CYCLOPENTADIENYL-RUTHENIUM AND CYCLOPENTADIENYL-OSMIUM CHEMISTRY .39. SYNTHESES OF NOVEL ALKYNYL-RUTHENIUM COMPLEXES - X-RAY STRUCTURES OF 2 FORMS OF (RU(PPH3)2(ETA-C5H5))2(MU-C4) AND OF RU(CCC(O)ME)(PPH3)2(ETA-C5H5)

Reactions between [Ru(thf)(PPh3)2(eta-C5Hs)]+ and lithium acetylides have given further examples of substituted ethynyl-ruthenium complexes that are useful precursors of allenylidene and cumulenylidene derivatives. FroM Li2C4, mono- and bi-nuclear ruthenium complexes were obtained: single-crystal X-ray studies have characterised two rotamers of {Ru(PPh3)2(eta-C5H5)}2(mu-C4), which differ in the relative cis and trans orientations of the RuL(n) groups. Protonation of Ru(C=CC=CH)(PPh3)2(eta-C5H5) afforded the butatrienylidene cation [Ru(C=C=C=CH2)(PPh3)2(eta-C5H5)]+, which reacted readily with atmospheric moisture to give the acetylethynyl complex Ru(CaCC(O)Me)(PPh3)2(eta-C5H5), also fully characterised by an X-ray structural study.