A comparative study on Keggin and Wells–Dawson sandwich type polyoxometallates in the oxidation of alcohols with 30% hydrogen peroxide

The tetra-n-butylammonium (TBA) salts of Keggin and Wells–Dawson sandwich type polyoxotungstates, [M4(PW9O34)2]m− and [M4(P2W15O56)2]n− (M = Mn2+, Fe3+, Co2+, Ni2+ and Zn2+), proved to be effective catalysts for the oxidation of benzylic alcohols to the corresponding aldehydes with 30% hydrogen peroxide in acetonitrile. The Wells–Dawson type polyoxometallates showed lower activity than the Keggin ones, and both the Zn substituted polyoxometallates depicted higher conversions. Oxidation of different benzylic alcohols with electron withdrawing and electron donating substituents gave high to excellent yields in the presence of Zn substituted POMs.

The TBA salts of [M4(PW9O34)2]m− and [M4(P2W15O56)2]n− were used as effective catalysts for the selective oxidation of benzylic alcohols. The Wells–Dawson type polyoxometallates were shown to be less active than the Keggin ones and the Zn substituted polyoxometallates depicted higher conversions for both types.Figure optionsDownload as PowerPoint slide