Polyoxometalate coordinated transition metal complexes as catalysts: Oxidation of styrene to benzaldehyde/benzoic acid

Abstract

Oxidation of styrene is carried out by using heptamolybdate coordinated transition metal (Co2+, Zn2+) complexes, [2-ampH]4[{Co(H2O)5}Mo7O24] ·9H2O (1), [3-ampH]4[{Co(H2O)5}Mo7O24] ·9H2O (2), [2-ampH]4[{Zn(H2O)5}Mo7O24] ·4H2O (3) and [3-ampH]4[{Zn(3-ampy)(H2O)4}Mo7O24] ·4H2O (4) as catalysts and H2O2 as an oxidant at 80°C. The leaching study has been carried out to check the quality of catalyst and it has been reused for three times with good percentage of conversion. For the first two catalysts (compounds 1 and 2), the major product obtained is benzaldehyde, and benzoic acid is the major product for next two catalysts (compounds 3 and 4). Stability of the catalysts has been analyzed by IR, UV-spectroscopy and powder X-ray crystallography.