Tetranuclear copper(ii)–Schiff-base complexes as active catalysts for oxidation of cyclohexane and toluene

Abstract

Three new Cu(II) complexes, [Cu₄(O)(Lⁿ)₂(CH₃COO)₄] where HL¹ = 4-methyl-2,6-bis(2-fluoroethyliminomethyl) phenol for complex 1, HL² = 4-methyl-2,6-bis(2-chloroethyliminomethyl) phenol for complex 2·0.25CH₃CN and HL³ = 4-methyl-2,6-bis(2-bromoethyliminomethyl) phenol for complex 3 have been synthesized and characterized by elemental analysis, FTIR, UV-vis spectroscopy, and electrospray ionization mass spectroscopy. The structure of complex 2·0.25CH₃CN has also been confirmed by single crystal X-ray diffraction analysis. These complexes have been found to be active catalysts for the oxidation of cyclohexane and toluene in the presence of hydrogen peroxide as the oxidant under mild conditions. Cyclohexane is oxidized to yield cyclohexanol and cyclohexanone, whereas toluene is oxidized to benzyl alcohol and benzaldehyde.