Reactions between [Ru(thf)(PPh 3) 2(η-C 5H 5)] + and lithium acetylides have given further examples of substituted ethynylruthenium complexes that are useful precursors of allenylidene and cumulenylidene derivatives. From Li 2C 4, mono- and bi-nuclear ruthenium complexes were obtained: single-crystal X-ray studies have characterised two rotamers of {Ru(PPh 3) 2(η-C 5H 5)} 2(μ-C 4), which differ in the relative cis and trans orientations of the RuL n groups. Protonation of Ru(CCCCH)(PPh 3) 2(η-C 5H 5) afforded the butatrienylidene cation [Ru(CCCCH 2)(PPh 3) 2(η-C 5H 5)] +, which reacted readily with atmospheric moisture to give the acetylethynyl complex Ru{CCC(O)Me}(PPh 3) 2(η-C 5H 5), also fully characterised by an X-ray structural study.