complex 21 (Scheme 8). Treatment of 14 with stoichiometric amounts of Pd(PPh3)4 gave the binuclear 14-electron Pd(0) complex [{(Me3SiNPPh2)2CGe-μ2}Pd(PPh3)]2 (22), featuring two bridging germavinylidene ligands. Compound 22 reacted readily with CH2Cl2 to give PdCl2(PPh3)2 (23) (Scheme 8).37 Similar Lewis basic behavior of germylene has been reported in the reaction of M(PR3)4 (M = Ni, Pd) with [Ge{N(SiMe3)2}2] to give [(R3P)2MGe{N(SiMe3)2}2].38 In addition, the reaction of 14 with PdCl2(PPh3)2 did not afford the adduct complex between Pd and germavinylidene; instead, Pd(PPh3)4 was obtained. The result suggested that germavinylidene acts as a reducing agent. Similar reducing properties of Ge(II) compounds have been reported.39 3.4. Reaction of Bis(germavinylidene) with Group 11 Metal Halides. The reaction of 14 with 2 equiv of AgCl or AuI in THF afforded [(Me3SiNPPh2)2CGeAgCl]2 (24) and [(Me3SiNPPh2)2CGeAuI]2 (25), respectively (Scheme 9). X-ray structures of 24 and 25 show that the germanium atom of germavinylidene moieties insert into the M−X bond to form 24 and 25.37 A similar insertion reaction of a Ge(II) compound into a gold−chlorine bond has been reported.40 The result is also consistent with the theoretical calculation of germylene donor−acceptor complexes with group 11 metal chlorides.41 3.5. Reaction of 14 with Metal Carbonyls. The reaction of 14 with 1 equiv of M(CO)5(THF) in THF afforded the E
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics
[(Me3SiNPPh2)2CGe→Mn(CO)2Cp] (30).43 A similar reaction of 14 with an equimolar amount of Mn2(CO)10 for the longer reaction time of 1 week gave another manganese− germavinylidene complex, [(Me3SiNPPh2)2CGe→Mn(CO)4]2 (31) (Scheme 11).44 The X-ray structures of 30 and 31 show that they both consist of a germavinylidene as a twoelectron ligand bonded to the manganese centers. The reaction of 14 with Cp 2V 2(CO) 5 in THF afforded the vanadium−germacyclopropane complex [(Me3SiN PPh2)2CGeV(CO)2Cp] (32). The “CpV(CO)2” moiety was added across the germanium−carbon double bond of the germavinylidene with concomitant displacement of a CO molecule and formed the three-membered C−Ge−V ring. The formation of 32 is similar to that of 26−28.44 3.6. [2 + n] (n = 2, 3) Cycloaddition Reactions of Bis(germavinylidene) with Organic Substrates. Treatment of 14 with 2 equiv of Me3SiN3, AdNCO (Ad = adamantyl), and Me3SiCHN2 in THF afforded the [2 + 3] cycloaddition product [(Me3SiNPPh2)2CGe{N(SiMe3)NN}] (33), the [2 + 2] cycloaddition product [(Me3SiNPPh2)2CGe{N(Ad)CO}] (34), and the [2 + 3] cycloaddition product [(Me3SiNPPh2)2CGe(NNCHSiMe3)] (35), respectively (Scheme 12).45,46 The X-ray structures of 33−35 show that the Ge−C bond distance increases as the bond order reduced from 2 to 1 by the cycloaddition reactions; these results further support the notion that the germanium−carbon bond in 14 is a GeC bond. 3.7. 1,2-Addition Reactions of Bis(germavinylidene). Treatment of 14 with stoichimetric amounts of transitionmetal chlorides MCl2 (M = Mn, Fe) and [(cod)RhCl]2 (cod = cycloocta-1,5-diene) yielded [(Me3SiNPPh2)2(GeCl)CMn(μ-Cl)]2 (36), [(Me3SiNPPh2)2(GeCl)CFeCl] (37), and [(Me 3 SiNPPh 2 ) 2 {(cod)Rh}CGeCl] (38), respectively (Scheme 13).43,46 The X-ray structural determination of the products obtained show that the M−Cl bond (M = Mn, Fe) adds to the GeC bond of 14 to yield 36 and 37. The formation of 38 is different from those of [RhCl{Ge(NtBu)2SiMe3}4]47 and cis[RhCl{Ge(N(SiMe3)2)2}(PPh3)],48 in which the germylenes act as a Lewis base toward the rhodium center. The reaction of 14 with 2 equiv of (nBu)3SnN3 and the borane−water adduct H2O·B(C6F5)3 in THF gave the 1,2-addition
Scheme 14. 1,2-Addition Reactions of 14 toward (nBu)3SnN3 and B(C6F5)3·H2O
metallagermacyclopropanes [(Me3SiNPPh2)2CGeM(CO)3{M(CO)5}] (M = Cr (26), W (27)).42 The structures of the products as confirmed by X-ray structure analysis suggested that the M(CO)5 moiety added across the germanium−carbon double bond of the germavinylidene moiety with concomitant displacement of two CO molecules, resulting in the three-membered C−Ge−M ring. The germanium atom is also coordinated to another M(CO)5 fragment. A similar reaction of 14 with Mo(CO)5(THF) for a longer time of 3 days afforded the molybdenum carbene complex [(OC) 3 Mo{C(Ph 2 P NSiMe3)2}] (29) together with a small amount of the molybdenum−germacyclopropane [(Me3SiNPPh2)2CGeM(CO)3{M(CO)5}] (28). Germavinylidene generated from 14 behaves as a ligand-transfer reagent in the formation of 29, in which the carbene ligand [:C(Ph2PNSiMe3)2] is being transferred from the germavinylidene to form the metallagermacyclopropane, which is then rearranged with the elimination of “[GeMo(CO)5] (Scheme 10). The reaction of 14 with 2 equiv of CpMn(CO)2(THF) (Cp = η5-C5H5) afforded the manganese germavinylidene complex
Scheme 15. Reaction of 14 with TEMPO and Proposed Mechanism for the Formation of 43
F
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics
suggested that both (nBu)3SnN3 and H2O·B(C6F5)3 underwent a 1,2-addition reaction with 14 in solution, followed by a rearrangement process in which the Ge−C bond was cleaved with the subsequent formation of a Ge−N bond to give the compounds 39 and 40. It is noteworthy that the reaction of 14 with (nBu)3SnN3 contrasts with the result found in the reaction of 14 with Me3SiN3, in which the azide from Me3SiN3 underwent a [2 + 3] cycloaddition reaction. The different results may be due to the fact that the weaker metal−azide bond in (nBu)3SnN3 favors the 1,2-addition. 3.8. Synthesis of Germenes (>CGeCSn bond in 99, which illustrates the nucleophilic character of the Cmethanediide atom in 99. In addition, the reaction of 96 with 2 equiv of AdNCO (Ad = adamantyl) in THF afforded [(PPh2NSiMe3)(PPh2S)C{C(O)N(Ad)}Sn:] (100). It is noteworthy that the lone pair electrons at the tin(II) atom did not undergo a [1 + 2] cycloaddition; instead, the CSn bond undergoes a [2 + 2] cycloaddition to give 100. Similarly, the reaction of 96 with 2 equiv of ArNCO (Ar = 2,6-iPr2C6H3) in THF afforded [(PPh2 NSiMe3)(PPh2S)C−{C(O)N(Ar)}Sn+:] (102, Scheme 36). It is proposed that the reaction proceeds via a [2 + 2] cycloaddition or an insertion reaction to form the intermediate 101, containing a four-membered CSnNC ring.66
2 equiv of [Sn{N(SiMe3)2}2] in refluxing toluene afforded the tin(II) (iminophosphoranyl)(thiophosphoranyl)methanediide [(PPh2NSiMe3)(PPh2S)CSn:]2 (96), which can be considered as a base-stabilized stannavinylidene derivative. However, the reaction of 94 with 2 equiv of [Sn{N(SiMe3)2}2] in toluene at room temperature only gave [HC{(PPh2NSiMe3)(PPh2 S)}SnN(SiMe3)2] (95), together with a small amount of 96. It is suggested that compound 95 was dehydroaminated by [Sn{N(SiMe3)2}2] in refluxing toluene to yield 96 (Scheme 34).63 The molecular structure of 96 (Figure 8) reveals that it is symmetric and consists of two stannavinylidene moieties [(PPh2NSiMe3)(PPh2S)CSn:] bonded in a head-to-head fashion. The presence of a stereoactive lone pair at the tin atom is confirmed by the sum of the angles (258.08°). The C1−Sn1 bond (2.209(9) Å) is significantly shorter than that in 92 (2.384(4) Å). However, it is longer than those in the stannaethene [{(Me3Si) 2CH}2SnC{(BtBu)2C(SiMe3)2}] (2.025(4) Å)64 and 6-stannapentafulvene [(Tbt)(Mes)Sn CR2] (2.016(5) Å),65 which is due to the lower oxidation state of the tin atom in 93. The natural bond orbital (NBO) analysis of 93 suggests that the Sn1−C1 bond is polar and covalent, which is stabilized by the lone-pair electrons on the N and S atoms from the ligand. Furthermore, its bond nature is between a single and double bond. 4.6. Reaction of Stannavinylidene with Sulfur. The reaction of 96 with elemental sulfur in toluene afforded [{(μ-S)SnIVC(PPh2NSiMe3)(PPh2S)}3SnII(μ3-S)] (97) and 94 (Scheme 35). Compound 97 comprises a SnII moiety coordinated
5. PLUMBAVINYLIDENE 5.1. Formation of 1,3-Diplumbacyclobutane from Plumbavinylidene. Until now, no stable plumbavinylidene has been synthesized. Theoretical calculations on triply bonded plumbaalkyne (RCPbR) showed that with smaller substituents (R = F, H, OH, CH 3, SiMe 3) the 1-plumbavinylidene P
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics
“plumbavinylidene” is shown by the reaction with chalcogens. Thermally stable base-stabilized germavinylidene and stannavinylidene bearing bulky ligands with coordinating substituents can be isolated and structurally characterized. Reactions with these heterovinylidenes have shown that they exist in solution and can behave as (i) a Lewis acid or (ii) a Lewis base and undergo (iii) an addition reaction, (iv) an oxidative-addition reaction or (v) a ligand transfer reaction. Theoretical calculations on monomeric NHCstabilized silavinylidenes suggested that they are more stable with respect to the corresponding silaalkynes. It is anticipated, by using an NHC as a supporting ligand, other monomeric group 14 heterovinylidenes should be synthetically accessible in the future.
[R2CPb:] is more stable with respect to 2-plumbavinyldiene [R2PbC:] and trans-bent plumbaalkyne. However, with bulkier substituents (R = Tbt, Ar*, SiMe(SitBu3)2, SiiPr(Dis)2), trans-bent plumbaalkyne is both kinetically and thermodynamically stable.67 Though plumbavinylidene has not been reported, 1,3-diplumbacyclobutane is believed to be the head-to-tail cycloaddition product from the reactive plumbavinylidene. The reactions of 2 equiv of lithium methanide 12, 58, or 59 with 1 equiv of PbCl2 afforded the 1,3-diplumbacyclobutanes 1,3[Pb{μ2-C(Ph2PNSiMe3)2]2 (103), 1,3-[Pb{μ2-C(iPr2P NSiMe 3 )(2-Py)}] 2 (104), and 1,3-[Pb{μ 2 -C( i Pr 2 PS)(C9H6N-2)]2 (105), respectively (Scheme 37). The mechanism for the formation of 103−105 is similar to that of 1,3-digermaand 1,3-distannacyclobutanes, which is believed to be via the unstable plumbavinylidene intermediate. Compounds 102−105 crystallized as steplike structures. Reactions of CH2(Ph2PNSiMe3)2 (68), CH2(Ph2PS)2 (69), {CH2(iPr2PS)}2-C5H3N-2 (70), and CH2(iPr2P S)C9H6N-2 (72) with 1 equiv of Pb{N(SiMe3)2}2 in toluene afforded the 1,3-diplumbacyclobutanes 1,3-[Pb{μ2-C(Ph2P NSiMe3)2]2 (106),32 1,3-[Pb{μ2-C(Ph2PS)2]2 (107),59 [{2{Sn{C(iPr2PS)}}-6-{CH2(iPr2PS)}}C5H3N)]2 (108),60 and 1,3-[Pb{μ2-C(iPr2PS)(C9H6N-2)]2 (109),58 respectively (Scheme 38). The mechanism for the formation of 106−109 is similar to that of 1,3-distannacyclobutane. It is proposed that the reactions proceed through the unstable plumbavinylidenes [:PbC(iPr2PX)(R)] (110) with the elimination of 2 equiv of hexamethyldisilazane, followed by a head-to-tail cyclodimerization to form the 1,3-diplumbacyclobutane. 5.2. Reaction of 1,3-Diplumbacyclobutane with Sulfur and Selenium. Treatment of 107 with stoichiometric amounts of elemental sulfur or selenium in toluene did not give group 14 ketone or ketene analogues (R2PbE or >CPbE; E = S, Se). Instead, the two novel lead(II) chalcogenate complexes [PbE{C(Ph2PS)2}] (E = S (111), Se (112); Scheme 39) were
■
AUTHOR INFORMATION
Corresponding Author
*W.-P.L.: E-mail,
[email protected]; fax, +852 2603 5057. Notes
The authors declare no competing financial interest. Biographies
Wing-Por Leung obtained his B.Sc.(Hons) in Chemistry at the University of Kent (1979), his M.Sc. in Organometallic Chemistry at the University of Sussex (1980), and his Ph.D. at the University of Western Australia (1984) under the supervision of Professor Colin Raston. After his Ph.D., he joined Professor Michael Lappert’s group in Sussex as a Postdoctoral Fellow in 1985. He then took up a lectureship in the Department of Chemistry, The Chinese University of Hong Kong, in 1990. He is currently a Professor in the Department of Chemistry, The Chinese University of Hong Kong. His research interests are in the synthetic, structural, and mechanistic studies of organometallic compounds of early transition metals and group 14 metals.
Scheme 39. Reactions of 104 with Sulfur and Selenium
obtained. It is proposed that compound 107 dissociates into plumbavinylidene in solution and the chalcogen atom inserts into the CPb: bond to form the >C−E−Pb: moiety.59 The result differs from the synthesis of group 14 dialkylmetal chalcogenones R2ME (R = CH(SiMe3)C9H6N-8, CPh(SiMe3)C5H4N-2; M = Ge, Sn)68 and chalcogen-bridged dimers of germaketene analogues 18−20 from bis(germavinylidene).33 This may be explained by the “inert-pair effect”, which makes the electron pair on the lead(II) atom less favorable for bond formation. The 31P NMR spectra of 111 and 112 displayed two singlets at δ 31.87, 57.73 and δ 31.86, 59.39 ppm, suggesting that the two phosphorus nuclei are nonequivalent and may exist as a zwitterion in the solution state (Scheme 39).
6. SUMMARY AND FUTURE PERSPECTIVE Group 14 heterovinylidenes are very reactive and unstable compounds. Stable silavinylidene and plumbavinylidene have not been isolated or structurally characterized. The existence of
Yuk-Chi Chan received his B.Sc. (2008) and Ph.D. (2013) at the Chinese University of Hong Kong under the supervision of Prof. W.-P. Leung. He then joined Nanyang Technological University as a Research Q
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics
(9) Stanton, J. F.; Gauss, J. J. Chem. Phys. 1994, 101, 3001. (10) (a) Norstrom, R. J.; Gunning, H. E.; Strausz, O. P. J. Am. Chem. Soc. 1976, 98, 1454. (b) Sharp, K. G.; Schwager, I. Inorg. Chem. 1976, 15, 1697. (11) Burger, H.; Sommer, S. J. Chem. Soc., Chem. Commun. 1991, 456. (12) Breidung, J.; Bürger, H.; Kötting, C.; Kopitzky, R.; Sander, W.; Senzlober, M.; Thiel, W.; Willner, H. Angew. Chem., Int. Ed. Engl. 1997, 36, 1983. (13) Kötting, C.; Sander, W.; Breidung, J.; Thiel, W.; Senzlober, M.; Bürger, H. J. Am. Chem. Soc. 1998, 120, 219. (14) Kötting, C.; Sander, W.; Senzlober, M. Chem. Eur. J. 1998, 4, 2360. (15) Kötting, C.; Sander, W.; Senzlober, M.; Bürger, H. Chem. Eur. J. 1998, 4, 1611. (16) Kötting, C.; Sander, W. J. Am. Chem. Soc. 1999, 121, 8891. (17) Sander, W.; Kötting, C. Chem. Eur. J. 1999, 5, 24. (18) Mills, O. S.; Redhouse, A. D. Chem. Commun. 1966, 444. (19) King, R. B.; Saran, M. S. J. Am. Chem. Soc. 1972, 94, 1784. (20) Bruce, M. I. Chem. Rev. 1998, 98, 2797. (21) (a) Wiberg, N.; Niedermayer, W.; Fischer, G.; Nöth, H.; Suter, M. Eur. J. Inorg. Chem. 2002, 2002, 1066. (b) Sekiguchi, A.; Kinjo, R.; Ichinohe, M. Science 2004, 305, 1755. (22) Stender, M.; Phillips, A. D.; Wright, R. J.; Power, P. P. Angew. Chem., Int. Ed. 2002, 41, 1785. (23) Phillips, A. D.; Wright, R. J.; Olmstead, M. M.; Power, P. P. J. Am. Chem. Soc. 2002, 124, 5930. (24) Pu, L.; Twamley, B.; Power, P. P. J. Am. Chem. Soc. 2000, 122, 3524. (25) Nguyen, M. T.; Sengupta, D.; Vanquickenborne, L. G. Chem. Phys. Lett. 1995, 244, 83. (26) Stegmann, R.; Frenking, G. J. Comput. Chem. 1996, 17, 781. (27) Stogner, S. M.; Grev, R. S. J. Chem. Phys. 1998, 108, 5458. (28) Harper, W. W.; Ferrall, E. A.; Hilliard, R. K.; Stogner, S. M.; Grev, R. S.; Clouthier, D. J. J. Am. Chem. Soc. 1997, 119, 8361. (29) Lu, T.; Hao, Q.; Wilke, J. J.; Yamaguchi, Y.; Fang, D.-C.; Schaefer, H. F., III J. Mol. Struct. 2012, 1009, 103. (30) Gau, D.; Kato, T.; Saffon-Merceron, N.; De Cózar, A.; Cossío, F. P.; Baceiredo, A. Angew. Chem., Int. Ed. 2010, 49, 6585. (31) Xu, J.; Ding, Y.-H.; Andrada, D. M.; Frenking, G. Chem. Eur. J. 2014, 20, 9216. (32) Leung, W.-P.; Wang, Z.-X.; Li, H.-W.; Mak, T. C. W. Angew. Chem., Int. Ed. 2001, 40, 2501. (33) Leung, W.-P.; So, C.-W.; Wang, Z.-X.; Wang, J.-Z.; Mak, T. C. W. Organometallics 2003, 22, 4305. (34) (a) Hitchcock, P. B.; Lappert, M. F.; Miles, S. J.; Thorne, A. J. J. Chem. Soc., Chem. Commun. 1984, 480. (b) Drost, C.; B. Hitchcock, P.; F. Lappert, M.; J.-M. Pierssens, L. Chem. Commun. 1997, 1141. (c) Simons, R. S.; Pu, L.; Olmstead, M. M.; Power, P. P. Organometallics 1997, 16, 1920. (35) Baines, K. M.; Stibbs, W. G. Coord. Chem. Rev. 1995, 145, 157. (36) Li, L.; Fukawa, T.; Matsuo, T.; Hashizume, D.; Fueno, H.; Tanaka, K.; Tamao, K. Nat. Chem. 2012, 4, 361. (37) Leung, W.-P.; So, C.-W.; Kan, K.-W.; Chan, H.-S.; Mak, T. C. W. Organometallics 2005, 24, 5033. (38) (a) Bender, J. E.; Shusterman, A. J.; Banaszak Holl, M. M.; Kampf, J. W. Organometallics 1999, 18, 1547. (b) Cygan, Z. T.; Bender, J. E.; Litz, K. E.; Kampf, J. W.; Banaszak Holl, M. M. Organometallics 2002, 21, 5373. (39) Hitchcock, P. B.; Lappert, M. F.; Misra, M. C. J. Chem. Soc., Chem. Commun. 1985, 863. (40) Bauer, A.; Schmidbaur, H. J. Am. Chem. Soc. 1996, 118, 5324. (41) Boehme, C.; Frenking, G. Organometallics 1998, 17, 5801. (42) Leung, W.-P.; So, C.-W.; Wang, J.-Z.; Mak, T. C. W. Chem. Commun. 2003, 248. (43) Leung, W.-P.; So, C.-W.; Kan, K.-W.; Chan, H.-S.; Mak, T. C. W. Inorg. Chem. 2005, 44, 7286. (44) Leung, W.-P.; Kan, K.-W. Unpublished results. (45) Leung, W.-P.; Kan, K.-W.; So, C.-W.; Mak, T. C. W. Appl. Organomet. Chem. 2007, 21, 814.
Fellow in Prof. C.-W. So’s group. His current project is focused on the synthesis and reactivity study of low-valent group 14 compounds.
Cheuk-Wai So obtained his Ph.D. in 2003 under the guidance of Prof. W.-P. Leung at The Chinese University of Hong Kong. From 2005 to 2007, he was an Alexander von Humboldt research fellow at the University of Göttingen under the supervision of Prof. Herbert W. Roesky. Then, he was a JSPS research fellow at Nagoya University under the guidance of Prof. Shigehiro Yamaguchi. Since 2008, he has been an Assistant Professor at Nanyang Technological University, Singapore. His research area focuses on the synthesis of novel main-group organometallic complexes and their application in electronic materials and small-molecule activation.
■
ACKNOWLEDGMENTS This review is devoted to the memory of Professor Michael F. Lappert, who was the mentor of W.-P.L. Some of the work described in this review was supported by the Chinese University of Hong Kong (Direct Grant), The Hong Kong Research Grant Council (GRF), and Academic Research Fund Tier 1 of Nanyang Technological University, Singapore.
■
REFERENCES
(1) (a) Bruce, M. I.; Swincer, A. G. Adv. Organomet. Chem. 1983, 22, 59. (b) Bruce, M. I. Chem. Rev. 1991, 91, 197. (c) Beckhaus, R. Angew. Chem., Int. Ed. Engl. 1997, 36, 687. (d) Bruneau, C.; Dixneuf, P. H. Acc. Chem. Res. 1999, 32, 311. (e) Puerta, M. C.; Valerga, P. Coord. Chem. Rev. 1999, 193−195, 977. (f) Lin, Y. C. J. Organomet. Chem. 2001, 617− 618, 141. (g) Knorr, R. Chem. Rev. 2004, 104, 3795. (h) Selegue, J. P. Coord. Chem. Rev. 2004, 248, 1543. (i) Valyaev, D. A.; Semeikin, O. V.; Ustynyuk, N. A. Coord. Chem. Rev. 2004, 248, 1679. (j) Wakatsuki, Y. J. Organomet. Chem. 2004, 689, 4092. (k) Werner, H. Coord. Chem. Rev. 2004, 248, 1693. (l) Bruneau, C.; Dixneuf, P. H. Angew. Chem., Int. Ed. 2006, 45, 2176. (m) Varela, J. A.; Saa, C. Chem. Eur. J. 2006, 12, 6450. (n) Antonova, A. B. Coord. Chem. Rev. 2007, 251, 1521. (o) Trost, B. M.; McClory, A. Chem. Asian J. 2008, 3, 164. (2) Behringer, H.; Matner, M. Tetrahedron Lett. 1966, 7, 1663. (3) Brown, R. F. C.; Harrington, K. J. J. Chem. Soc., Chem. Commun. 1972, 1175. (4) Brown, R. F. C.; Harrington, K. J.; McMullen, G. L. J. Chem. Soc., Chem. Commun. 1974, 123. (5) Brown, R. F. C.; Eastwood, F. W.; Jackman, G. P. Aust. J. Chem. 1978, 31, 579. (6) (a) Osamura, Y.; Schaefer, H. F.; Gray, S. K.; Miller, W. H. J. Am. Chem. Soc. 1981, 103, 1904. (b) Gallo, M. M.; Hamilton, T. P.; Schaefer, H. F. J. Am. Chem. Soc. 1990, 112, 8714. (7) Petersson, G. A.; Tensfeldt, T. G.; Montgomery, J. A. J. Am. Chem. Soc. 1992, 114, 6133. (8) (a) Pople, J. A.; Raghavachari, K.; Frisch, M. J.; Binkley, J. S.; Schleyer, P. V. R. J. Am. Chem. Soc. 1983, 105, 6389. (b) Chang, N.-y.; Shen, M.-y.; Yu, C.-h. J. Chem. Phys. 1997, 106, 3237. R
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
Review
Organometallics (46) Leung, W.-P.; Kan, K.-W.; Chan, Y.-C.; Mak, T. C. W. Inorg. Chem. 2013, 52, 4571. (47) Veith, M.; Müller, A.; Stahl, L.; Nötzel, M.; Jarczyk, M.; Huch, V. Inorg. Chem. 1996, 35, 3848. (48) Lappert, M. F.; Rowe, R. S. Coord. Chem. Rev. 1990, 100, 267. (49) Leung, W.-P.; Kan, K.-W.; So, C.-W.; Mak, T. C. W. Organometallics 2007, 26, 3802. (50) Iwamoto, T.; Masuda, H.; Ishida, S.; Kabuto, C.; Kira, M. J. Am. Chem. Soc. 2003, 125, 9300. (51) Tokitoh, N.; Manmaru, K.; Okazaki, R. Organometallics 1994, 13, 167. (52) Litz, K. E.; Bender, J. E.; Sweeder, R. D.; Banaszak Holl, M. M.; Kampf, J. W. Organometallics 2000, 19, 1186. (53) Barrau, J.; Rima, G.; El, A. Organometallics 1998, 17, 607. (54) (a) Khan, S.; Sen, S. S.; Michel, R.; Kratzert, D.; Roesky, H. W.; Stalke, D. Organometallics 2011, 30, 2643. (b) Azhakar, R.; Roesky, H. W.; Wolf, H.; Stalke, D. Organometallics 2012, 31, 8608. (55) Veith, M.; Mathur, C.; Huch, V. J. Chem. Soc., Dalton Trans. 1997, 995. (56) Leung, W.-P.; Chiu, W.-K.; Mak, T. C. W. Inorg. Chem. 2013, 52, 9479. (57) Leung, W.-P.; Wang, Z.-X.; Li, H.-W.; Yang, Q.-C.; Mak, T. C. W. J. Am. Chem. Soc. 2001, 123, 8123. (58) Leung, W.-P.; Chan, Y.-C.; Mak, T. C. W. Organometallics 2013, 32, 2584. (59) Leung, W.-P.; Wan, C.-L.; Kan, K.-W.; Mak, T. C. W. Organometallics 2010, 29, 814. (60) Leung, W.-P.; Kan, K.-W.; Mak, T. C. W. Organometallics 2010, 29, 1890. (61) Yang, Y.-F.; Foo, C.; Ganguly, R.; Li, Y.; So, C.-W. Organometallics 2012, 31, 6538. (62) Yang, Y.-F.; Ganguly, R.; Li, Y.; So, C.-W. Organometallics 2013, 32, 2643. (63) Guo, J.; Lau, K.-C.; Xi, H.-W.; Lim, K. H.; So, C.-W. Chem. Commun. 2010, 46, 1929. (64) Meyer, H.; Baum, G.; Massa, W.; Berger, S.; Berndt, A. Angew. Chem., Int. Ed. Engl. 1987, 26, 546. (65) Mizuhata, Y.; Takeda, N.; Sasamori, T.; Tokitoh, N. Chem. Commun. 2005, 5876. (66) Guo, J.-Y.; Li, Y.; Ganguly, R.; So, C.-W. Organometallics 2012, 31, 3888. (67) Wu, P.-C.; Su, M.-D. Organometallics 2011, 30, 3293. (68) Leung, W.-P.; Kwok, W.-H.; Zhou, Z.-Y.; Mak, T. C. W. Organometallics 2000, 19, 296.
S
DOI: 10.1021/om5011403 Organometallics XXXX, XXX, XXX−XXX
