Mononuclear and dinuclear chiral vanadium(V) complexes with tridentate Schiff bases derived from R(−)-1,2-diaminopropane: Synthesis, structure, characterization and catalytic properties

Abstract

A series of vanadium(V) complexes with unsymmetrical tridentate Schiff base ligands, obtained by the single condensation of R(−)-1,2-diaminopropane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde, 2-hydroxyacetophenone, 1-hydroxy-2-acetonaphthone and 2-hydroxybenzophenone, were prepared. The complexes were characterized by elemental analysis and by their IR, CD, UV–Vis, 1D ( 1H, 51V) and 2D (COSY, NOESY, gHSQC) NMR spectra. Crystal structures of the mononuclear complex { R(−)-2-amino-1- N-[(2′-oxido-κ O-4′,6′-dimethoxyphenyl)methylene]aminopropane-κ 2 N}dioxidovanadium(V), VO 2(C 12H 17N 2O 3), 4, and of the dinuclear complex, di-μ-oxido-bis({ R(−)-2-[1-(2-aminopropylimino)ethyl]-4-methylphenolato-κ 3 N, N′, O}oxidovanadium(V)), V 2O 4(C 11H 15N 2O) 2, 5, have been obtained by X-ray diffraction studies. The structure of 4 was revealed to be a distorted trigonal–bipyramidal coordination geometry, rarely encountered in VO 2(tridentate Schiff base) complexes. Complexes 2 and 3 have the ability to catalyze the oxidation of prochiral sulfide substrates PhSR (R = Me, Bz) utilizing hydrogen peroxide or cumene hydroperoxide (CHPO) as the oxidant.