Synthesis and Characterization of Triruthenium Complexes Containing a Perpendicularly Coordinated Alkyne Ligand

Abstract

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.

Synthesis, structure, and property of a triruthenium cluster having a μ-alkyl ligand: Transformation of a μ3(⊥)-alkyne ligand into a μ-alkyl ligand via a μ3-vinylidene complex

“…The equilibrium between 1 and 5 was strongly affected by the size of the substituents, and a bulky substituent tilts the equilibrium in favor of the (^)-alkyne form. Although the signals for 5 were not observed in the 1 H NMR spectrum of the equilibrium mixture of 5a and 1a, spin saturation transfer was observed between the methine proton and the hydrido ligands of 1a [9]. This fact indicates that there is a slight contribution of 5a in solution.…”

“…Treatment of the perpendicularly coordinated alkyne complex, {Cp * Ru(l-H)} 3 (l 3 -g 2 :g 2 (^)-PhCCH) (1a) [9], with atmospheric carbon monoxide at 25°C resulted in a quantitative formation of a l-phenethyl complex, (Cp * Ru) 3 (l-g 2 -HCHCH 2 Ph)(l-CO) 2 (l 3 -CO) (2a), having an a-C-H agostic interaction (Eq. (1)).…”

“…CD 2 Cl 2 was dried over diphosphorus pentoxide and stored under an argon atmosphere. l 3 -Alkyne complexes {Cp * Ru(l-H)} 3 (l 3 -g 2 :g 2 (^)-RCCH) (1a; R@Ph, 1b; R = t Bu) were prepared according to a published method [9]. IR spectra were recorded on a Nicolet AVATAR 360 E.S.P.…”

“…Formation of a l 3 -styrylidene complex 5a (66.7% yield) with a l 3 -(^)-phenylacetylene complex 1a (33.3% yield) was observed by means of 1 H NMR spectroscopy. Complex 1a was characterized by comparing the spectra with its authentic [9]. 1 4.11.…”

“…Shapley and co-workers clearly demonstrated rapid equilibrium among l 3 -methylidyne, l 3 -methylene, and l-methyl groups in the ''Os 3 (CO) 9 H n (CH 4Àn )'' (n = 1-3) system on the basis of the isotopic perturbation of resonance (IPR) technique [3,4]. Such transformation of a hydrocarbyl on a cluster is highly related to the activation of hydrocarbons on the cluster, and understanding the mechanistic details of the transformation is important for controlling the reactivity of the hydrocarbyls on the cluster [5].…”