SUBSTITUTION AND STABILITY EFFECTS IN HETEROPOLYACIDS - A THEORETICAL ANALYSIS OF THE DIVERSITY OF THE KEGGIN ION

摘要

In this work, the redox effects and stability of a series of analogous [X((n))Mo12O40]((8-n)-) and [X((n))W12O40]((8-n)-) heteropolyanions are assessed. Both of these homologs display the alpha-Keggin structure in which a tetrahedral oxyanion helps to satisfy the coordination sphere of the metal oxide octahedron of the clathratic shell. Here, results from a series of semiempirical electronic-structure calculations are used to illustrate the electronic effects induced by chemical modifications. The stability trends produced in this work reliably trace the experimental trends and present the description of electronic features required for stabilization of the Keggin ion. In addition, understanding these electronic effects induced by chemical modification is critical in the rational design of heteropolymetallate catalysts. (C) 1995 Academic Press,Inc. [References: 40]