Synthesis and Characterization of Triruthenium Complexes Containing a Perpendicularly 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.