The synthesis of new dinuclear complexes {[RuII(trpy)]2(μ-pdz-dc)(μ-L)}+ [pdz-dc is the pyridazine-3,6-dicarboxylate dianion; trpy is 2,2′:6′,2”-terpyridine; L = Cl (1+) or OH (2+)] is described. These complexes were characterized by the usual anal. and spectroscopic techniques and by x-ray diffraction anal. Their redox properties were characterized by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Complex 2+ was used as the starting material to prep. the corresponding Ru-aqua complex {[RuII(trpy)(H2O)]2(μ-pdz-dc)}2+ (32+), whose electrochem. is also studied by CV and DPV. Complex 32+ is able to catalytically and electrocatalytically oxidize H2O to dioxygen with moderate efficiencies. In sharp contrast, 32+ is a superb catalyst for the epoxidn. of alkenes. For the particular case of cis-β-methylstyrene, the catalyst is capable of carrying out 1320 turnovers with a turnover frequency of 11.0 cycles min-1, generating cis-β-methylstyrene oxide stereospecifically.