New Dinuclear Ruthenium Complexes: Structure and Oxidative Catalysis

The synthesis of new dinuclear complexes
of the general formula {[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 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 {[RuII(trpy)­(H2O)]2(μ-pdz-dc)}2+ (32+), whose
electrochemistry is also investigated by means of CV and DPV. Complex 32+ is able to catalytically and electrocatalytically
oxidize water to dioxygen with moderate efficiencies. In sharp contrast, 32+ is a superb catalyst for the epoxidation 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.