Transformation of a μ3‑Benzyne Ligand into Phenol on a Cationic Triruthenium Cluster Supported by a μ3‑Sulfido Ligand

A triruthenium complex containing μ3-η2(||)-benzyne and μ3-sulfido ligands, [(Cp*Ru)3(μ3-S)­{μ3-η2(||)-C6H4}­(μ-H)] (2), was synthesized by the reaction of [(Cp*Ru)3(μ3-S)­(μ-H)3] (1) with benzene. Although 2 was stable toward oxygen and water, two-electron oxidation of 2 with a Ag­(I) salt in the presence of water afforded the dicationic μ-hydroxo complex [(Cp*Ru)3(μ3-S)­{μ3-η2(||)-C6H4}­(μ-OH)]2+ (3). Treatment of 3 with amine resulted in the deprotonation of the μ-hydroxo ligand, and an unsaturated monocationic complex, [(Cp*Ru)3(μ3-S)­(μ3-OC6H4-κO,κC)]+ (4), which possesses a μ3-cyclohexadienonediyl ligand, was formed via reductive C–O bond formation between the μ3-benzyne and transient μ-oxo ligands. Phenol was extruded from the Ru3 cluster upon the hydrogenation of 4 via the formation of a μ3-phenoxo complex, [(Cp*Ru)3(μ3-S)­{μ3-OPh}­(μ-H)]+ (5). The cyclic voltammogram of 2 shows two reversible one-electron redox waves, and a dicationic μ3-benzyne complex, [(Cp*Ru)3(μ3-S)­{μ3-η2:η2(⊥)-C6H4}­(μ-H)]2+(8), was shown to be responsible for the uptake of water to yield μ-hydroxo complex 3.