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

Abstract

The dinuclear ruthenium complex [Ru2H(mu-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=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.