PROPERTIES OF THE MIXED-VALENCE BINUCLEAR COMPLEX ION, [(NH3)5RUIII-NC-OSII(CN)5]

The mixed-valence ion, [(NH3)5Ru(III)-NC-Os(II)(CN)5]-, was prepared i n solution from [Ru(NH3)5H2O]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-controlle d by the loss of water from the Ru(III) moiety, as in related reaction s with [Fe(CN)6]4- and [Ru(CN)6]4-. The binuclear ion shows a distinct ive intervalence band, associated to charge transfer from Os(II) to Ru (III), at 830 nm (epsilon = 3450 M-1 cm-1), with a noticeable asymmetr y, probably associated to spin-orbit coupling. Shifts in the redox pot entials at the metal centers on dimer formation are consistent with th e Os(II)-Ru(III) formulation. By measuring solution Raman spectra in p ost-resonance conditions with respect to the IT band, activation of th e 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 pro blem. IR and Raman results of the solid samples are also presented. Th eoretical models were applied to IT data, allowing an estimation of th e delocalization parameter, alpha2, and the electronic coupling parame ter, H(AB). The results are compared with other valence-trapped binucl ear systems.