SIMPLIFIED PREPARATIONS AND ELECTROCHEMICAL-BEHAVIOR OF 2 CHROMIUM-SUBSTITUTED HETEROPOLYTUNGSTATE ANIONS

Simplified preparative procedures are described for the generation of alpha-[PW11O39Cr(III)(OH2)]4- and alpha2-[P2W17O61-Cr(III)(OH2)]7-anio ns which can be readily oxidized, chemically or electrochemically, to alpha-[PW11O39Cr(V)O]4- and alpha2-[P2W17O61Cr(V)O]7-. The oxidized co mplexes are stable in aqueous solutions. They react with benzyl or eth yl alcohol, but the rates of the oxidations are too slow to make the C r(V) derivatives attractive as electrocatalysts. The voltammetry of th e Cr(V)/Cr(III) couples is only quasi-reversible, but approximate form al potentials with their pH dependencies are reported. Diffusion coeff icients evaluated for the polyanions show the larger anion to diffuse more slowly and neither anion to be highly hydrated.