Binuclear ruthenium complexes bridged by the dicyanamide anion

Article abstract of DOI:10.1021/ic00137a059

As shown by the value of the extinction coefficient for the intervalence band for μ-dicyanamido-bis(pentaammineruthenium)(4+), ε 2.8 × 10³ M^-1 cm^-1, dicyanamide ion as a bridging group produces quite strong electronic coupling in the mixed-valence molecule. A number of properties, among them the bandwidth at half-height, the dependence of the band energy on solvent properties, and the rather small value of the comproportionation constant, 3.4 × 10², show the species to be valence trapped. Replacing trans ammonias by pyridine or by isonicotinamide decreases the electronic coupling, suggesting that the dominant coupling mechanism, in spite of the negative charge on the ligand, is πd-π* delocalization rather than πd-π.