Polynuclear Complexes of Ligands Containing in Situ Formed

Article pubs.acs.org/crystal

Polynuclear Complexes of Ligands Containing in Situ Formed Oxazinane and Oxazolidine Rings with Appended Alkoxyl and Phenol Groups Caixia Ding,† Fanhua Zeng,†,‡ Jia Ni,§ Bingwu Wang,*,# and Yongshu Xie*,† †

Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science & Technology, Shanghai 200237, P. R. China ‡ Department of Chemistry and Life Sciences, Xiangnan University, Chenzhou 423000, P. R. China § Department of Chemistry, Shantou University, Shantou, 515063, P. R. China # Beijing National Laboratory of Molecular Science, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China S Supporting Information *

ABSTRACT: In situ formation of ligands is an efficient approach to synthesizing novel complexes with unique coordinating moieties. Oxazolidines and oxazinanes are 1,3-N,O-containing five-membered and six-membered heterocycles, respectively. Metal complexes of ligands derived from these two heterocycles are rather rare. In this work, we designed and synthesized a novel multihydoxy ligand, 2((2,3-dihydroxypropylamino)methyl)phenol (H3L1). It contains both aminoethanol and aminopropanol units, which may be employed to react with aldehydes to afford oxazolidines and oxazinanes, respectively. Thus, H3L1 was reacted with metal salts in the absence or presence of aldehydes to afford complexes [Cu(HL1)]2 (1), [CuL2]4·4CH3OH (2) [Zn5Na2(L3)4(DMSO)2.65(DMF)1.35]·DMF (3), and [Ni(HL4)]2 (4). Complex 1 is a dialkoxo-bridged binuclear Cu(II) complex. The coordination moieties are linked by intermolecular C−H···O hydrogen bonds to afford a 1D double-chain supramolecular structure. Interestingly, in complexes 2−4, H3L1 has been reacted with formaldehyde, salicylaldehyde, and 2,6-diformyl-4-cresol to afford novel ligands H2L2, H3L3, and H3L4, respectively. The combination of in situ formed oxazinane or oxazolidine rings with appended alkoxyl and phenol functionalities in these ligands has been demonstrated to form a rich diversity of coordination structures. Thus, 2 is a tetranuclear Cu(II) complex with a face-sharing double defective cubane core structure. In this complex, (L2)2− ligands coordinate in two different bridging modes with the Harris notations of 3.1121221311 and 3.1131231111, respectively. Complex 3 has an interesting heptanuclear Zn5Na2 core structure. A central Zn(II) is coordinated with four alkoxo O atoms from four (L3)3− ligands. Each of the O atom further bridges another Zn(II) atom, resulting in a Zn5 moiety, which is then connected to two Na+ by phenoxo O bridges, finally affording the Zn5Na2 core. The bridging mode of (L3)3− can be designated as 4.21221311312411. And Complex 4 is a binuclear Ni(II) complex containing di-μ2-phenoxo bridges. The coordination moieties are linked by intermolecular C−H···π, C−H···O, and π···π interactions to afford a two-dimensional supramolecular network. These results indicate that the combination of in situ formed oxazinane and oxazolidine rings with appended phenol and alkoxyl functionalities is an efficient approach to developing novel ligands and complexes with a rich structural diversity. Variable temperature magnetic data measurements revealed that medium antiferromagnetic interaction exists between the Cu(II) centers in complex 1 with a −2J value of 278 cm−1. And in complex 4, weak antiferromagnetic coupling occurs between the Ni(II) centers, with a −2J value of 9.36 cm−1.

■

INTRODUCTION Polynuclear complexes contain multimetal centers connected by endogenous or exogenous bridges. They have attracted intense interest due to their biological relevance, aesthetic appeal and the importance in the synthesis of novel molecular magnets with desired coupling interactions between the metal centers.1−3 The design, synthesis and utilization of novel polydentate ligands with endogenous bridging and chelating groups has been demonstrated to be one of the most efficient approaches to synthesizing such complexes.4 Thus, alkoxyl, © 2012 American Chemical Society

phenol and carboxyl groups have been utilized as common bridging groups.5−7 Regarding the chelating moieties, aromatic heterocycles, such as pyridine and quinoline, have been widely utilized.8,9 In contrast, saturated heterocycles have attracted much less attention. Oxazolidines and oxazinanes are 1,3-N,Ocontaining five-membered and six-membered saturated heteroReceived: January 22, 2012 Revised: February 24, 2012 Published: March 10, 2012 2089

dx.doi.org/10.1021/cg300096n | Cryst. Growth Des. 2012, 12, 2089−2096

Crystal Growth & Design

Article

added in portions, and the resulting mixture was refluxed for 2 h, meanwhile the color changed slowly from yellow to colorless. A white precipitate of 2-((2,3-dihydroxypropylamino)methyl)phenol was obtained (9.5 g, 48.2%). 1H NMR (DMSO-d6, Bruker 500 MHz): 7.06 (t, 2H, Ar−H), 6.68−6.72 (m, 2H, Ar−H), 3.85 (d, J = 14.0 Hz, 1H, ArCH2), 3.79 (d, J = 14.0 Hz, 1H, ArCH2), 3.54−3.58 (m, 1H, CH2CHOH), 3.34 (dd, J1 = 11.0 Hz, J2 = 6.0 Hz, 1H, NHCH2CH), 3.27 (dd, J1 = 11.0 Hz, J2 = 6.0 Hz, 1H, NHCH2CH), 2.61 (dd, J1 = 12.0 Hz, J2 = 4.0 Hz, 1H, CHCH2OH), 2.43 (dd, J1 = 12.0 Hz, J2 = 7.5 Hz, 1H, CHCH2OH). IR (KBr, cm−1): 3311 (br), 3120 (s), 2943 (m), 1608 (m), 1582 (m), 1491 (s), 1462 (s), 1447 (s), 1389 (m), 1330 (m), 1278 (s), 1241 (s), 1208 (s), 1116 (s), 1075 (s), 1037 (s), 1013 (s), 904 (m), 857 (m), 799 (m), 762 (s), 645 (w), 580 (w), 540 (w), 496 (w), 474 (w). [Cu(HL1)]2 (1). To a methanol solution containing H3L1 (158 mg, 0.8 mmol) and Cu(NO3)2·3H2O (193.2 mg, 0.8 mmol) was added aqueous NaOH (0.4 mL, 4 M, 1.6 mmol) dropwise with stirring. After refluxing for 3 h, The resulting solution was concentrated in vacuo to 20 mL, filtered, and left undisturbed at room temperature for several days, yielding platelike dark green single crystals of 1 suitable for X-ray diffraction analysis. Yield: 85 mg, 41%. Anal. Calcd for C20H26Cu2N2O6: C, 46.42, H, 5.06, N, 5.41. Found C, 46.42, H, 5.25, N, 5.33. IR (KBr, cm−1): 3440(s), 3230(s), 2923(m), 2855(m), 2360(w), 1634(w), 1594(s), 1539(w), 1481(vs), 1455(vs), 1302(vs), 1120(s), 1082 (s), 1065 (s), 1006 (s), 993 (m), 880 (m), 770 (w), 650 (w), 597 (w). [CuL2]4·4CH3OH (2). CuCl2·2H2O (70 mg, 0.4 mmol), H3L1 (79 mg, 0.4 mmol), aqueous NaOH (0.3 mL, 4 M, 1.2 mmol) and formalin (30 μL, 0.4 mmol) were added successively to methanol (50 mL). The resulting solution was refluxed for 3 h, and then concentrated in vacuo to approximately 20 mL, filtered, and left undisturbed at room temperature for several days, yielding platelike dark green single crystals of 2 suitable for X-ray diffraction analysis. Yield: 20.6 mg, 19%. Anal. Calcd for (C48H68Cu4N4O16) (%): C, 47.60, H, 5.66, N, 4.63. Found C, 47.81, H, 5.62, N, 4.78. IR (KBr, cm−1): 3419(b), 2910(w), 2853(w), 1634(w), 1594.90(s), 1478(vs), 1452(s), 1297(s), 1278(s), 1205(m), 1168(m), 1139(m), 1081(m), 1056(s), 1034(m), 977(m), 883(m), 872(s), 834(w), 791(w), 755(w), 572(s), 480(w). [Zn5Na2(L3)4(DMSO)2.65(DMF)1.35]·DMF (3). A mixture of H3L1 (9.9 mg, 0.05 mmol), salicylaldehyde (6.1 mg, 0.05 mmol), ZnCl2·2H2O (8.6 mg, 0.05 mmol), and aqueous NaOH (0.1 mL, 2 M, 0.2 mmol) in DMF, DMSO and H2O (6:10:1) was sealed in a vial (10 mL), which was heated to 120 °C for 120 h. After the mixture was cooled to room temperature, yellow block crystals of 3 suitable for X-ray structure determination were obtained. Yield: 3 mg, 12% based on H3L1. Anal. Calcd for C80.35H96.35N6.35Na2O21S2.65Zn5: C, 49.62; H, 4.99; N, 4.57. Found C, 49.49; H, 5.18; N, 4.37. IR (KBr, cm−1): 3441(br), 2963(m), 2922(m), 2847(m), 1560(s), 1481(s), 1455(m), 1384(m), 1312(w), 1275(s), 1129(m), 1084(m), 1045 (m), 981 (s), 914 (w), 873 (w), 753 (w), 543 (m), 490 (m). [Ni(HL4)]2 (4). A mixture of H3L1 (4.0 mg, 0.02 mmol), 2,6diformyl-4-cresol (1.6 mg, 0.01 mmol), Ni(OAc)2·4H2O (5.0 mg, 0.02 mmol), in DMF and H2O (9: 1) was sealed in a vial (10 mL), which was heated to 120 °C for 120 h. After the mixture was cooled to room temperature, dark green block crystals of 4 suitable for X-ray structure determination were obtained. Yield: 2 mg, 50% based on 2,6-diformyl4-cresol. Anal. Calcd for C38H38N2Ni2O10: C, 57.04; H, 4.79; N, 3.50. Found C, 56.75; H, 4.89; N, 3.81. IR (KBr, cm−1): 3427(br), 2972(m), 2924(m), 2850(m), 1628(vs), 1595(m), 1549(s), 1481(s), 1453(s), 1402(s), 1339(m), 1286(m), 1223(w), 1111(s), 1082(m), 1041(m), 996(m), 978(s), 874(w), 836(w), 756(w), 586(m). X-ray Crystallography. X-ray diffraction data were collected on a Bruker-AXS APEX or an Oxford Diffraction Gemini S Ultra diffractometer utilizing MoKα radiation (λ = 0.71073 Å). The structures were solved by direct methods and refined with full-matrix least-squares technique. Anisotropic thermal parameters were applied to all non hydrogen atoms. All of the hydrogen atoms in these structures are located from the differential electron density map and

cycles, respectively. Various conditions have been employed to synthesize these moieties by the reaction of aldehydes with aminoethanols and aminopropanols, respectively.10 A few mononuclear coordination compounds of ligands containing these heterocyles have been reported.11 Recently, Das and co-workers reported binuclear complexes of oxazolidine and oxazinane derived ligands, which formed in situ by serendipity.12 In fact, in situ formation of ligands is an efficient approach to synthesizing interesting polynuclear complexes containing unique coordinating moieties that may be rather difficult to access by other methods.13 Based on this background, and in continuation of our previous work on polynuclear complexes of multihydroxyl aminophenol ligands and other related complexes,14 we herein first synthesized a novel multihydoxy ligand, 2-((2,3-dihydroxypropylamino)methyl) phenol (H3L1) and its binuclear Cu(II) complex, [Cu(HL1)]2 (1). Considering the fact that H3L1 contains both aminoethanol and aminopropanol units, which may react with aldehydes to afford either oxazolidines or oxazinanes, H3L1 was reacted with metal salts in the presence of various aldehydes to afford complexes [CuL2]4·4CH3OH (2), [Zn5Na 2(L3)4(DMSO)2.65(DMF)1.35]·DMF (3), and [Ni(HL4)]2 (4). In these complexes, H3L1 has been demonstrated to react with formaldehyde, salicylaldehyde, or 2,6-diformyl-4-cresol to form oxazinane or oxazolidine rings with appended alkoxyl and phenol groups. Combination of the in situ formed heterocycles and the appended functionalities has been demonstrated to form a rich diversity of coordination compounds with the coordination core structures varying from Ni(II)2, Cu(II)4 to Zn(II)5Na(I)2. The results indicate that the combination of H3L1 with various aldehydes and metal salts is effective for the syntheses of novel polynuclear complexes of in situ formed ligands, showing a rich structural diversity. Variable temperature magnetic data have been collected for 1, 2, and 4, and magnetostructural correlations are discussed. Scheme 1. Molecular Structures of H3L1 and in Situ Generated Ligands H2L2−H3L4

■

EXPERIMENTAL SECTION

Materials. All chemicals were of reagent grade quality and were used as received from commercial sources without further purification. Physical Measurements. 1H NMR spectra were recorded on a Bruker AVANCE spectrometer (500 MHz). Elemental analyses were carried out with an Elmentar Vario EL-III analyzer. FT-IR spectra were recorded in the region of 400−4000 cm−1 on a Thermo Electron Avatar 380 FT-IR instrument (KBr Discs). Variable temperature magnetic susceptibility data were collected with a Quantum Design MPMS7 SQUID magnetometer between 2 and 300 K. The data were corrected for the diamagnetism of the sample holder and for diamagnetic contributions with Pascal’s constants; a value of 60 × 10−6 cm3 mol−1 was used for the TIP of the Cu(II) ion. Synthesis. H3L1. A solution of 3-aminopropane-1,2-diol (9.11 g, 0.1 mol) and salicylaldehyde (12.21 g, 0.1 mol) in methanol (100 mL) was stirred for 2 h, then 10.8 g KBH4 was 2090



Article

Table 1. Crystallographic Data and Structure Refinements Summary for Complexes 1−4 empirical formula formula weight space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z Dcalcd (Mg/m3) crystal dimensions (mm3) θ range (deg) unique reflections reflns observed (I > 2σ(I)) GOF final R1a [I > 2σ(I)] R2b (all data) a

1

2

3

4

C20H26Cu2N2O6 517.51 P2(1)/n 10.1612(2) 7.47780(10) 13.2585(3) 90 90.426(2) 90 1007.40(3) 2 1.706 0.38 × 0.32 × 0.30 6.68−59.98 4138 1393 1.007 0.0239 0.0564

C48H67Cu4N4O15 1194.22 C2/c 23.0126(9) 10.0692(3) 22.7967(8) 90 112.358(4) 90 4885.3(3) 4 1.624 0.30 × 0.30 × 0.30 2.71−24.99 22214 2994 0.939 0.0302 0.0843

C80.35H96.35N6.35Na2O21S2.65Zn5 1945.01 C2/c 20.148(2) 15.2270(16) 57.720(5) 90 98.443(1) 90 17516(3) 8 1.475 0.17 × 0.15 × 0.07 2.30−25.02 44463 5263 1.023 0.1159 0. 2582

C38H38N2Ni2O10 800.12 P1̅ 11.4400(11) 12.1709(13) 13.8131(15) 85.546(2) 79.749(1) 65.731(1) 1725.3(3) 2 1.540 0.21 × 0.17 × 0.10 2.36−25.02 9104 3966 1.029 0.0643 0.1674

R = Σ||Fo| − |Fc||/Σ|Fo|. bR2 =Σ||Fo| − |Fc||w1/2/Σ|Fo|w1/2.

constrained to the ideal positions in the refinement procedure. All calculations were performed using SHELX-97 software package.15 Crystal data and experimental details for the crystals are summarized in Table 1, and selected bond lengths and bond angles are given in Supporting Information Table S1.

■

RESULTS AND DISCUSSION Synthesis and Characterization. H3L1 was synthesized as a white solid in a moderate yield by the reaction of 3-aminopropane-1,2-diol with equimolar salicylaldehyde in MeOH followed by reduction of the resulting Schiff base with KBH4. It was reacted with Cu(NO3)2·3H2O in the presence of NaOH as a base to afford a binuclear complex [Cu(HL1)]2 (1). The molecule of H3L1 contains both aminoethanol and aminopropanol units. Thus, H3L1 was reacted with metal salts in the presence of various aldehydes to afford complexes [CuL2]4·4CH3OH (2), [Zn5Na2(L3)4(DMSO)2.65(DMF)1.35]·DMF (3), and [Ni(HL4)]2 (4). In 2 and 3, oxazinane moieties are formed in situ to afford (L2)2−, and (L3)3−, respectively. In contrast, an oxazolidine ring is formed in complex 4 to afford (HL4)2−. For this reaction, a dialdehyde was employed and an H3L1:dialdehyde molar ratio of 2:1 was applied with the purpose of obtaining the metal complex in which both aldehyde groups have been converted into saturated heterocyles. Unexpectedly, in complex 4, (HL4)2− was formed in situ with only one of the aldehyde groups converted and the other one left intact. In summary, facile syntheses of complexes 2−4 were realized with the multidentate ligands formed in situ, which avoids tedious reactions and purification for syntheses of the ligands. Single crystals of 1 and 2 were obtained from slow evaporation of the MeOH solutions, and crystals of 3 and 4 were obtained under solvothermal conditions in mixed solvents of DMF, DMSO, and H2O. To elucidate the structures of these complexes, they were characterized by single-crystal X-ray diffraction analyses. Crystal Structure of [Cu(HL1)]2 (1). Crystal structure of 1 consists of a discrete [Cu(HL1)]2 dimer (Figure 1). Each (HL1)2− ligand coordinates in a tridentate mode (Scheme 2a), with the phenol and one of the alkoxyl groups deprotonated.

Figure 1. View of complex 1. Hydrogen atoms attached to carbons are omitted for clarity. Symmetry operations, A: −x + 1, −y, −z + 1.

The latter O atom bridges two Cu(II) centers, affording a planar Cu2O2 center. The remaining neutral alkoxyl group is left noncoordinated. Thus, each Cu(II) atom is coordinated to one phenoxo O, one amino N, and two bridging alkoxo O atoms, affording a square planar coordination geometry, with coordination bond lengths varying in a range of 1.873(2) ∼ 1.982(2) Å, and the Cu1−O2−Cu1A bridging angle of 99.45(7)°. Strong intramolecular hydrogen bonds occur between the noncoordinated alkoxyl OH and the phenoxo O atoms, with H3···O1A and O3···O1A distances of 1.84, and 2.659(2)Å, respectively. The O3−H3···O1A angle has a large value of 176°, indicating a nearly linear arrangement of O3, H3, and O1A. Along the c-axis, the binuclear units are connected by intermolecular hydrogen bonds between aromatic hydrogens and noncoordinated alkoxyl O atoms from neighboring molecules, with H···O and C···O distances of 2.52 and 3.438(5) Å, respectively, and the C−H···O angle of 169°, thus affording a 1D double-chain supramolecular structure (figure 2). Crystal Structure of [CuL2]4·4CH3OH (2). The crystal structure of 2 consists of a discrete centrosymmetric [CuL2]4 tetramer (Figure 3 and Supporting Information Table S1), and four lattice methanol molecules. In the tetramer, the aminopropanol unit of H3L1 has been reacted with formaldehyde to afford an oxazinane ring, and the resulting H2L2 ligand coordinates in a dianionic form of (L2)2−, with the alkoxyl 2091



Article

Scheme 2. Coordination Modes of the Ligands in Complexes 1−4: (a) (HL1)2− in 1, (b) (L2)2− in 2, (c) (L3)3− in 3, and (d) (HL4)2− in 4a

a

The in situ generated multidentate ligands are shown in blue color except that the oxazinane and oxazolidine rings are shown in red color.

According to this notation, the binding modes of (L2)2‑ in complex 2 can be designated as 3.1121221311 and 3.1131231111, wherein, the numerated metal centers bound by each coordinating atom are denoted in the corresponding subscript. Regarding the bridging geometry, Cu(II)−O−Cu(II) angles lie in the range of 91.02(3)−103.75(3)°, with Cu1···Cu2, Cu1···Cu2A, and Cu2···Cu2A separations of 3.075(1), 3.104(1), and 3.326(1) Å, respectively. Crystal Structure of [Zn5Na2(L3)4(DMSO)2.65(DMF)1.35] ·DMF (3). Complex 3 has an interesting heptanuclear Zn5Na2 core structure (Figure 4). In this complex, the aminopropanol unit of H3L1 has been reacted with salicylaldehyde to afford an

Figure 2. One-dimensional structure of 1 formed by intermolecular hydrogen bonds. H atoms attached to carbons are omitted for clarity.

Figure 3. View of complex 2. Lattice solvents and hydrogen atoms attached to carbons are omitted for clarity. Symmetry operations, A: − x + 2, −y + 1, −z.

and phenol groups deprotonated. The six-membered oxazinane rings adopt chair conformations in the complex. Cu1 coordinates with one amino, one terminal phenoxo, one bridging phenoxo, and two bridging alkoxo groups, in addition to a weakly coordinated cyclic ether O atom, with the Cu1−O3 distance of 2.897(1) Å. Thus, the final coordination environment of Cu1 may be described as “5 + 1”. Cu2 has a coordination environment similar to that of Cu1 except that the bridging moiety involves one phenoxo, and three alkoxo groups, and weak coordination of the ether O atom is associated with a Cu1−O3 distance of 2.893(1) Å. Thus, four copper atoms are bridged by the phenoxo and alkoxo groups, resulting in a relatively rare Cu4O6 face-sharing double defective cubane core.16 The most commonly observed core structure for tetranuclear Cu(II) complexes is a cubane with tetrahedrally arranged Cu(II) centers.14b,c,17−19 Considering the bridging modes, four (L2)2− ligands can be divided into two classes. One utilizes each of the alkoxo and phenoxo group to bridge two metal centers, and the other utilize only the alkoxo group to bridge three metal centers. For presentation of the bridging modes of multidentate ligands, the commonly used notation approach based on Greek letters μ and η, is rather cumbersome. Recently, Harris at Edinburgh20 suggested an alternative notation, i.e., the binding mode is referred to as [X.Y1Y2Y3...Yn], where X is the overall number of metals bound by the whole ligand, and each value of Y refers to the number of metal atoms attached to the different donor atoms. The ordering of Y is listed by the Cahn−Ingold−Prelog priority rules, hence here S is placed before O, and O before N.

Figure 4. View of complex 3 (a) and the Zn5Na2 core structure (b). Disordered DMSO and DMF molecules, and hydrogen atoms are omitted for clarity.

oxazinane ring, and resulting H3L3 ligand coordinates in a trianionic form of (L3)3−, with one alkoxyl and two phenol groups deprotonated. The six-membered oxazinane rings adopt chair conformations in the complex. A central zinc atom Zn1 is coordinated with four O atoms from the alkoxo groups of four (L3)3− ligands. Each of the alkoxo O atom further bridges another Zn(II) atom, resulting in a Zn5 moiety, which is then connected to two Na atoms by two quadruple μ2-phenoxo bridges, finally affording the heteroheptanuclear Zn5Na2 core. The coordination geometry for Zn1 is tetrahedral, with Zn−O bond lengths varying in the range of 1.951−1.977 Å. Zn2, Zn3, Zn4, and Zn5 atoms have similar “5 + 1” coordination geometries. The Zn−O distances for phenoxo and alkoxo groups lie in the range of 1.943−2.181 Å, whereas, the corresponding values for the cyclic ethers vary between 2.610 2092



Article

It is noteworthy that intermolecular C−H···π stacking interactions between the phenyl rings from neighboring molecules are observed. The closest centroid···centroid and H···centroid distances are 5.022(4) Å and 2.84 Å, respectively, and the interplane angle is 82.8(9)°. Furthermore, intermolecular hydrogen bonds occur between the benzyl CH and the phenoxo O atoms, with H···O and C···O distances of 2.47 Å, and 3.437(3) Å, respectively, and the C−H···O angle of 174°. By the linkage of these C−H···π stacking and hydrogen bonding interactions, a 1D linear chain is formed. Interestingly, interchain π···π stacking interactions are observed between the parallel phenyl rings with the closest interplane C···C and centroid···centroid distances of 3.553(2), and 5.391(3) Å, respectively. These values lie above the optimal distances,22 indicating that these interactions are rather weak. Finally, a twodimensional supramolecular network is formed by these interactions (Figure 6).

and 2.710 Å. Each Na(I) atom is coordinated with four bridging phenoxo O atoms and two O atoms from DMSO and DMF. Both Na1 and Na2 have severely distorted octahedral coordination geometries, with Na−O bond distances varying in the ranges of 2.21−3.065 and 2.31−2.760 Å, respectively. Regarding the binding modes of (L3)3−, each ligand bridges three Zn atoms and one Na atom. Take the upper left ligand for example, the alkoxo O2 atom (Figure 4a) bridges Zn1 and Zn2, the phenoxo O3 atom bridges Zn2, Zn3, and Na2, and the phenoxo O4 atom bridges Zn2 and Na2. Thus, according to the Harris notation, the bridging mode of (L3)3− in complex 3 can be designated as 4.21221311312411, wherein, the numerated metal centers bound by each coordinating atom are denoted in the corresponding subscript. The occurrence of heterometallic structure involving the coordination of Na(I) may be related to the existence of multiple negatively charged phenoxo O atoms, which have good affinity for Na(I) and the distances between these phenoxo groups are too large for further binding of another Zn(II), but suitable for Na(I), which has a larger radius Similarly, an interesting example of heterometallic complex was recently reported involving a Ni4Na3 core with multiple bridging O atoms from PyCH2O− ligands.21 Crystal Structure of [Ni(HL4)]2 (4). The crystal of 4 consists of two crystallographically independent, and chemically similar, binuclear Ni(II) coordination moieties, with one of them shown in Figure 5. In contrast to the oxazinane rings observed in complexes 2 and 3, the aminoethanol unit of H3L1

Figure 6. Two-dimensional supramolecular network of 4 formed by intermolecular π···π, C−H···π, and C−H···O interactions. Nonhydrogen bonded H atoms are omitted for clarity.

Magnetic Studies. Magneto-structural correlations are important in understanding the magnetic couplings between metal centers mediated by various bridges and in designing novel molecular magnetic materials. In the crystal structures of complexes 1, 2, and 4, the paramagnetic Cu(II) and Ni(II) centers are bridged by O atoms from alkoxo and phenoxo groups. To understand the magnetic interactions mediated by the bridges in these complexes, variable temperature magnetic susceptibilities were measured in a temperature range of 2−300 K. The data were analyzed and fitted based on the structures to obtain the coupling constants, and magneto-structural correlations have been performed. For complex 1, the χmT product at 290 K is 0.475 cm3·K·mol−1. Gradual decrease of this product is observed as the temperature is decreased (Figure 7), which is indicative of an intramolecular antiferromagnetic interaction between the Cu(II) centers. The data were fitted to the Bleaney−Bowers equation (eq 1):23

Figure 5. View of one of the binuclear moieties in the crystal of complex 4. Hydrogen atoms are omitted for clarity. Symmetry operations, A: −x + 1, −y + 1, −z + 1.

has been reacted with one of the aldehyde groups in the dialdehyde to afford a five-membered oxazolidine ring, and resulting H3L4 ligand coordinates in a dianionic form of (HL4)2−, with two phenol groups deprotonated and the alkoxyl group left neutral. The five-membered oxazolidine rings adopt envelope conformations in the complex. In the centrosymmetric binuclear structure, two Ni(II) atoms have the same coordination environments. Ni1 is coordinated with two bridging phenoxo O2 and O2A atoms, one terminal phenoxo O3 atom, alkoxo O5, amino N1, in addition to O1 from the remaining aldehyde group. Ni(II) centers are bridged by two phenoxo O atoms, with Ni1−O2 and Ni1−O2A distances of 2.046(3) and 2.018(3) Å, respectively, and Ni1−O2−Ni1A angles of 96.00(14)°. Interestingly, two strong intramolecular hydrogen bonds are observed between the coordinated alkoxyl groups and phenoxo groups, with the H···O distances of 1.87 Å, and the O−H···O angles of 162°.

χmT = (1 − ρ) ·

2Ng 2μ2B k

·

1 3 + e−2J / kT

+ ρ·

N β2g 2 2k (1)

Equation 1 was derived from the isotropic Hamiltonian model with H = −2JS1S2, and all symbols have their usual meanings. 2093



Article

Scheme 3. Magnetic Exchange Pathways for 2

structural data. For octahedral Cu(II) complexes, an unpaired electron occupies the dx2−y2 orbital, which is associated with shorter coordination bonds in the equatorial plane as compared with those at the axial positions due to Jahn−Teller effect. Thus, the magnetic orbitals for Cu2 and Cu2A are parallel, indicating that J1 may be antiferromagnetic in nature. The magnetic orbitals for the Cu(II) centers associated with J2 and J3 are nearly perpendicular, indicative of ferromagnetic interactions. Thus, the magnetic data were fitted to the 3 − J model. Unfortunately, no reasonable result could be obtained. Then we continued to try a 2 − J model, assuming that J2 = J3, based on their similar bridging parameters. Again, no reasonable result could be obtained. For complex 4, the χmT product at 300 K is 2.52 cm3·K·mol−1. Gradual decrease of this product is observed as the temperature is decreased (Figure 9), which is indicative of

Figure 7. Plot of products χmT versus temperature for complex 1; the solid line represents the best calculated fit (see text for the fitted parameters).

The best fit gave ρ = 0.0097(8), g = 2.080(7), 2J = −278(2) cm−1, and R = 1 × 10−5. Cu−O−Cu bridging angle (θ) has been found to be a crucial geometrical parameter for the magnetic coupling (J) between the Cu(II) centers equatorially bridged by a pair of hydroxides, phenoxides or alkoxides. Ferromagnetism is associated with smaller angles, and antiferromagnetism with larger ones, and linear correlations between θ and J have been proposed.24 The best fit −2J value of 278 cm−1 for complex 1 associated with a Cu−O−Cu bridging angle of 99.45(7)° is comparable to the value of 308 cm−1 expected from a empirical linear relationship (−2J = 82.1θ − 7857 cm−1) proposed for binuclear Cu(II) complexes with the metal centers equatorially bridged by a pair of alkoxides.24d For complex 2, the χmT product at 300 K is 1.69 cm3·K·mol−1. Gradual decrease of this product is observed as the temperature is decreased (Figure 8), which is also indicative

Figure 9. Plot of products χmT vs temperature for complex 4; the solid line represents the best calculated fit (see text for the fitted parameters).

an intramolecular antiferromagnetic interaction between the Ni(II) centers. The data were fitted according to a typical binuclear model. The best fit gave J = −4.68 cm−1, g = 2.26, R = 8.3 × 10−5, indicative of a weak antiferromagnetic coupling. Nag and co-workers reported a linear relationship between the exchange (J) and the Ni−O−Ni bridging angle (θ) for bis(μ2phenoxo)dinickel(II) complexes, J = −7.27θ + 704.06 cm−1.26 According to this relationship, a J value of 6.14 cm−1 is anticipated for complex 4 based on a θ value of 96.00°. Compared to this expected value, the obtained J value of −4.68 cm−1 shows a more antiferromagnetic trend, which may be related to the structural difference between complex 4 and the complexes utilized for the magneto-structural correlations. Meanwhile, the more antiferromagnetic coupling may also

Figure 8. Plot of products χmT vs temperature for complex 2.

of a net intramolecular antiferromagnetic interaction between the Cu(II) centers. Considering the structural symmetry, the data could be fitted according to a 3-J model (Scheme 3). As mentioned above, the Cu−O−Cu bridging angle has been found to be a crucial geometrical parameter for the magnetic coupling between the Cu(II) centers. In addition, the arrangement of the magnetic orbitals is essential for governing the nature to be ferro- or antiferromagnetic. Generally, antiferromagnetism is associated with parallel magnetic orbitals, and ferromagnetism with perpendicular ones.14c,25 For complex 2, the magnetic orbitals can be readily obtained from the 2094



Article

(e) Striegler, S.; Dittel, M. J. Am. Chem. Soc. 2003, 125, 11518. (f) Henkel, G.; Krebs, B. Chem. Rev. 2004, 104, 801. (2) (a) Yoo, J.; Yamaguchi, A.; Nakano, M.; Krzystek, J.; Streib, W. E.; Brunel, L. C.; Ishimoto, H.; Christou, G.; Hendrickson, D. N. Inorg. Chem. 2001, 40, 4604. (b) Soler, M.; Wernsdorfer, W.; Folting, K.; Pink, M.; Christou, G. J. Am. Chem. Soc. 2004, 126, 2156. (c) Ako, A. M.; Hewitt, I. J.; Mereacre, V.; Clérac, R.; Wernsdorfer, W.; Anson, C. E.; Powell, A. K. Angew. Chem., Int. Ed. 2006, 45, 4926. (d) Bagai, R.; Christou, G. Chem. Soc. Rev. 2009, 38, 1011. (e) Ako, A. M.; Mereacre, V.; Lan, Y. H.; Anson, C. E.; Powell, A. K. Chem.Eur. J. 2011, 17, 4366. (3) (a) Rajaraman, G.; Murugesu, M.; Sanudo, E. C.; Soler, M.; Wernsdorfer, W.; Helliwell, M.; Muryn, C.; Raftery, J.; Teat, S. J.; Christou, G.; Brechin, E. K. J. Am. Chem. Soc. 2004, 126, 15445. (b) Stamatatos, T. C.; Foguet-Albiol, D.; Lee, S. C.; Stoumpos, C. C.; Raptopoulou, C. P.; Terzis, A.; Wernsdorfer, W.; Hill, S. O.; Perlepes, S. P.; Christou, G. J. Am. Chem. Soc. 2007, 129, 9484. (c) Ibrahim, M.; Lan, Y. H.; Bassil, B. S.; Xiang, Y. X.; Suchopar, A.; Powell, A. K.; Kortz, U. Angew. Chem., Int. Ed. 2011, 50, 4708. (d) Zhang, S. Y.; Shi, W.; Lan, Y. H.; Xu, N.; Zhao, X. Q.; Powell, A. K.; Zhao, B.; Cheng, P.; Liao, D. Z.; Yan, S. P. Chem. Commun. 2011, 47, 2859. (e) Zhu, Y. Y.; Guo, X.; Cui, C.; Wang, B. W.; Wang, Z. M.; Gao, S. Chem. Commun. 2011, 47, 8049. (4) (a) Tanase, T.; Tamakoshi, S.; Doi, M.; Mikuriya, M.; Sakurai, H.; Yano, S. Inorg. Chem. 2000, 39, 692. (b) Tanase, T.; Inukai, H.; Onaka, T.; Kato, M.; Yano, S.; Lippard, S. J. Inorg. Chem. 2001, 40, 3943. (c) Moragues-Canovas, M.; Helliwell, M.; Ricard, L.; Riviere, E.; Wernsdorfer, W.; Brechin, E.; Mallah, T. Eur. J. Inorg. Chem. 2004, 2219. (d) Li, B.; Yang, F.; Li, G.; Liu, D.; Zhou, Q.; Shi, Z.; Feng, S. Cryst. Growth Des. 2011, 11, 1475. (e) Jiang, J. C.; Chu, Z. L.; Huang, W.; Wang, G.; You, X. Z. Inorg. Chem. 2010, 49, 5897. (f) Das, A.; Gieb, K.; Krupskaya, Y.; Demeshko, S.; Dechert, S.; Klingeler, R. d.; Kataev, V.; Büchner, B.; Müller, P.; Meyer, F. J. Am. Chem. Soc. 2011, 133, 3433. (5) (a) Wittick, L. M.; Murray, K. S.; Moubaraki, B.; Batten, S. R.; Spiccia, L.; Berry, K. J. Dalton. Trans. 2004, 1003. (b) Striegler, S.; Dunaway, N. A.; Gichinga, M. G.; Barnett, J. D.; Nelson, A. G. D. Inorg. Chem. 2010, 49, 2639. (c) Striegler, S.; Dittel, M.; Kanso, R.; Alonso, N. A.; Duin, E. C. Inorg. Chem. 2011, 50, 8869. (d) Guo, Y. N.; Xu, G. F.; Gamez, P.; Zhao, L.; Lin, S. Y.; Deng, R.; Tang, J.; Zhang, H. J. J. Am. Chem. Soc. 2010, 132, 8538. (6) (a) Tong, M. L.; Chen, X. M.; Ye, B. H.; Ji, L. N. Angew. Chem., Int. Ed. 1999, 38, 2237. (b) Brooker, S. Coord. Chem. Rev. 2001, 222, 33. (c) Sylvestre, I.; Wolowska, J.; Kilner, C. A.; McInnes, E. J. L.; Halcrow, M. A. Dalton. Trans. 2005, 3241. (d) Milios, C. J.; Inglis, R.; Vinslava, A.; Bagai, R.; Wernsdorfer, W.; Parsons, S.; Perlepes, S. P.; Christou, G.; Brechin, E. K. J. Am. Chem. Soc. 2007, 129, 12505. (e) Wang, H.; Zhang, L. F.; Ni, Z. H.; Zhong, W. F.; Tian, L. J.; Jiang, J. Cryst. Growth Des. 2010, 10, 4231. (f) Majumder, S.; Sarkar, S.; Sasmal, S.; Sañudo, E. C.; Mohanta, S. Inorg. Chem. 2011, 50, 7540. (7) (a) Zhang, L. Y.; Liu, G. F.; Zheng, S. L.; Ye, B. H.; Zhang, X. M.; Chen, X. M. Eur. J. Inorg. Chem. 2003, 2965. (b) Li, X. J.; Wang, X. Y.; Gao, S.; Cao, R. Inorg. Chem. 2006, 45, 1508. (c) Qu, L. L.; Zhu, Y. L.; Li, Y. Z.; Du, H. B.; You, X. Z. Cryst. Growth Des. 2011, 11, 2444. (d) Chen, S. S.; Bai, Z. S.; Fan, J.; Lv, G. C.; Su, Z.; Chen, M. S.; Sun, W. Y. CrystEngComm 2010, 12, 3091. (8) (a) Jia, W. L.; Wang, R. Y.; Song, D. T.; Ball, S. J.; McLean, A. B.; Wang, S. N. Chem.Eur. J. 2005, 11, 832. (b) Martin, D. P.; Montney, M. R.; Supkowski, R. M.; LaDuca, R. L. Cryst. Growth Des. 2008, 8, 3091. (c) Sumby, C. J. Coord. Chem. Rev. 2011, 255, 1937. (d) Li, N.; Jiang, F. L.; Chen, L. A.; Li, X. J.; Chen, Q. H.; Hong, M. C. Chem. Commun. 2011, 47, 2327. (e) Yang, J.; Wu, B.; Zhuge, F.; Liang, J.; Jia, C.; Wang, Y. Y.; Tang, N.; Yang, X. J.; Shi, Q. Z. Cryst. Growth Des. 2010, 10, 2331. (9) (a) Song, R. F.; Xie, Y. B.; Li, J. R.; Bu, X. H. CrystEngComm 2005, 7, 249. (b) Dobrzynska, D.; Duczmal, M.; Jerzykiewicz, L. B.; Warchulska, J.; Drabent, K. Eur. J. Inorg. Chem. 2004, 110. (c) Hashimoto, A.; Yamaguchi, H.; Suzuki, T.; Kashiwabara, K.; Kojima, M.; Takagi, H. D. Eur. J. Inorg. Chem. 2010, 39. (d) Suzuki, T.;

suggest the presence of alternative antiferromagnetic superexchange pathways in addition to the phenoxo bridges. As mentioned above, intramolecular hydrogen bonds between the coordinated phenoxo and alkoxyl groups are observed in the molecule of 4. And hydrogen bonds have been reported to propagate antiferromagnetic interactions between metal centers in a variety of transition metal complexes.27 Hence, the antiferromagnetic coupling in complex 1 may be partly ascribed to the superexchange through the intramolecular hydrogen bonds.

■

CONCLUSIONS Complexes of ligands containing oxazinane and oxazolidine rings are rather rare. In this work, we synthesized a novel ligand H3L1, which was utilized to synthesize a dialkoxo-bridged binuclear Cu(II) complex, [Cu(HL1)]2 (1). Considering the fact that H3L1 contains both aminoethanol and aminopropanol units in the molecule, it was further reacted with metal salts in the presence of various aldehydes to afford [CuL2]4·4CH3OH (2) [Zn5Na2(L3)4(DMSO)2.65(DMF)1.35]·DMF (3), and [Ni(HL4)]2 (4). These complexes are tetranuclear, heteroheptanuclear, and binuclear, respectively. In these complexes, oxazinane and oxazolidine rings are formed in situ from the reaction of corresponding aldehydes with the aminoethanol and aminopropanol units, respectively. These results indicate that the combination of in situ formed oxazinane and oxazolidine rings with appended phenol and alkoxyl functionalities is an efficient approach to developing novel ligands and complexes with a rich structural diversity. Facile syntheses of the complexes were realized with the in situ formed ligands, which avoids tedious syntheses of the multidentate ligands. Variable-temperature magnetic data were collected for complexes 1, 2, and 4, and magneto-structural correlations were discussed.

■

ASSOCIATED CONTENT

S Supporting Information *

Crystallographic information files (CIF format) for complexes 1−4 and tables for bond lengths and angles. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] (Y.X.). Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by NSFC/China, the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, Program for New Century Excellent Talents in University (NCET), Innovation Program of Shanghai Municipal Education Commission, the Fundamental Research Funds for the Central Universities (WK1013002), and SRFDP (20100074110015).

■

REFERENCES

(1) (a) Solomon, E. I.; Lowery, M. D. Science 1993, 259, 1575. (b) Sellmann, D. Angew. Chem., Int. Ed. 1993, 32, 64. (c) Ferreira, K. N.; Iverson, T. M.; Maghlaoui, K.; Barber, J.; Iwata, S. Science 2004, 303, 1831. (d) Spencer, J.; Read, J.; Sessions, R. B.; Howell, S.; Blackburn, G. M.; Gamblin, S. J. J. Am. Chem. Soc. 2005, 127, 14439. 2095



Article

Chem. Soc., Dalton Trans. 1980, 875. (e) Venegas-Yazigi, D.; Aravena, D.; Spodine, E.; Ruiz, E.; Alvarez, S. Coord. Chem. Rev. 2010, 254, 2086. (25) (a) Mukherjee, A.; Raghunathan, R.; Saha, M. K.; Nethaji, M.; Ramasesha, S.; Chakravarty, A. R. Chem.Eur. J. 2005, 11, 3087. (b) Tan, X. S.; Nukada, R.; Mikuriya, M.; Nakano, Y. J. Chem. Soc., Dalton Trans. 1999, 2415. (26) Nanda, K. K.; Das, R.; Thompson, L. K.; Bridson, J. N.; Nag, K. J. Chem. Soc., Chem. Commun. 1994, 1337. (27) (a) Costa, J. S.; Bandeira, N. A. G.; Le Guennic, B.; Robert, V.; Gamez, P.; Chastanet, G.; Ortiz-Frade, L.; Gasque, L. Inorg. Chem. 2011, 50, 5696. (b) Przychodzen, P.; Rams, M.; Guyard-Duhayon, C.; Sieklucka, B. Inorg. Chem. Commun. 2005, 8, 350. (c) Barea, E.; Navarro, J.A. R.; Salas, J. M.; Masclocchi, N.; Galli, S.; Sironi, A. Inorg. Chem. 2004, 43, 473. (d) Xie, Y. S.; Liu, Q. L.; Jiang, H.; Du, C. X.; Xu, X. L.; Yu, M. G.; Zhu, Y. New J. Chem. 2002, 26, 176.

Yamaguchi, H.; Hashimoto, A.; Nozaki, K.; Doi, M.; Inazumi, N.; Ikeda, N.; Kawata, S.; Kojima, M.; Takagi, H. D. Inorg. Chem. 2011, 50, 3981. (e) Wang, H. M.; Liu, Z. L.; Liu, C. M.; Zhang, D. Q.; Lu, Z. L.; Geng, H.; Shuai, Z. G.; Zhu, D. B. Inorg. Chem. 2004, 43, 4091. (10) (a) D’hooghe, M.; Dekeukeleire, S.; Mollet, K.; Lategan, C.; Smith, P. J.; Chibale, K.; De Kimpe, N. J. Med. Chem. 2009, 52, 4058. (b) Gras, J.; Taulier, E. Synthesis 2006, 1093. (c) He, P.; Zhu, S. Z. Tetrahedron 2005, 61, 6088. (d) M.DePorter, S.; Jacobsen, A. C.; Partridge, K. M.; Williamson, K. S.; Yoon, T. P. Tetrahedron Lett. 2010, 51, 5223. (11) (a) Ito, A.; Nakano, Y.; Urabe, M.; Tanaka, K.; Shiro, M. Eur. J. Inorg. Chem. 2006, 3359. (b) Caputo, C. A.; Jones, N. D. Dalton Trans. 2007, 4627. (12) Banerjee, A.; Ganguly, S.; Chattopadhyay, T.; Banu, K. S.; Patra, A.; Bhattacharya, S.; Zangrando, E.; Das, D. Inorg. Chem. 2009, 48, 8695. (13) (a) Fang, Z. L.; He, J. G.; Zhang, Q. S.; Zhang, Q. K.; Wu, X. Y.; Yu, R. M.; Lu, C. Z. Inorg. Chem. 2011, 50, 11403. (b) Lobana, T. S.; Sultana, R.; Hundal, G.; Butcher, R. J. Dalton Trans. 2010, 39, 7870. (c) Liu, D.; Huang, G.; Huang, C.; Huang, X.; Chen, J.; You, X. Cryst. Growth Des. 2009, 9, 5117. (d) Hao, Z. M.; Zhang, X. M. Cryst. Growth Des. 2007, 7, 64. (e) Barman, S.; Furukawa, H.; Blacque, O.; Venkatesan, K.; Yaghi, O. M.; Jin, G.-X.; Berke, H. Chem Commun 2011, 47, 11882. (14) (a) Xie, Y. S.; Liu, Q. L.; Jiang, H.; Ni, J. Eur. J. Inorg. Chem. 2003, 4010. (b) Xie, Y. S.; Bu, W. M.; Xu, X. L.; Jiang, H.; Liu, Q. L.; Xue, Y.; Fan, Y. G.. Inorg. Chem. Commun. 2001, 4, 558. (c) Xie, Y. S.; Ni, J.; Zheng, F. K.; Cui, Y.; Wang, Q. G.; Ng, S. W.; Zhu, W. H. Cryst. Growth Des. 2009, 9, 118. (d) Wei, K. J.; Xie, Y. S.; Ni, J.; Zhang, M.; Liu, Q. L. Cryst. Growth Des. 2006, 6, 1341. (15) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112. (16) (a) Tangoulis, V.; Raptopoulou, C. P.; Paschalidou, S.; Tsohos, A. E.; Ba kalbassis, E. G.; Terzis, A.; Perlepes, S. P. Inorg. Chem. 1997, 36, 5270. (b) Koikawa, M.; Yamashita, H.; Tokii, T. Inorg. Chim. Acta 2004, 357, 2635. (c) Morishita, Y.; Kogane, T.; Nogami, T.; Ishida, T. Dalton Trans. 2006, 4438. (d) He, M. H.; Zhang, W.; Yu, Z. W. Inorg. Chim. Acta 2010, 363, 3619. (e) Mobin, S. M.; Srivastava, A. K.; Mathur, P.; Lahiri, G. K. Dalton Trans. 2010, 39, 1447. (17) (a) Mertz, L.; Haase, W. J. Chem. Soc., Dalton Trans. 1978, 1594. (b) Schwabe, L.; Haase, W. J. Chem. Soc., Dalton Trans. 1985, 1909. (18) (a) Sletten, J.; Sørensen, A.; Julve, M.; Journaux, Y. Inorg. Chem. 1990, 29, 5054. (b) Real, J. A.; De Munno, G.; Chiappetta, R.; Julve, M.; Lloret, F.; Journaux, Y.; Colin, J. C.; Blondin, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 1184. (c) Oshio, H.; Saito, Y.; Ito, T. Angew. Chem., Int. Ed. Engl. 1997, 36, 2673. (19) (a) Gottschaldt, M.; Görls, H.; Jäger, E. G.; Klemm, D. Chem. Eur. J. 2001, 7, 2143. (b) Lopez, N.; Vos, T. E.; Arif, A. M.; Shum, W. W.; Noveron, J. C.; Miller, J. S. Inorg. Chem. 2006, 45, 4325. (c) Aronica, C.; Chumakov, Y.; Jeanneau, E.; Luneau, D.; Neugebauer, P.; Barra, A. L.; Gillon, B.; Goujon, A.; Cousson, A.; Tercero, J.; Ruiz, E. Chem.Eur. J. 2008, 14, 9540. (d) Thakurta, S.; Roy, P.; Butcher, R. J.; Fallah, M. S. E.; Tercero, J.; Garribba, E.; Mitra, S. Eur. J. Inorg. Chem. 2009, 4385. (20) Coxall, R. A.; Harris, S. G.; Henderson, D. K.; Parsons, S.; Tasker, P. A.; Winpenny, R. E. P. J. Chem. Soc., Dalton Trans. 2000, 2349. (21) Zhang, J.; Teo, P.; Pattacini, R.; Kermagoret, A.; Welter, R.; Rogez, G.; Hor, T. S. A.; Braunstein, P. Angew. Chem., Int. Ed. 2010, 49, 4443. (22) (a) Tsuzuki, S.; Honda, K.; Uchimaru, T.; Mikami, M.; Tanabe, K. J. Am. Chem. Soc. 2002, 124, 104. (b) Kamishima, M.; Kojima, M.; Yoshikawa, Y. J. Comput. Chem. 2001, 22, 835. (c) Janiak, C. J. Chem. Soc., Dalton Trans. 2000, 3885. (23) Bleaney, B.; Bowers, K. D. Proc. R. Soc. London 1952, A214, 451. (24) (a) Crawford, V. H.; Richardson, H. W.; Wasson, J. R.; Hodgson, D. J.; Hatfield, W. E. Inorg. Chem. 1976, 15, 2107. (b) Ruiz, E.; Alemany, P.; Alvarez, S.; Cano, J. Inorg. Chem. 1997, 36, 3683. (c) Thompson, L. K.; Mandal, S. K.; Tandon, S. S.; Bridson, J. N.; Park, M. K. Inorg. Chem. 1996, 35, 3117. (d) Merz, L.; Haase, W. J. 2096


Polynuclear Complexes of Ligands Containing in Situ Formed

Recommend Documents