Reaction of the complex cis-[Ru(12S4)(dmso)Cl] + (12S4=1,4,7,10-tetrathiacyclododecane) and 4,4′-bipyridine (bpy) produces the mononuclear complex [Ru(12S4)(bpy)Cl] + (1) when a 1:1 stoichiometry is employed while a 2:1 stoichiometry (Ru/bpy) produces the bpy bridged binuclear complex, [{Ru(12S4)Cl} 2 -μ-(bpy)] 2+ (2). The crystal structures of both complexes show the Ru(II) in a distorted octahedral environment of a cis arrangement formed by the four S donors from the 12S4, a bpy N donor, and a chloride. The 12S4 ligand adopts the same non-C 2 symmetric conformation at all metal centers in both structures. The bridging of the 4,4′-bpy ligand to both Ru(II) centers in (2) is indicated by the presence of two resonances in its 1 H NMR spectrum and three in its 13 C NMR spectrum. The lower symmetry of the mononuclear complex (1) produces more complicated NMR spectra. Cyclic voltammetry for both complexes in CH 3 CN show a reversible one electron oxidation wave with E 1/2 near +670mV vs. Fc/Fc + which is assigned as a Ru(II)/Ru(III) couple.