Chiral dioxovanadium(V) complexes with single condensation products of 1,2-diaminocyclohexane and aromatic o-hydroxycarbonyl compounds: Synthesis, characterization, catalytic properties and structure

New dioxovanadium(V) complexes bearing tridentate products of single condensation of RR(−) and of SS(+)-1,2-diaminocyclohexane with salicylaldehyde and its derivatives, 2-hydroxy-1-naphthaldehyde and 1-hydroxy-2-acetonaphthone, have been synthesized. The crystal structure of the {RR(−)-1-amino-2-N-[1′-(1″-oxido-κO-2″-naphthyl)ethylidene]aminocyclohexane-κ2N}dioxovanadium(V) hemihydrate hemiethanol solvate, determined by X-ray analysis, is characterized by trigonal bipyramidal coordination geometry of complex molecules which are linked to solvent molecules by hydrogen bonds to form chains. The cyclohexane ring is in chair conformation with a very small distortion towards half-chair and envelope forms. Complexes were characterized by UV–Vis, FTIR, 1H, 13C, 51V NMR and CD spectroscopies. CD spectra of {RR(−)-1-amino-2-N-[(2′-oxido-κO-5′-nitrophenyl)methylene]aminocyclohexane-κ2N}dioxovanadium(V) and of R(−)-1,2-diaminopropane analogue do not bear mirror image relationship in contrast to V(IV and V), Cu(II) and Ni(II) complexes containing double condensed diamines in the same absolute configurations. 1H and 13C NMR resonance signals of all complexes dissolved in DMSO were assigned. The complexes bearing the methoxy substituent in position 3 or 5 of the aryl group catalyse the oxidation of methyl phenyl sulfide by cumene hydroperoxide to the corresponding sulfoxide with reasonable enantiomeric excesses (19–23%).

Eighteen new chiral VO2L complexes where L is the deprotonated product of single condensation of RR(−)-1,2-diaminocyclohexane or of SS(+)-1,2-diaminocyclohexane with aromatic hydroxyaldehyde or ketone, were synthesized and characterized by various spectroscopic methods. Crystal structure of the complex derived from 1-hydroxy-2-acetylonaphtalene and RR(−)-1,2-diaminocyclohexane was determined. Complexes bearing methoxy substituent in position 3 or 5 of the aryl group act as catalyst in the oxidation of prochiral methyl phenyl sulfide to the corresponding sulfoxide.Figure optionsDownload as PowerPoint slide