A comparative study of different metal acetylacetonates covalently anchored onto amine functionalized silica: a study of the oxidation of aldehydes and alcohols to corresponding acids in water

A series of metal acetylacetonates covalently anchored onto amine functionalized silica were prepared by the complexation of metal acetylacetonates [Co(acac)2, Cu(acac)2, Pd(acac)2, Ru(acac)3, Mn(acac)3, Co(acac)3] with organically modified 3-aminopropyl silica and their catalytic activities were tested for the oxidation of aromatic aldehydes, α,β-unsaturated aldehydes and benzyl alcohols to the corresponding carboxylic acids in aqueous medium. Different metal acetylacetonates have been chosen with a view to select the most active heterogeneous catalyst for oxidations. The characterization of the catalysts was done on the basis of FTIR, TGA and AAS analysis. SiO2–Co(acac)2 catalyzes the oxidation of aromatic aldehydes under air atmosphere without using any additional oxidant; however, t-BuOOH was found to be a highly efficient oxidant for the oxidation of α,β-unsaturated aldehydes and heterocyclic aldehydes, as well as the direct oxidation of benzyl alcohols to the corresponding carboxylic acids. The most active catalyst was found to be highly stable and recyclable under the reaction conditions.