Oxidovanadium complexes with tetradentate Schiff bases: Synthesis, structural, electrochemical and catalytic studies

Abstract

A series of new tridentate Schiff base ligands derived from the condensation of 4,5-dinitro-1,2-phenylenediamine and various salicylaldehyde derivatives was synthesized and characterized by common spectroscopic and analytical methods. Oxidovanadium(IV) complexes of tetradentate Schiff base ligands derived from the condensation of this diamine and salicylaldehyde derivatives were also synthesized by template method and were characterized. The crystal structures of a tridentate ligand, HL 2, and one of the complexes, VOLig 2, were determined by X-ray crystallography. HL 2 crystallizes in triclinic space group P 1 ¯ , while the VOLig 2 (which crystallizes as the DMF solvate) in monoclinic space group P2 1/ n with two [VOLig 2] DMF symmetry-independent units per asymmetric part of the unit cell. The electrochemical properties of these complexes were studied by cyclic voltammetry which shows quasi-reversible V IV/V V redox process. The new complexes are also used as catalysts for the selective oxidation of cyclooctene with tert-butylhydroperoxide (TBHP) and H 2O 2 in acetonitrile. High catalytic activities were observed and excellent selectivity was found for the epoxidation of cyclooctene.