The synthesis of new dinuclear complexes of the general formula {[Ru-II(trpy)](2)(mu-pdz-dc)(mu-(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 are characterized by the usual analytical and spectroscopic techniques and by X-ray diffraction analysis. Their redox properties are characterized by means of cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Complex 2(+) is used as the starting material to prepare the corresponding Ru-aqua complex {[Ru-II(trpy)(H2O))(2)(mu-pdz-dc)}(2+) (3(2+)), whose electrochemistry is also investigated by means of CV and DPV. Complex 3(2+) is able to catalytically and electrocatalytically oxidize water to dioxygen with moderate efficiencies. In sharp contrast, 3(2+) is a superb catalyst for the epoxidation of alkenes. For the particular case of cis-beta-methylstyrene, the catalyst is capable of carrying out 1320 turnovers with a turnover frequency of 11.0 cycles min(-1), generating cis-beta-methylstyrene oxide stereospecifically.