Novel vanadium compounds with 2-pyridylbenzimidazole

• Published in: Polyhedron 2013-04, Vol.53, p.8-14
• Main Authors: Booysen, Irvin N., Hlela, Thulani, Gerber, Thomas I.A., Munro, Orde Q., Akerman, Matthew P.
• Format: Article
• Language: English
• Subjects: 2-Pyridylbenzimidazole; Bidentate; Crystal structure; Vanadium
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.01.025

The coordination behaviour of Hpybz (2-pyridylbenzimidazole) towards vanadium in various oxidation states (i.e. +III/IV/V) has been explored. A novel binuclear mixed-valence oxovanadium compound, (μ-O)[VVO(pybz)2·VIVO(Hpybz)(acac)], was obtained from the reaction of Hpybz with VO(acac)2. ESR analysis illustrates paramagnetic behaviour, typical of a type I dimer. The coordination behaviour of Hpybz (2-pyridylbenzimidazole) towards vanadium in various oxidation states (i.e. +III/IV/V) has been explored. The six-coordinate complex cis-[VVO2(Hpybz)(pybz)] (1) was isolated as the CH3OH·(H2O)2 hydrate from the reaction of NH4VO3 and Hpybz in aqueous methanol. The crystal structure shows that vanadium is bonded to two cis-oxido ligands, and to the two bidentate ligands pybz and Hpybz. This combination of ligands confers six-coordination on the metal centre, which is a rare coordination number for a mononuclear dioxido complex of vanadium(V). From the reaction between Hpybz and VCl3 the cationic complex salt cis-[VIII(OH)2(Hpybz)2]Cl (2) was formed. The ligands in 2 exhibits the same coordination behaviour as in 1, but instead of the dioxido moiety present in 1, two hydroxyl co-ligands are coordinated to the metal centre, with both chelator ligands being neutral. Conductivity measurements in DMF affirmed that the compound is a 1:1 electrolyte. A novel binuclear mixed-valence oxidovanadium compound (μ-O)[VVO(pybz)2·VIVO(Hpybz)(acac)] (3), was obtained from the reaction of Hpybz with VO(acac)2. ESR analysis illustrates paramagnetic behaviour, typical of a type I dimer. These compounds were fully characterized by means of conductance measurements, UV–Vis, IR and NMR spectroscopy and by single crystal X-ray diffraction.