Some ternary complexes of oxovanadium(IV) with acetylacetone and N-(2-pyridyl)-N′-(salicylidene)hydrazine and its derivatives

The reactions of one equivalent each of [VO(acac)(2)] and N-(2-pyridyl)-N'-(5-R-salicylidene)hydrazines (HphsalR) (derived front 2-hydrazinopyridine and 5-substituted salicylaldehydes) in boiling acetonitrile under aerobic conditions provide ternary complexes of oxovanadium(IV) having the general formula [VO(phsalR)(acac)]. The complexes have been characterized by analytical, magnetic and spectroscopic measurements. The structures of two representative complexes have been determined by X-ray crystallography. In each structure, the metal centre is in a distorted octahedral N2O4 coordination sphere. The tridentate phsalR(-) coordinates the metal ion via the pyridine-N, the imine-N and the phenolate-O atoms in a meridional fashion. The remaining three coordinations sites are occupied by the bidentate O,O-donor acetylacetonate (acac(-)) and the oxo group. In the crystal lattice, the molecules of each of the two complexes assemble to form one-dimensional supramolecular structure via intermolecular N-H center dot center dot center dot O=V hydrogen bond interaction. Electronic spectra collected using dimethylsulfoxide solutions of the complexes display a weak absorption within 643-720 nm due to d-d transition and some strong absorptions in the range 510-262 nm due to ligand-to-metal charge transfer and ligand centred transitions. The room temperature (298 K) effective magnetic moments of the complexes in the solid state are consistent with an S = 1/2 ground state of the metal ion in each complex. All the complexes display axial EPR spectra with well-resolved V-51 hyperfine structure characteristic of an axially compressed octahedral coordination geometry around the metal centre. (C) 2005 Elsevier Ltd. All rights reserved.