Fluxional Behavior of a Perpendicularly Coordinated μ3-Alkyne Ligand on a Triruthenium Cluster. Synthesis and Structure of a μ3-η2:η2(⊥)-Cycloalkyne Complex

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.