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

Abstract

The dinuclear ruthenium complex [Ru₂H(μ-H)(Me₂dad)(dbcot)₂] contains a 1,4-dimethyl-diazabuta-1,3-diene (Me₂dad) as a non-innocent bridging ligand between the metal centers to give a [Ru₂(Me₂dad)] core. In addition, each ruthenium is bound to one dibenzo[a,e]cyclooctatetraene (dbcot) ligand. This Ru dimer converts H₂ to protons and electrons. It also catalyzes reversibly under mild conditions the selective hydrogenation of vitamins K₂ and K₃ to their corresponding hydroquinone equivalents without affecting the CC double bonds. Mechanistic studies suggest that the [Ru₂(Me₂dad)] moiety, like hydrogenases, reacts with H₂ and releases electrons and protons stepwise.