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.

The reaction of [Ru3(CO)12] with the disubstituted acetylene Me3SiC≡CSiMe3 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-η(3)-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 = C≡CSiMe3; 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){η(5)-(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 η(6) coordinated to a ruthenium atom. Compounds 2 to 4(a-c) and 7 to 9 were characterized spectroscopically and by X-ray diffraction.