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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >VANADIUM(V) COMPLEXES WITH FLEXIBLE AND HYDROLYTICALLY STABLE AMINE ALCOHOL LIGANDS AND THEIR ISOMERIZATION IN SOLUTION - MODELS FOR THE INTERACTION OF VANADIUM(V) WITH BIOGENIC LIGANDS
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VANADIUM(V) COMPLEXES WITH FLEXIBLE AND HYDROLYTICALLY STABLE AMINE ALCOHOL LIGANDS AND THEIR ISOMERIZATION IN SOLUTION - MODELS FOR THE INTERACTION OF VANADIUM(V) WITH BIOGENIC LIGANDS

机译：钒（V）络合物与柔性和水解稳定的氨基醇配体及其在溶液中的异构化-钒（V）与生物原体相互作用的模型

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摘要

The hydrolytically stable trivalent, pentadentate amine alcohol ligands 1,1-bis(2-hydroxyethyl)-4-(2-hydroxy-5-R-benzyl)-1 ,4-diazabutane 2 (H(3)hebab-R; a: R = H, b: R=OMe, c: R=Br, d: R=NO2) react with ammonium metavanadate to form the oxovanadium(V) complexes [VO(hebab-R)] 4, which have been characterized by H-1, C-13, and V-51 NMR, vibrational (IR, Raman, and resonance Raman) and electronic spectroscopy. According the high flexibility of the ligand systems the complexes 4 possess two different possible structures in solution. These two isomers differ in the ligand arrangement: fac-4 possesses a facial configuration of the phenolate oxygen and the two amine nitrogen donors with the oxo group trans to the tertiary amine nitrogen atom, whereas mer-4 is characterized by a meridional configuration of the phenolate oxygen and the two amine nitrogen donors with the oxo group trans to the secondary amine nitrogen atom. The two isomers are related by an isomerization equilibrium proceeding via a rotation about a pseudo C-3 axis of the octahedral coordination environment. This isomerization mechanism seems to be of general importance, since it can also account for the solution structures of oxovanadium(V), cis-dioxovanadium(V) and cis-dioxomolybdenum(VI) complexes of flexible high-denticity ligand systems. The electronic influence of the para substituent at the phenolate on the isomerization reaction has been investigated by V-51 NMR spectrnscopy. The thermodynamic parameters determined from the variable-temperature V-51 NMR data show the fac-isomers to be more stable in all cases. Although the smallest Delta H degrees is observed for the methoxy substituted derivative 4b, the X-ray crystal structure analysis shows that even in this case solely the fac-isomer is present in the solid state. For 4b the H-1 and C-13 NMR data of both isomers can be observed and assigned. The data reveal a pronounced dependence of the coordination induced shift for the relevant resonances on the relative orientation of the chelate rings with respect to the oxo group at the vanadium center, leading to characteristic resonance patterns. Additional information on the electronic structure of the complexes 4 and the analogous Schiff base derivatives [VO(sabhea-R)] 3 (H(3)sabhea-R = N-(5-R-salicylidene)-2-(bis(2-hydroxyethyl)-amino)ethylamine; a: R=H, b: R=OMe, c: R=Br, d: R=NO2) has been derived from cyclic voltammetry and density functional calculations. The methanolysis reaction of the complexes 4 has been studied by V-51 NMR spectroscopy. A penta-coordinate intermediate has been observed, which indicates the semilabile character of the diethanolamine fragment of the ligand systems 2 in the corresponding oxovanadium(V) complexes. [References: 83]
机译：水解稳定的三价五齿胺醇配体1,1-双（2-羟乙基）-4-（2-羟基-5-R-苄基）-1,4-二氮杂丁烷2（H（3）hebab-R; a ：R ＝ H，b：R ＝ OMe，c：R ＝ Br，d：R ＝ NO 2）与偏钒酸铵反应形成氧钒（V）络合物[VO（hebab-R）] 4，其特征在于H-1，C-13和V-51 NMR，振动（IR，拉曼和共振拉曼）和电子光谱。根据配体系统的高柔性，复合物4在溶液中具有两种不同的可能结构。这两个异构体的配体排列不同：fac-4具有酚盐氧的面部构型，两个胺氮供体的氧代基团可转化为叔胺氮原子，而mer-4的特征是其子午线构型。酚氧和带有氧代基团的两个胺氮供体转化为仲胺氮原子。两种异构体通过绕八面体配位环境的伪C-3轴旋转而进行的异构化平衡相关。这种异构化机制似乎具有普遍的重要性，因为它也可以解释柔性高确定性配体系统的氧钒（V），顺二氧钒（V）和顺二氧钼（VI）配合物的溶液结构。通过V-51 NMR光谱研究了在酚盐上的对位取代基对异构化反应的电子影响。由可变温度V-51 NMR数据确定的热力学参数表明，在所有情况下，fac异构体都更稳定。尽管对于甲氧基取代的衍生物4b观察到最小的ΔH度，但是X射线晶体结构分析表明，即使在这种情况下，仅fac-异构体也以固态存在。对于4b，可以观察到并分配两种异构体的H-1和C-13 NMR数据。数据揭示了相关共振的配位诱导位移明显依赖于螯合物环相对于钒中心的氧代基团的相对取向，从而导致特征共振模式。有关络合物4和类似席夫碱衍生物[VO（sabhea-R）] 3（H（3）sabhea-R = N-（5-R-水杨基）-2-（bis（2 -羟乙基）-氨基）乙胺; a：R ＝ H，b：R ＝ OMe，c：R ＝ Br，d：R ＝ NO 2）已经从循环伏安法和密度泛函计算中得出。通过V-51NMR光谱研究了配合物4的甲醇分解反应。已经观察到五配位中间体，其表明在相应的氧钒（V）配合物中配体系统2的二乙醇胺片段的半不稳定特征。 [参考：83]

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