OXOVANADIUM(IV) COMPLEXES WITH TRIDENTATE DIBASIC SCHIFF-BASE LIGANDS AND 2-(2'-PYRIDYL)BENZIMIDAZOLE

Several tridentate dibasic schiff base ligands with ONO donor set react with VO(OAc)2 in presence of the neutral bidentate ligand 2-(2'-pyridyl)benzimidazole (PBH) containing NN donor set to form monomeric and six-coordinated complexes of the type [VO(SB) (PBH)] (H2SB = tridentate schiff bases). These are orange to brown coloured paramagnetic solids with normal magnetic moments. All the complexes exhibit a strong IR band at 960 cm-1 due to v(V = O). Their EPR spectra are characterised by a single unresolved signal at g = 2.00 +/- 0.02. Electrochemical measurements are characterised by oxidation to vanadium(V) and reduction to vanadium(III) at + 0.98 to + 1.26 V vs SCE and - 1.08 to - 1.50 V vs SCE, respectively. The thermogravimetric measurements indicate the stability of the complexes and their stepwise thermal decomposition finally giving V2O5 as the end product.