Hydrogen peroxide oxidation of primary alcohols by thiosemicarbazide Schiff base metal complexes

Abstract

A series of transition metal complexes with two thiosemicarbazide Schiff bases, 1-(4-dimethylaminobenzyl- idene)thiosemicarbazide (ABTSC) and 1-(2-pyridincarboxyl-idene) thiosemicarbazide (TCTS) were synthesized with Co(II), Ni(II), Zn(II), Cd(II) and Ag(I) salts (chloride and acetate). These complexes were characterized by different methods including proton nuclear magnetic resonance (1HNMR), Fourier transform infrared (FT-IR), ultra violet visible (UV-Vis), molar conductance (λm), atomic absorption spectroscopy (AAS) and elemental analysis (CHNS). All complexes were applied as a catalyst for oxidation of aromatic alcohols. The effects of reaction time, temperature, catalyst amount, oxidant and solvents were investigated in detail. The oxidation of alcohols occurs effectively and selectively with H2O2 as the oxidant. For instance, 4-Methoxybenzyl alcohol is oxidized to the corresponding aldehyde with 95% conversion and 100 % benzaldehyde selectivity under the optimum conditions.