A low-valent dinuclear ruthenium diazadiene complex catalyzes the oxidation of dihydrogen and reversible hydrogenation of quinones

The dinuclear ruthenium complex [Ru(2)H(μ-H)(Me(2)dad)(dbcot)(2)] contains a 1,4-dimethyl-diazabuta-1,3-diene (Me(2)dad) as a non-innocent bridging ligand between the metal centers to give a [Ru(2)(Me(2)dad)] core. In addition, each ruthenium is bound to one dibenzo[a,e]cyclooctatetraene (dbcot) ligand. This Ru dimer converts H(2) to protons and electrons. It also catalyzes reversibly under mild conditions the selective hydrogenation of vitamins K(2) and K(3) to their corresponding hydroquinone equivalents without affecting the C[double bond, length as m-dash]C double bonds. Mechanistic studies suggest that the [Ru(2)(Me(2)dad)] moiety, like hydrogenases, reacts with H(2) and releases electrons and protons stepwise.