Oxidovanadium(V) Complexes Anchored on Carbon Materials as Catalysts for the Oxidation of 1-Phenylethanol

Six oxidovanadium(V) aroylhydrazone complexes derived from (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H2L1) and (3,5-di-tert-butyl-2-hydroxybenzylidene)-2-aminobenzohydrazide (H2L2), namely, [VOL1(OEt)][VOL1(OEt) (EtOH)] (1), [VOL2(OEt)] (2), [Et3NH][VO2L1] (3), [VO2(HL2)]center dot 2EtOH (4), [(VOL1)(2)(mu-O)] (5), and [(VOL2)(2)(mu-O)] (6), were synthesized and characterized by elemental analysis, IR, H-1 NMR, and V-51 NMR spectroscopies, ESI-MS and, for 1-5, single-crystal XRD. The compounds have VO3+ (1 and 2), VO2+ (3 and 4), and V2O34+ (5 and 6) cores. They are active homogeneous catalysts in the microwave-assisted, solvent-free peroxidative oxidation of 1-phenylethanol to acetophenone by tBuOOH. The immobilization of the oxidovanadium complexes (1, 2, 4, and 5) on oxidized carbon materials improved the oxidation efficiency and allowed catalyst reuse with the preservation of activity.