Synthesis and redox properties of trinuclear ruthenium and osmium complexes containing 2,2′-biimidazolate as bridging ligand

A series of trinuclear complexes of ruthenium and osmium containing the terminal ligands 2-(phenylazo)pyridine (pap), triphenyl phosphine (PPh3) and the bridging ligand 2,2'-biimidazolate (biim(2-)) have been synthesised. These are characterised by the analyses of their physicochemical data. Electron spray ionization mass spectrum of one representative compound has been reported which authenticates the formulation of the compound. Cyclic voltammetric studies on the above trinuclear complexes are reported. These undergo three successive metal centered one electron transfer processes. The half-wave potentials for the oxidation processes are dependent largely on the electrochemical parameters of the coordinating ligands. Partial oxidation of the trinuclear complexes led to unsymmetrical bridge cleavage reaction. In addition to the above metal oxidation processes the above complexes showed multiple ligand reduction responses at the negative of the Ag-AgCl reference. (C) 1999 Elsevier Science Ltd. All rights reserved.