Synthesis, characterization and crystal structure determination of a new vanadium(IV) Schiff base complex (VOL2) and investigation of its catalytic activity in the epoxidation of cyclooctene

Abstract

The vanadium(IV) Schiff base complex VOL2, L=2-{(E)-[2-chloroethyl)imino]methyl}-6-methoxy phenol, has been synthesized by the reaction of a methanolic solution of VO(acac)2 with a methanolic solution of the Schiff base ligand, and it has been characterized using single-crystal X-ray crystallography, elemental analysis (CHN) and FT-IR spectroscopy. The crystal structure determination of this complex shows a deformed tetragonal pyramidal N2O3 coordination sphere of the vanadium center. The Schiff base ligand acts as a bidentate ligand with the two phenolato oxygen atoms and the two imine nitrogen atoms in trans positions. Non-classical inter- and intra-molecular hydrogen bonds of the type CH⋯O have been found in the structure, the latter connecting the monomeric VOL2 units. The catalytic activity of the VOL2 Schiff base complex in the epoxidation of cyclooctene was investigated using different reaction parameters, such as solvent effect, oxidant, alkene/oxidant ratio and the catalyst amount. The results showed that with a catalytic amount of the VOL2 Schiff base complex and a 1:3 ratio of the cyclooctene/TBHP, the cyclooctene was effectively and selectively converted into the corresponding epoxide with CHCl3 as the solvent.