Oxidation of phenol, styrene and methyl phenyl sulfide with H2O2 catalysed by dioxovanadium(V) and copper(II) complexes of 2-aminomethylbenzimidazole-based ligand encapsulated in zeolite-Y

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, [VO2(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 [VO2(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 H2O2 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%.

Dioxovanadium(V) and Copper(II) complexes of Schiff bases derived from salicylaldehyde and 2-aminomethylbenzimidazole have been encapsulated in the cavity of zeolite-Y and characterized. These complexes catalyse the oxidation, by peroxide, of phenol, styrene and methyl phenyl sulfide in good yield. Figure optionsDownload as PowerPoint slide