The synthesis and structural characterization of dinuclear and triniuclear vanadium complexes

Abstract

The reactions of VCl(,2)(.)2THF and VCl(,3)(.)3THF with ligands capable of functioning as three atom bridges between metal atoms were studied. Several new dimeric and trimeric vanadium complexes in oxidation states II to IV have been synthesized and their structures determined by X-ray crystallography. The reaction of VCl(,3)(.)3THF with (2,4,6-trimethoxyphenyl)lithium yielded V(,2)(2,4,6-trimethoxyphenyl)(,4)(.)2THF. This compound was found to contain a V-V triple bond (V-V = 2.223(2)(ANGSTROM)). Two of the ligands in this complex were found to be of the expected bidentate type while the remaining pair of ligands are tridentate with a phenyl carbon positioned above the midpoint of the V-V bond. The reaction of VCl(,3)(.)3THF with sodium benzoate gave V(,3)(O)(,3)(THF)(C(,6)H(,5)CO(,2))(,6). This molecule was found to contain a planar V(,3)O trimetal moiety. The central oxygen atom is much closer (1.626(6)(ANGSTROM)) to one vanadium than to the other two (2.344(7), 2.452(6)(ANGSTROM)). Each of the other two vanadium atoms forms as exo V=O double bond. There are six bridging benzoate groups and the exo position for the first V atom is filled by a THF molecule...