Reversible Transformation of a μ₃‑η³‑C₃ Ring into μ₃‑η²‑Ethyne and μ‑Vinylidene Ligands at a Triruthenium Site upon Deprotonation and Protonation

A μ-vinylidene-μ3-η2-ethyne complex, [(Cp*Ru)3(μ3-CH)­(μ-CCH2)­(μ3-η2-HCCH)] (4; Cp* = η5-C5Me5), was synthesized by the reaction of [(Cp*Ru)3(μ3-CH)­(μ3-η3-C3MeH2−)]+ (3a) with KN­(SiMe3)2 via deprotonation of the methyl group on the μ3-η3-C3 ring followed by C–C bond cleavage. The reaction of 4 with an electrophile resulted in the reconstruction of the μ3-η3-C3 ring via the coupling of two hydrocarbyl moieties at the Ru3 site. The reaction of 4 with iodomethane resulted in C–C bond formation at the β-carbon atom of the vinylidene ligand, leading to the formation of [(Cp*Ru)3(μ3-CH)­(μ3-η3-C3EtH2−)]+ (3c). These unprecedented skeletal rearrangements arose from the unique electronic properties of the μ3-η3-C3 ring, which comprised three unsaturated μ-carbenes.一种μ-亚乙烯基-μ₃-η²-乙炔基配合物（μ-vinylidene-μ₃-η²-ethyne complex），即[(Cp*Ru)₃(μ₃-CH)(μ-C=CH₂)(μ₃-η²-HCCH)]（化合物4；其中Cp*为η⁵-五甲基环戊二烯基（Cp*, η⁵-C₅Me₅）），可通过[(Cp*Ru)₃(μ₃-CH)(μ₃-η³-C₃MeH₂⁻)]⁺（化合物3a）与六甲基二硅基氨基钾（KN(SiMe₃)₂）反应制备得到，该反应经由μ₃-η³-三碳环（μ₃-η³-C₃ ring）上甲基的去质子化（deprotonation）与后续碳-碳键断裂（C–C bond cleavage）两步完成。 化合物4与亲电试剂（electrophile）的反应可通过Ru₃位点上两个烃基片段（hydrocarbyl moieties）的偶联，实现μ₃-η³-三碳环的重构。 化合物4与碘甲烷（iodomethane）的反应则会在亚乙烯基配体（vinylidene ligand）的β-碳原子（β-carbon atom）处形成碳-碳键，最终得到[(Cp*Ru)₃(μ₃-CH)(μ₃-η³-C₃EtH₂⁻)]⁺（化合物3c）。 这类前所未有的骨架重排（skeletal rearrangements）现象，源于由三个不饱和μ-卡宾（μ-carbenes）构成的μ₃-η³-三碳环所具备的独特电子性质。