Oxidation of phenol, styrene and methyl phenyl sulfide with H 2O 2 catalysed by dioxovanadium(V) and copper(II) complexes of 2-aminomethylbenzimidazole-based ligand encapsulated in zeolite-Y

Abstract

Interaction of oxovanadium(IV) exchanged zeolite-Y with the Schiff base derived from salicylaldehyde and 2-aminomethylbenzimidazole (Hsal-ambmz) in refluxing methanol followed by aerial oxidation leads to the formation of encapsulated dioxovanadium(V) complex, [VO 2(sal-ambmz)]-Y( 1). Similar reaction with copper(II) exchanged zeolite-Y followed by its treatment with aqueous NaCl gave encapsulated copper(II) complex, [Cu(sal-ambmz)Cl]-Y( 2). These encapsulated complexes have been characterized by spectroscopic studies, thermal analysis and scanning electron micrographs (SEMs) as well as X-ray diffraction patterns. 3D model structure generated for neat complex [VO 2(sal-ambmz)] suggests that zeolite-Y can accommodate these complexes in its nano-cavity without any strain. The encapsulated materials are active catalysts for the oxidation of phenol, styrene and methyl phenyl sulfide using H 2O 2 as an oxidant. Under the optimised reaction conditions about 42% conversion of phenol was obtained with these catalysts where the selectivity of catechol varied in the order: 2 (73.9%) > 1 (65.2%). With the conversion of 97.0% with 1 or 56.7% with 2, the oxidation of styrene gave styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde as major products. A maximum of 96.1% (with 1) conversion of methyl phenyl sulfide was observed in which the selectivity of major product methyl phenyl sulfoxide was found to be ca. 98%.