Reactivity of Methyl Diruthenium Complexes with CO and Bipyridine Ligands

Two different methyl diruthenium complexes, [cis-{(η5-C5H3)2(CMe2)2}­Ru2(CO)4(CH3)]­[OTf] and [cis-{(η5-C5H3)2(CMe2)2}­Ru2(κ2-(4,4′-di-tert-butyl)-2,2′-bipyridine)2(μ-CH3)]­[B­(ArF)4], have been synthesized and characterized. When CO is the ancillary ligand, the CH3 group is terminal and susceptible to migration to the Cp ligand. Computationally, this methyl complex has two Ru­(II) centers with a dative bond, and one of the metal centers is reduced by the rate-determining methyl migration to the Cp ligand. When the ancillary ligand is di-tert-butylbipyridine, the CH3 group bridges the two ruthenium centers where one ruthenium has a direct Ru–C bond and the other one interacts with the CH3 group through an agostic interaction. Interchange of the CH3 group between the rutheniums has low activation barriers. Here, addition of an acid, [H­(OEt2)2]­[B­(ArF)4], causes the migration of the CH3 group to the Cp ligand.