Properties of the mixed-valence binuclear complex ion, (NH 3) 5Ru III-NC-Os II(CN) 5] −

Abstract

The mixed-valence ion, [(NH 3) 5Ru III-NC-Os II(CN) 5] −, was prepared in solution from [Ru(NH 3) 5H 2O] 3+ and [Os(CN) 6] 4− and was isolated as a potassium salt. A kinetic study of the formation reaction shows that a dissociative mechanism is operative, the process being rate-controlled by the loss of water from the Ru(III) moiety, as in related reactions with [Fe(CN) 6] 4− and [Ru(CN) 6] 4−. The binuclear ion shows a distinctive intervalence band, associated to charge transfer from Os(II) to Ru(III), at 830 nm (ϵ=3450 M −1 cm −1), with a noticeable asymmetry, probably associated to spin-orbit coupling. Shifts in the redox potentials at the metal centers on dimer formation are consistent with the Os(II)-Ru(III) formulation. By measuring solution Raman spectra in post-resonance conditions with respect to the IT band, activation of the bridging CN stretching, as well as of the terminal stretching modes, is observed; absolute distortion values for both of the modes can be calculated by applying a time-dependent analysis of the scattering problem. IR and Raman results of the solid samples are also presented. Theoretical models were applied to IT data, allowing an estimation of the delocalization parameter, α 2, and the electronic coupling parameter, H AB. The results are compared with other valence-trapped binuclear systems.