Investigation of the manganese-substituted α-Keggin-heteropolyanion K 6SiW 11O 39Mn(H 2O) by cyclic voltammetry and its application as oxidation catalyst

Abstract

The behavior of a manganese substituted α-Keggin silicon tungstoheteropolyanion (K 6SiW 11O 39Mn(II)(H 2O)) under electrochemical oxidation conditions was investigated by means of cyclic voltammetry in phosphate buffer. Substitution of the water ligand by counter anions (L: H 2PO − 4 or HPO 2− 4) leading to SiW 11O 39Mn(II)(L) was observed. Replacement of the counter anion by an aquo ligand was observed in cyclic voltammetry by continuous cycling. After oxidation of SiW 11O 39Mn(II)(L) to SiW 11O 39Mn(IV)(L), this counter anion L was in turn substituted by OH −. The thus formed complex SiW 11O 39Mn(IV)(OH) oxidizes different alcohols, the reactivity of which decreases as follows: 1-phenyl-ethanol, benzylalcohol > iso-propanol > ethanol.