Vanadium(V) complexes of O,N,O-donor tridentate ligands containing the {V(v)O(OMe)}2+ unit:: Syntheses, structures and properties

Syntheses, characterisation and properties of two complexes containing the oxovanadium(V) methoxide unit have been described. Deprotonated benzoylhydrazones of 2-hydroxy-5-methoxybenzaldehyde (H(2)bhsOMe) and 2-hydroxy-5-chlorobenzaldehyde (H(2)bhsCl) were used as coligands. Crystal structures of both the complexes were determined. In solid state one of them is a dinuclear species [VO(bhsOMe)(OMe)](2) (1) whereas the other one is a mononuclear complex [VO(bhsCl)(OMe)(HOMe)] (2). The dinegative ligands coordinate the metal ions via phenolate-O, imine-N and deprotonated amide-O atoms. In 1, the metal ions of two square pyramidal VO(bhsOMe)(OMe) units share the methoxide groups to form a dinuclear species. The oxygen of a methanol molecule completes the hexacoordination of the metal centre in 2. In each of the two distorted octahedral VO5N moieties of 1 the bridging methoxide oxygen and in that of 2 the methanol oxygen is Irans to the corresponding oxo group. Both the complexes are redox active, The VO3+ to VO2+ reduction potentials (vs Ag/AgCl) of 1 and 2 are observed at -0.25 and -0.04 V, respectively. The band positions in the electronic spectra and the redox potentials reflect the influence of the substituents present on the ligands.