Chemistry of hydrazonato oxovanadium(V) alkoxides derived from dihydric/monohydric alcohols

Abstract

The reaction of bis(acetylacetonato)oxovanadium(IV) with benzoylhydrazones of benzoylacetone and salicylaldehyde — H2babh and H2sabh, respectively — with ethane-1,2-diol (H2ed) in acetone solution has afforded the alkoxides VVO(babh)(Hed) and VVO(sabh)(Hed) in which the Hed− ligand is chelated both in the solid state and in solution. In methanol solution (no H2ed added) five-coordinated VvO(babh)(OMe) and six-coordinated VVO(sabh)(OMe)(OHMe) are formed. Aerial oxygen is the oxidant (VIV → VV) in the synthesis. The X-ray structures of VO(babh)(Hed) and VO(sabh)(OMe)(OHMe) are reported. In the VO5N coordination sphere the alcohol oxygen lies trans to the oxo oxygen. The general VO bond length order is oxo < alkoxidic < phenoxidic < enolato < alcoholic. The complexes are mononuclear but intermolecular OH…N hydrogen bonding afford dimers. The Hed− complexes represent authentic examples of rare oxovanadium species incorporating ethane-1,2-diol chelation uncomplicated by alkoxide bridging. The complexes have low V(V)/V(IV) reduction potentials () corresponding to stabilization of the pentavalent state. The methylene protons of Hed− in the complexes are inequivalent in solution (1H NMR). Crystal data: VO(babh)(Hed): monoclinic, space group