Synthesis of (arylimido)vanadium complexes and their application for oxidative coupling reactions of silyl enol ether derivatives

Abstract

(Arylimido)vanadium(V) complexes, V(NAr)(OEt)Cl₂ [Ar = C₆H₅, p-BrC₆H₄, p-(MeO)C₆H₄] or V(NAr)Cl₃ [Ar = o-BrC₆H₄, o-(MeO)C₆H₄] were synthesized by the reaction of VO(OEt)Cl₂ or VOCl₃, respectively, with the corresponding aryl isocyanates. X-Ray crystal structure determination for V(NAr)(OEt)Cl₂ (Ar = C₆H₅ and p-BrC₆H₄) elucidates the alkoxido-bridged dimeric building blocks [V(NAr)(OEt)Cl₂]₂, wherein the substituent on the benzene ring was found to affect the character of the imido nitrogen. The ⁵¹V NMR spectroscopic measurements indicated that the electronic state of the vanadium metal centre depends on the ligands connecting to the vanadium and the substituents on the benzene ring. The selective oxidative cross-coupling reaction of silyl ketene acetal with silyl enol ether was achieved using V(Np-BrC₆H₄)Cl₃ or V(No-BrC₆H₄)Cl₃.