【摘要】 α-Keggin型杂多阴离子(HPA)簇合物[XM12O40]n–(X=Si,P;M=Mo,W)的氧化还原性能主要取决于构成其外围结构的金属氧笼{M12O36},它就如同一个"仓库",电子和质子的转移和跃迁主要发生在该笼上.改变金属氧笼M(如进行钒V取代)以及中心杂原子X的组成,可以实现在原子和分子水平上对α-Keggin型杂多阴离子簇合物的氧化还原性能进行调控的目的.本文结合实验研究,对最近该类杂多阴离子簇合物的金属笼上发生钒取代前后的氧化性能所作的理论研究进行了综述.理论模拟和计算表明,当电负性较小的V取代Keggin金属氧笼上的M后,所形成物种的氧化能力得到了不同程度的增强.首次建立了钒取代的α-Keggin型HPA[PMo12–nVnO40](n+3)–(n=1~3)的微观结构与其基于单个钒的催化氧化能力之间的线性关系.最新理论分析显示,该关系不仅适用于苯的氧化羟基化反应,而且也适用于异丁酸的氧化脱氢,金刚烷的硝化等反应.该构性关系的建立为进一步理解和阐释该类钒取代型的杂多阴离子簇合物参与的均相催化氧化体系奠定了良好的基础,也为催化剂的设计和催化体系的选取提供了线索.更多还原

【Abstract】 The redox properties of α-Keggin-type heteropolyanion clusters [XM12O40]n–(X = Si, P; M = Mo, W) mainly depend on their constituent outer metal-oxygen cages {M12O36}. They are just as "reservoirs", through which the transfer and transition of electrons and protons may occur. At the atomic and molecular level, the redox properties of these clusters can be controlled and also tuned by modifying the metal M on the cages and the central heteroatom X of the clusters. Combined with the experimental results, this review summarized our recent theoretical investiga-tion of the vanadium-substitution on the redox properties of the Keggin anion clusters. Theoretical modeling and calculation results showed that, the oxidative ability of the modified species was increased by partially substitution of the cage M atoms of the Keggin clusters by lower electronegativity of vanadium atoms. A linear correlation between the catalytic efficiency based on the vanadium atom and the micro-structures of the vanadium(V)-substituted heteropolyanions [PVnMo12-nO40](3+n)- (n=1–3) was established for the first time. This relationship may be suitable to interpret the catalytic behaviors of the title compounds in the benzene hydroxylation to phenol, and it’s also preferable used in the reactions of the oxidative dehydrogenation of isobutyric acid, the nitration of the adamantine, etc. The establishment of this nearly linear structure-property may lay the foundation of understanding and illustrating the behavior of the title compound in the homogeneous catalytic oxidation reactions, and may direct the catalysis design and the chosen of the catalytic reactions.更多还原