Reaction of [Ru(bipy),CI,] (bipy = 2,2'-bipyridine) with NaOMe or KOH in methanol at reflux afforded high yields of the dinuclear complex [(R~(bipy),},(p-OMe)~][PF~], 1. Reaction of 1 with NaOEt in ethanol resulted in exchange of the bridge to give [{Ru(bipy),),(p-OEt),][PF,], 2. The crystal structures of 1 and 2showed that the complex cations have similar structures in which two Ru(bipy),,+ fragments, which for steric reasons have the same absolute configuration, are linked by two alkoxide bridges. Each dinuclear complex cation is therefore chiral, and there are equal numbers of each enantiomer in the crystals of both 1 and 2. Electrochemical measurements showed that there is a strong electrochemical interaction between the metal centres, with separations of 0.55 and 0.57 V respectively between the two RU"-RU'" couples corresponding to K , values of 3 x lo9 and 6 x lo9 for the mixed-valence states of 1 and 2. A spectroelectrochemical study of complex 1 showed that oxidation of the mixed-valence state results in a new transition in the electronic spectrum at ca. 1800 nm with E = 5000 dm3 mol-' cm-', which disappears on further oxidation to the Ru"' state. The observations that this transition is not solvatochromic, and that the half-width of the peak is much narrower than the value predicted by Hush theory for vectorial intervalence charge-transfer bands, both point to a class 111 (fully delocalised) mixed-valence state; delocalisation between the d, orbitals of the two metal centres is facilitated by good overlap with oxygen p, orbitals in the Ru,O, core. The magnitude of the electronic interaction V,, is estimated to be 2800 cm-', similar in magnitude to that of the Creutz-Taube ion.
