Formation of a μ₃‑Acetylide on a Ru₃ Cluster via Coupling of μ‑Methylene with Isocyanide Accompanied by Elimination of Amine: A Model of Hydrogen-Assisted C–C Bond Formation on a Metal Surface

A μ₃-methylidyne complex of ruthenium, [(Cp*Ru)₃(μ₃-CH)­(μ-H)₂(μ₃-S)] (3; Cp* = (C₅Me₅)­Ru), was synthesized by the reaction of [{Cp*Ru­(μ-H)}₃(μ₃-H)₂] (1) with thioanisole. Complex 3 isomerized to a μ-methylene intermediate via reductive C–H bond formation, which could uptake a two-electron donor, E, to yield [(Cp*Ru)₃(μ-CH₂)­(μ-H)­(μ₃-S)­(μ-E)] (4, E = CO; 5, E = t-BuNC). Although the μ-carbonyl complex 4 did not undergo C–C bond formation, thermolysis of 5 resulted in formation of the μ₃-ethynyl complex [(Cp*Ru)₃(μ₃-CCH)­(μ₃-S)] (6), along with elimination of t-BuNH₂. In the presence of CF₃CH₂OH, C–C bond formation proceeded at 25 °C and afforded μ₃-aminovinylidene complex [(Cp*Ru)­{μ₃-η²-C = C­(N^tBuH)­H}­(μ-H)­(μ₃-S)] (7), which was also transformed to 6 upon heating at 80 °C. Although C–C bond formation does not occur in the CO analogue, formation of 6 via the reaction with t-BuNC can be viewed as a model of H-assisted C–C bond formation for Fischer–Tropsch synthesis.