Mixed valency in ruthenium-cyanamide systems and non-innocent behavior

INOR 408

Robert J. Crutchley, robert_crutchley@carleton.ca, Chemistry Department, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada
Recent studies (Inorg. Chem. 2006, 45, 9332 and 11035) have presented evidence suggesting that mixed-valence complexes incorporating 1,4-dicyanamidobenzene and 4,4′-azo-diphenylcyanamido dianion bridging ligands are those in which the bridging ligand is oxidized to a monoanion radical. The question of ligand or metal ion oxidation is formalism because of the unavoidable mixing of metal and ligand orbitals in a delocalized mixed-valence state. In these strongly coupled systems, partial charge is placed on bridging ligand as well as metal ions. Nevertheless, it is possible to demonstrate dominant orbital character experimentally by electronic absorption, infrared, EPR and paramagnetic NMR spectroscopies and to compare these results to theoretical predictions. The application of these techniques on dinuclear ruthenium complexes incorporating these bridging ligands is presented.