Synthesis, characterization and catalytic activities of vanadium complexes containing ONN donor ligand derived from 2-aminoethylpyridine

Reaction between [VIVO(acac)2] and the ONN donor Schiff base Hpydx-aepy (I) (Hpydx-aepy = Schiff base obtained by the condensation of pyridoxal and 2-aminoethylpyridine) resulted in the formation of a complex [VIVO(acac)(pydx-aepy)] (1). Addition of aqueous 30% H2O2 to 1 yields the poor stable oxidoperoxidovanadium(V) complex [VVO(O2)(pydx-aepy)] (2). Its formation has also been demonstrated in solution by treating 1 with H2O2 in methanol. Reaction of vanadium exchanged zeolite-Y with I in methanol followed by aerial oxidation gave zeolite-Y encapsulated dioxidovanadium(V) complex, abbreviated as [VVO2(pydx-aepy)]-Y (4). The crystal and molecular structure of 1 has been determined, confirming the ONN binding mode of the ligand. The encapsulated complex [VVO2(pydx-aepy)]-Y (4) catalyses the oxidation of styrene, cyclohexene, methyl phenyl sulfide and diphenyl sulfide using H2O2 as oxidant in good yield. Styrene under optimised reaction conditions gave four reaction products namely, styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol and benzoic acid while organic sulfides gave the corresponding sulfoxide as the major product. Cyclohexene gave cyclohexene epoxide, 2-cyclohexene-1-one, 2-cyclohexene-1-ol and cyclohexane-1,2-diol. Neat complex [VIVO(acac)(pydx-aepy)] has been used as catalyst precursor to compare its catalytic activities with the encapsulated one.

[VIVO(acac)(pydx-aepy)] and related complexes of Schiff base derived from pyridoxal and 2-aminoethylpyridine along with [VVO2(pydx-aepy)]-Y encapsulated in the nano-cavity of zeolite-Y are reported. These complexes have been used as catalyst for the oxidation of styrene, organic sulfides and cyclohexene.Figure optionsDownload high-quality image (105 K)Download as PowerPoint slideHighlights
► Synthesis and characterization of oxidovanadium(IV and V) complexes with new ligand derived from pyridoxal and 2-aminoethylpyridine (Hpydx-aepy).
► Structure of [VIVO(acac)(pydx-aepy)] (1) has been solved by single crystal X-ray.
► Formation of the peroxido complex in solution has also been monitored by electronic absorption spectroscopy.
► Encapsulation of [VVO2(pydx-aepy)] in the cavity of zeolite-Y and their catalytic activity for the oxidation of styrene, methyl phenyl sulfide, diphenyl sulfide and cyclohexene.
► Catalytic results are very good.