Synthesis and characterization of di-μ-oxidovanadium(V), oxidoperoxido-vanadium(V) and polymer supported dioxidovanadium(V) complexes and catalytic oxidation of isoeugenol

Abstract

The tridentate ONN donor ligand, Hbzpy-fah (I) (Hbzpy-fah=Schiff base derived from 2-benzoylpyridine and 2-furoylhydrazide) upon reaction with [VIVO(acac)2] in methanol followed by aerial oxidation give a dinuclear complex, [{VVO(bzpy-fah)}2(μ-O)2] (1) having [{VVO}2(μ-O)2]2+ core. Treatment of 1 with H2O2 in methanol results in the formation of dinuclear peroxido complex, [{VVO(bzpy-fah)}2(μ-O2)2] (2). The molecular structure of 2 was determined by single-crystal X-ray diffraction, confirming the ONN binding mode of I and μ-bis(peroxido) with side-on coordination. Reaction of 1 with imidazolomethylpolystyrene cross-linked with 5% divinylbenzene (PS-im) in DMF gives the polymer-supported complex 3 (abbreviated as PS-im[VVO2(bzpy-fah)]) which was characterized by field-emission scanning electron micrographs (FE-SEM) as well as energy dispersive X-ray (EDAX), atomic force microscopy (AFM) and thermal analysis along with usual spectroscopic techniques. Complexes 1 and 3 have been used as catalyst precursors for the oxidation of isoeugenol in the presence of aqueous H2O2 as oxidant and gave vanillin, vanillic acid and dehydrodiisoeugenol. The polymer-supported complex showed higher conversion than its neat counterpart. This has also allowed for recyclable catalytic system with increased catalyst lifetime and thus proved to be better over the homogeneous counterpart.