Syntheses, x-ray structures, and solution properties of [V4O4{(OCH2)(3)CCH3}(3)(OC2H5)(3)] and [V4O4{(OCH2)(3)CCH3}(2)(OCH3)(6)]: Examples of new ligand coordination modes
Syntheses, x-ray structures, and solution properties of [V4O4{(OCH2)(3)CCH3}(3)(OC2H5)(3)] and [V4O4{(OCH2)(3)CCH3}(2)(OCH3)(6)]: Examples of new ligand coordination modes
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DOI：
10.1021/ic961037g
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发表时间：
1997-03-12
影响因子：
4.6
通讯作者：
Miller, MM
中科院分区：
文献类型：
--
作者：
Crans, DC;Jiang, FL;Miller, MM
含烷氧基配体的四核钒配合物[V4 O 4 {mu，mu，mu（3）-（OCH 2）（3）CCH 3}（2）（OCH 3）（6）]（1）和[V4 O 4 {mu-（OCH 2）（3）CCH 3}{mu，mu（3）-（OCH 2）（3）CCH 3}（OR）（3）]以VO（OR）（3）和H（3）thme（H（3）thme = 1，1，1-三羟甲基乙烷）为原料，在乙醇中反应，合成了三种三羟甲基乙烷（R = C2 H5（2），R = CH（CH 3）（2）（3），R = CH 3（4））。配合物1属于单斜晶系，空间群P2（1）/n，晶胞参数为：a = 9.646（4）埃，B = 11.502（3）埃，c = 11.960（3）埃，β = 90.20（3）度，V = 1326.9（7）埃，Z = 2，R（wR（2））= 0.045（0.143）。配合物2也属于单斜晶系，空间群P2（1）/n，a = 8.290（8）埃，B = 12.237（2）埃，c = 29.118（4）埃，β = 89.455（9）度，V = 2954（3）埃，Z = 4，R（wR（2））= 0.049（0.126）。1和2都是具有共同[V_4O_（16）]（12-）核的中性离散配合物，其由两个（1）或三个（2）三齿三（3-）配体和六个（1）或三个（2）RO（-）基团螯合的四个钒（V）原子组成。化合物1表现出晶体学上所需的反转中心;相比之下，配合物2没有表现出晶体学上强加的对称性，并且其三个三烷氧基配体各自以不同的方式配位（其中一个三烷氧基（3-）以新的配位模式与氧以末端、双桥连和三桥连模式配位）。化合物1和2在溶液中均保持其结构，尽管化合物1在溶解时也形成第二次要物质。通过V-51和H-1 NMR谱研究了配合物2和3中RO（-）基团的顺序交换。例如，[V_4O_4（thme）（3）（OC_2H_5）（3）]将与CH_3OH反应生成[V_4O_4（thme）（3）（OCH_3）（3）]（4）发现这些反应是可逆的。发现醇交换反应的时间尺度根据正在进行交换的钒中心而变化。
Tetranuclear vanadium complexes with alkoxy ligands, [V4O4{mu,mu,mu(3)-(OCH2)(3)CCH3}(2)(OCH3)(6)] (1) and [V4O4{mu-(OCH2)(3)CCH3}{mu,mu(3)-(OCH2)(3)CCH3}{mu,mu,mu(3)-(OCH2)(3)CCH3}(OR)(3)] (R = C2H5 (2), R = CH(CH3)(2) (3), R = CH3 (4)), were synthesized by reacting VO(OR)(3) and H(3)thme (H(3)thme = 1,1,1-tris(hydroxymethyl)ethane) in alcohol. Complex 1 crystallized in the monoclinic space group P2(1)/n with a = 9.646(4) Angstrom, b = 11.502(3) Angstrom, c = 11.960(3) Angstrom, beta = 90.20(3)degrees, V = 1326.9 (7) Angstrom(3), Z = 2 and R (wR(2)) = 0.045 (0.143). Complex 2 also crystallized in the monoclinic space group P2(1)/n with a = 8.290(8) Angstrom, b = 12.237(2) Angstrom, c = 29.118(4) Angstrom, beta = 89.455(9)degrees, V = 2954(3) Angstrom(3), Z = 4, and R (wR(2)) = 0.049 (0.126). Both 1 and 2 are neutral, discrete complexes possessing a common [V4O16](12-) core, which consists of four vanadium(V) atoms chelated by two (1) or three (2) tridentate thme(3-) ligands and by six (1) or three (2) RO(-) groups. Compound 1 exhibits a crystallographically required inversion center; in contrast, complex 2 exhibits no crystallographically imposed symmetry, and its three trialkoxy ligands each coordinate differently (one thme(3-) is coordinated in a new coordination mode with the oxygens in a terminal, doubly-bridging and triply-bridging mode). Both compounds 1 and 2 maintain their structures in solution, although compound 1 also forms a second minor species upon dissolution. Sequential exchanges of the RO(-) groups in complexes 2 and 3 were investigated by V-51 and H-1 NMR spectroscopy. For example, [V4O4(thme)(3)(OC2H5)(3)] will react with CH3OH to generate [V4O4(thme)(3)(OCH3)(3)] (4) These reactions were found to be reversible. The time scale of the alcohol exchange reactions were found to vary depending on the vanadium center that is undergoing the exchange.