Ligand reactivity, substituent effects and solvent interactions in the spectra and structure of some oxovanadium(V) chelates with Schiff bases. Proof for dimeric species

The reaction of bis(β-dionato)oxovanadium(IV) chelates, VOβ2, with substituted benzoylhydrazines, XbhH2, was explored in alcoholic solutions and oxovanadium(V) compounds with Schiff bases as ligands were obtained in high yield. These VOL(OR) compounds have alkoxide as coligand and the asymmetic tridentate Schiff base ligands, L2−, bind to the oxovanadium core through the carbonyl oxygens and the imine nitrogen. Substituents attached to benzoylhydrazines affect the electron density about the oxovanadium core. While electron attracting substituents appear to favour monomeric square pyramidal chelates, the derivatives having electron repelling groups seem to encourage formation of dimeric structures and alkoxo bridged dimers are obtained. The crystal structures of the products of the reaction of bis(1-phenyl-1,3-butanedionato)oxovanadium(IV), VO(bzac)2, with o-nitrobenzoylhydrazine (o-O2NbhH2) and m-methoxybenzoylhydrazine (m-CH3ObhH2) that are reported demonstrate the influence of the substituents as well as the role of the solvent.