Abstract

The reaction of [Ni(tmhd)<inf>2</inf>] and [Ni(dbm)<inf>2</inf>] with N-donor chelating ligands in dichloromethane and acetone, respectively, yields the complexes [Ni(tmhd)<inf>2</inf>(L-L)] (L-L = 2,2′-bpy 1, phen 2 and dmae 3) and [Ni(dbm)<inf>2</inf>(L-L)] (L-L = 2,2′-bpy 4, phen 5, dmae 6). UV-Vis spectroscopy shows very strong bands in the UV region consistent with ligand centred π → π^* transitions. The electrochemical studies of 1-6 reveal oxidation to Ni(III). The [Ni(tmhd)<inf>2</inf>(L-L)] 1-3 are more easily oxidized by ca. 300 mV and are quasi-reversible whereas for the [Ni(dbm)<inf>2</inf>(L-L)] series only complex 6 shows significant reversibility. X-ray crystallographic studies have been conducted in the case of [Ni(dbm)<inf>2</inf>(phen)] 5 and [Ni(dbm)<inf>2</inf>(dmae)] 6. The structures both show that the nickel metal centre is octahedral with an O<inf>4</inf>N<inf>2</inf> coordination environment. In the structures the β-diketonate ligands exhibit a cis-arrangement, with the metal displaced out of the planar chelate ring. © 2008 Elsevier B.V. All rights reserved.