Synthesis and characterization of some oxovanadium(V) complexes with internally functionallized oximes. Crystal and molecular structure of heptacoordinated [VOCl{ON=C(CH3) (C4H3S-2)}2] · CH3OH

Abstract

New heteroleptic oxovanadium(V) chloro oximato complexes of the type [VO{Cl}3-n{ON=C(CH3)(Ar)}n] (where Ar = C4H3O-2, C4H3S-2, C5H4N-2 and n = 1 or 2) have been synthesized in excellent yields by the reaction of VOCl3 with the sodium salts of corresponding internally functionallized oximes in refluxing anhydrous benzene. The complexes are characterized by elemental analyses and spectroscopic techniques (FT-IR, 1H-, 13C{1H}- and 51V-NMR). FAB mass spectral analysis of one of the derivatives, [VOCl{ON=C(CH3)C4H3S}2] indicates the monomeric nature of the complex. 51V-NMR spectral studies of these complexes suggest tetra-coordination around the vanadium atom in solution. However, the single crystal X-ray diffraction study of a redistribution product [VOCl{ON=C(CH3)(C4H3S-2)}2] · CH3OH obtained on recrystallization of [VOCl2{ON=C(CH3)(C4H3S-2)}] from a methanol-hexane mixture shows the vanadium(V) atom is hepta-coordinated with distorted pentagonal bipyramidal geometry. The oxo-atom occupies the axial position while the weakly coordinated CH3OH group is trans to the V=O atom. The two oximato ligands in the approximate pentagonal plane are bonded to the central vanadium atom in dihapto (η2-N, O) manner with the formation of three-membered rings. The V–Cl bond occupies the fifth position in the approximate plane.