Intervalence Absorption, Ligand Interchange, and Redox Reactivity in Binuclear Cyanopyridine-Bridged Complexes Containing Pentacyanoruthenate(II) and Pentaammineruthenium(II) or -(III)

The fully reduced [(NC)5RuII(4-pyCN)RuIIA5]- (R) and the mixed-valence [(NC)5RuII(4-pyCN)RuIIIA5] (M) complexes were prepared in aqueous solution and were isolated as solid compounds (4-pyCN) = 4-cyanopyridine; A = ammine). Both complexes showed the corresponding MLCT transitions to the π* orbital of bridging pyCN, and M showed an intervalence band at 700 nm (ε = 500 M-1 cm-1). From the latter results, the electronic coupling and the delocalization factors were calculated: Hab = 345 cm-1 and α2 = 5 × 10-4. Kinetic data were obtained for the formation and dissociation reactions of R and M, as well as for the oxidation reaction of R with peroxydisulfate. The M complex was susceptible to hydrolysis at the Ru(III)−NC bond.