Oxido-bridged dinuclear vanadium(V) Schiff base complexes derived from 1R,2S(−)-norephedrine: Synthesis, structure, characterization and catalytic studies

Abstract A series of vanadium(V) complexes with chiral tridentate Schiff base ligands, obtained by a single condensation of 1R , 2S (−)-norephedrine with salicylaldehyde and its derivatives, were prepared. The complexes were characterized by elemental analysis and by their IR, CD, UV–Vis, 1D ( 1 H, 51 V) and 2D (COSY, gHSQC) NMR spectra. The X-ray analysis of μ -oxido-bis({ 1R , 2S (−)-2-[(1-oxido-1-phenylpropyl)iminomethyl]-3,5-dimethoxyphenolato- κ 3 N , O , O ′}oxidovanadium(V)), V 2 O 3 (C 18 H 19 NO 4 ) 2 , 4 , 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 V V –O–V V angle of 108.75(8)° and V–O distances of 1.802(2) and 1.818(2) A. 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% H 2 O 2 or cumene hydroperoxide (CHP) as oxidant.