Oxidovanadium(V) complexes with chiral tridentate Schiff bases derived from R(−)-phenylglycinol: Synthesis, spectroscopic characterization and catalytic activity in the oxidation of sulfides and styrene
Abstract A series of vanadium(V) complexes with chiral tridentate Schiff base ligands, obtained by the single condensation of R(−)-phenylglycinol with salicylaldehyde and its derivatives, were prepared. The complexes were characterized by elemental analysis and by their ESI-MS, IR, CD, UV–Vis, 1D (1H, 51V) and 2D (COSY, gHSQC) NMR spectra. The vanadium(V) complexes have the ability to catalyze the oxidation of sulfides [PhSR (R = Me, Bz)] in excellent yields and enantiomeric excesses (over 90%), utilizing aqueous 30% H2O2 or cumene hydroperoxide (CHP) as the oxidant. These complexes are also catalytically active in the oxidation of styrene, using aqueous 30% H2O2 or tert-butyl hydroperoxide (TBHP) as the oxidant, to styrene oxide, benzaldehyde, benzoic acid, phenylacetaldehyde and 1-phenylethane-1,2-diol.