Preparation and Properties of Diruthenium Hydrido Complexes Having a Bridging Benzoquinone Ligand: Formation of an Alcohol Adduct of a μ-η²:η²-Benzoquinone Complex through Hydrogen Bonding

Diruthenium hydrido complexes containing a bridging 1,4-benzoquinone ligand, {Cp*Ru(μ-H)}2(μ-η2:η2-C6H3RO2) (2a, R = H; 2b, R = Me, Cp* = η5-C5Me5), were synthesized by the reaction of a diruthenium tetrahydrido complex, Cp*Ru(μ-H)4RuCp* (1), with 1,4-benzoquinone and 2-methyl-1,4-benzoquinone. Spectroscopic data unambiguously indicated that the hydrogen bond between the quinonoid oxygen atoms of 2 and alcohol molecules changed the electronic nature of the metal center such that it was significantly different from that in aprotic solvent. Therefore, the rate of the reaction of 2a with acetylene, which afforded a μ-η2-vinyl-μ-η2:η2-benzoquinone complex, (Cp*Ru)2(μ-H)(μ-η2-CHCH2)(μ-η2:η2-C6H4O2) (3), in methanol was 3 times the rate of reaction in benzene.