Covalently anchored metal complexes onto silica as selective catalysts for the liquid phase oxidation of benzoins to benzils with air

Benzoins are selectively oxidized to benzils in the presence of covalently anchored metal complexes onto silica by stirring in toluene at 100 °C in air atmosphere. Silica functionalized metal complexes have been prepared by the complexation of organically modified silica (imine) with Pd(OAc)2 (Cat 1), Co(OAc)2 (Cat 2) and Ni(OAc)2 (Cat 3). Cat 1, 2 and 3 have been characterized by FTIR, thermal analysis and AAS analysis. Cat 1 was found to be most active, stable and recyclable under the reaction conditions. It was also characterized by SEM and TEM.