Treatment of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H)2 (1; Cp* = η5-C 5Me5) with cycloalkene resulted in exclusive formation of the μ3-cycloalkyne complex {Cp*Ru(μ-H)}3(μ3-η2:η2(⊥)-C n H2 n - 4) (2a; n = 5, 2b; n = 6) as a result of vinylic C−H bond cleavage. VT NMR studies revealed fluxional behavior of the perpendicularly coordinated cycloalkyne ligand. Reaction of 2b with carbon monoxide afforded the 48-electron complex (Cp*Ru)3(μ-CO)(μ3-CO)(μ-H)(μ3-η2(∥)-C6H8) (3b) with a parallel-coordinated alkyne ligand.

Treatment of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H)2 (1; Cp* = η5-C5Me5) with substituted alkynes results in the exclusive formation of the μ3-alkyne complex {Cp*Ru(μ-H)}3(μ3-η2:η2(⊥)-RCCR‘) (2a, R = Ph, R‘ = H; 2b, R = C(CH3)3, R‘ = H; 2c, R = Ph, R‘ = CH3), in which the alkyne adopts a perpendicular coordination mode relative to one of the Ru−Ru edges, as revealed by an X-ray structure determination. The acetylenic carbon located inside the trinuclear core is shown to appear at particularly high magnetic field in the 13C NMR spectra.

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