Dimeric Ruthenium Complexes of Dicyanopyrazines: Complexes with an Unstable Mixed-Valence State
Eric C. Kesslen, William B. Euler, Polyhedron, 1992, 11, 3109 – 3115
Abstract
Pentaammineruthenium complexes bridged by 2,3-dicyanopyrazine and 2,3-dicyano-5,6-dimethylpyrazine have been prepared and characterized. The bridging ligand binds to the metal atoms through the cyano nitrogen. Complexes can be prepared in the +4 and +6 oxidation states but the mixed-valence, +5, state is not observed experimentally, unlike the previously prepared 1,2-dicyanobenzene dimer, which does have a stable +5 state. A simple electronic model is constructed from the spectroscopic data and is used to show that the electronic perturbations caused by the uncomplexed nitrogen atoms in the pyrazine ring are sufficient to drive the disproportionation reaction of the +5 state.