Synthesis, structural characterization, encapsulation in zeolite Y and catalytic activity of an oxidovanadium(V) complex with a tribasic pentadentate ligand

Abstract

Reaction of [VIVO(acac)2] with H3hap-dahp (I: Schiff base derived from 2-hydroxyacetophenone and 1,3-diamino-2-hydroxypropane) in methanol under aerobic conditions resulted in the formation of the complex [VVO(hap-dahp)] (1). Treatment of I with vanadium(IV) exchanged zeolite Y followed by aerial oxidation gave the encapsulated oxidovanadium(V) complex [VVO(hap-dahp)]-Y (2) in the nanocavity of zeolite Y. Elemental analysis, spectroscopic (IR, electronic, 1H and 51V NMR) studies, scanning electron micrographs and X-ray diffraction patterns have been used to characterize these complexes, which have a distorted octahedral structure, confirming the tribasic O3N2 binding mode of the ligand. The encapsulated complex [VVO(hap-dahp)]-Y (2) catalyzes the oxidation of styrene, methyl phenyl sulfide and diphenyl sulfide using H2O2 as an oxidant in good yield (82%, 98% and 81%, respectively). Styrene, under optimized reaction conditions, gave five reaction products, namely styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while the organic sulfides gave the corresponding sulfoxides as the major product. The neat complex [VVO(hap-dahp)] (1) also exhibits good catalytic activity for these substrates. The encapsulated complex showed a good recycling ability.