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

摘要

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-κO-4′,6′-dimethoxyphenyl) methylene]aminopropane-κ~2N}dioxidovanadium(V), VO _2(C_(12)H_(17)N_2O_3), 4, and of the dinuclear complex, di-μ-oxido-bis({R(-)-2-[1-(2-aminopropylimino)ethyl]- 4-methylphenolato-κ~3N,N′,O}oxidovanadium(V)), V _2O_4(C_(11)H_(15)N_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.