Chiral oxidovanadium(V) complexes with tridentate Schiff bases derived from S(+)-2-amino-1-propanol: Synthesis, structure, characterization and catalytic activity

Abstract

A series of vanadium(V) complexes with chiral tridentate Schiff base ligands, obtained by a single condensation of S(+)-2-amino-1-propanol with salicylaldehyde and its derivatives, were prepared. The complexes were characterized by elemental analysis and by their IR, CD, UV–Vis, 1D (1H, 51V) and 2D (COSY, gHSQC) NMR spectra. The X-ray analysis of μ-oxido-bis({S(+)-2-[(1-oxidopropyl)iminomethyl]-4-nitrophenolato-κ3N,O,O′}oxidovanadium(V)), V2O3(C10H10N2O4)2, 7, revealed oxido-bridged dinuclear structure with, unexpectedly, two five-coordinate square-pyramidal geometries about metal atoms. The two O-bonded oxidovanadium units are in the twist-angular configuration with the VV–O–VV angle of 107.05(11)° and V–O distances of 1.794(2) and 1.826(2)Å. The vanadium(V) complexes have ability to catalyze the oxidation of sulfides [PhSR (R=Me, Bz)] in good yields and enantiomeric excesses, utilizing aqueous 30% hydrogen peroxide or cumene hydroperoxide (CHP) as oxidant.