Coupling of acetylene molecules on ruthenium clusters, involving cleavage of C–Si bonds in the alkyne and coordination of a phenyl ring of a SiPh3 group

Abstract

The reaction of [Ru₃(CO)₁₂] with the disubstituted acetylene Me₃SiCCSiMe₃ yields several compounds where cleavage of the C–Si bond has occurred thus allowing an easy coupling of carbon fragments to produce allene complexes [Ru₄(CO)₁₂(μ₄-η³-Me₃SiCCCSiMe₃)] (2), differently substituted metallacycle compounds [Ru₃(μ₂-CO)₂(CO)₆{μ₃-C(R)C(SiMe₃)C(R′)C(SiMe₃)}] (3) [R = SiMe₃, R′ = CH₃ (3a); R = H, R′ = CH₃ (3b); R = CCSiMe₃; R′ = H (3c)] and a pentanuclear ruthenium cluster containing three separate alkyne units; two with one SiMe₃ substituent and one with two SiMe₃ substituents, coordinated to the metal framework [Ru₅(CO)₁₂{μ₃-(C₂SiMe₃)₂}μ₂-C₂(SiMe₃)₂] (4). Another product of the reaction is the acetylide derivative [(μ-H)Ru₃(CO)₉(CCSiMe₃)] (1a). In order to determine if this was an intermediate for the formation of the products already mentioned, the reaction of this compound was carried out with the two terminal alkynes HCCSiMe₃ and HCCSiPh₃. In the case of the reaction with the SiMe₃ derivative, products included the same metallocyclopentadiene derivatives as well as the pentanuclear cluster already mentioned. If the acetylene is the SiPh₃ derivative, products show coupling of SiPh₃CC units with CCSiMe₃ fragments and CO molecules, coordinated to mononuclear [Ru(CO)₂(CCSiPh₃){η⁵-(CCSiPh₃)₂C(OH)}] (7), dinuclear [Ru₂(CO)₃{Ph₃Si(H)CC(H)CC(SiMe₃)C(O)C(SiPh₃)C(H)}] (8) and trinuclear [Ru₃(CO)₄{(Ph₃Si(H)CC(H)CC(SiMe₃)}{(H)CC(SiPh₃)C(O)}] (9) clusters. One important characteristic in compounds 8 and 9 is that one of the phenyl rings of the SiPh₃ substituent is η⁶ coordinated to a ruthenium atom. Compounds 2 to 4(a–c) and 7 to 9 were characterized spectroscopically and by X-ray diffraction.