Alkoxide ligand controlled self-assembling of (imido)vanadium(V) compounds having a tetrahedral VO3N geometry.

The reaction of (1S,2S)-(-)-1,2-diphenylethylenediamine with VO(OiPr)3 in the presence of NaH was found to afford the binuclear (imido)vanadium(V) triisopropoxide, [(OiPr)3V(N-meso-1,2-DPE-N)V(OiPr)3] (DPE = diphenylethylene), (1aRS/SS). Using (1R,2R)-(+)-1,2-diphenylethylenediamine as a starting material, one-step reaction also proceeded to form the binuclear (imido)vanadium(V) triisopropoxide, [(OiPr)3V(N-meso-1,2-DPE-N)V(OiPr)3], (1aRS/RR). The single-crystal X-ray structure determination of 1aRS/SS revealed the hydrogen-bonded self-assembled structure utilizing the advantage of anti-conformation through the intermolecular hydrogen bonds of C-H···O pattern between phenyl and isopropoxide moieties, wherein each vanadium atom is coordinated in a nearly tetrahedral VO3N geometry (τ4 = 0.017 and 0.057). On the contrary, a discrete (imido)vanadium(V) tris(triphenylsiloxide) unit, which possesses a nearly tetrahedral VO3N arrangement around the vanadium metal center (τ4 = 0.060), was observed in the crystal structure of the (4-methoxyphenylimido)vanadium(V) tris(triphenylsiloxide), [(p-MeOC6H4N)V(OSiPh3)3], (1b) with bulky triphenylsiloxide ligands.

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

(Arylimido)vanadium(v) complexes, V(NAr)(OEt)Cl(2) [Ar = C(6)H(5), p-BrC(6)H(4), p-(MeO)C(6)H(4)] or V(NAr)Cl(3) [Ar = o-BrC(6)H(4), o-(MeO)C(6)H(4)] were synthesized by the reaction of VO(OEt)Cl(2) or VOCl(3), respectively, with the corresponding aryl isocyanates. X-Ray crystal structure determination for V(NAr)(OEt)Cl(2) (Ar = C(6)H(5) and p-BrC(6)H(4)) elucidates the alkoxido-bridged dimeric building blocks [V(NAr)(OEt)Cl(2)](2), wherein the substituent on the benzene ring was found to affect the character of the imido nitrogen. The (51)V 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-BrC(6)H(4))Cl(3) or V(No-BrC(6)H(4))Cl(3).

Structural characterization and self-association of (Arylimido)vanadium(V) triisopropoxides.

(Arylimido)vanadium(V) triisopropoxides, [( p-RC 6H 4N)V(O (i) Pr) 3] (R = NMe 2, OMe, H, CN, NO 2, Br), were prepared by the reaction of VO(O (i) Pr) 3 with the aryl isocyanates without solvent. The structures of the (arylimido)vanadium(V) triisopropoxides were characterized by single-crystal X-ray structure determination to elucidate the substituent effect on the self-association properties. Controlled association of the (arylimido)vanadium(V) triisopropoxides to the mu-oxo-bridged dimer complexes or the mu-imido-bridged dinuclear complex was achieved by changing the p-substituent on the benzene rings, which regulates the nature of the imido bonds. Furthermore, the one-dimensional linear polymer complex or the one-dimensional zigzag one through mu-oxo-bridging was formed in a solid state with the bimetallic (arylimido)vanadium(V) complex, [( (i) PrO) 3V(N- p-C 6H 4N)V(O (i) Pr) 3] or [( (i) PrO) 3V(N- m-C 6H 4N)V(O (i) Pr) 3], respectively.