Deoxygenative Reduction of Diruthenium Carbonyl Complexes (η5-C5H4R)2Ru2(μ-CO)2(CO)2 with Hydrosilanes Leading to Bridging Methylene Complexes (η5-C5H4R)2Ru2(μ-CH2) n (μ-CO)2-n (CO)2 (n = 1, 2; R = H, CH3)

Reaction of diruthenium carbonyl complexes (η5-C5H4R)2Ru2(μ-CO)2(CO)2 (1) with di- or trihydrosilane H n SiR‘4-n (n = 2, 3) at 150 °C results in sequential formation of the mono- (η5-C5H4R)2Ru2(μ-CH2)(μ-CO)(CO)2 (2) and di-μ-methylene complexes (η5-C5H4R)2Ru2(μ-CH2)2(CO)2 (3). Labeling experiments confirm that the C and H atoms in the resulting μ-CH2 moieties come from CO attached to Ru and Hn SiR‘4-n , respectively, and that neither intermolecular CH2 transfer nor H transfer between bridging ligands is involved in the present methylenation. The reduction mechanism of bridging carbonyl ligands has been assumed to be deoxygenative hydrosilation (a direct thermal reaction or a catalytic reaction effected by a ruthenium species present in a reaction mixture). Thus, the present system serves as a model system for formation of a bridging methylene species following Fischer−Tropsch mechanism. The molecular structures of the cis- and trans-isomers of 3a (R = H) have been determined by X-ray crystallography.