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

Three new Cu(II) complexes, [Cu-4(O)(L-n)(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 center dot 0.25CH(3)CN 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 center dot 0.25CH(3)CN 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.