Peroxo‐Zr/Hf‐Containing Wells‐Dawson Polyoxometalates for H2O2‐based Homogeneous, Heterogeneous, and Biphasic Oxidation Catalysis

Abstract

AbstractFour peroxo‐Zr and Hf containing polyanions, [M2(O2)2(X2W17O61)2]16− (X=P, M=ZrIV (ZrP), HfIV (HfP); X=As, M=ZrIV (ZrAs), HfIV (HfAs) were synthesized and structurally characterized. The structures consist of two monolacunary Wells‐Dawson ions which are connected head‐on via two side‐on peroxo bridges. The four new polyanions are solution‐stable as shown by 31P NMR, Raman and FT‐IR spectroscopic studies. Comparative studies on alcohol oxidation with a solvent‐ and phase‐transfer catalyst‐free biphasic oxidative system with homogeneous and supported‐catalyst were performed and several noteworthy observations in reactivity and selectivity were observed, such as the highly selective ring‐opening oxidation of cyclohexanol to adipic acid. Tetra‐n‐butylammonium salts of ZrP and HfP were also synthesized to study the catalytic activity of the compounds in the homogenous H2O2‐based oxidation of olefins, α,β‐unsaturated carbonyl compounds, and thioethers in organic solvent.