Dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases encapsulated in zeolite-Y for the aerobic oxidation of styrene

Abstract

A series of dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases were encapsulated into the supercages of zeolite-Y and were characterized by X-ray diffraction, SEM, N₂ adsorption/desorption, FT-IR, UV-vis spectroscopy, ICPAES, pair distribution function (PDF) and X-ray absorption near edge structure (XANES) measurements. The encapsulation is achieved by a flexible ligand method in which the transition metal cations were first ion-exchanged into zeolite-Y and then complexed with ligands. The dioxovanadium-exchanged zeolite, dioxovanadium complexes encapsulated in zeolite-Y plus non-encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes showed better activity than their respective nonencapsulated counterparts in most cases. All encapsulated dioxovanadium tetrahydro-Schiff base complexes showed much higher activity in aerobic oxidation of styrene than their corresponding Schiff base complexes.