The preparation, characterisation and single-crystal XRD molecular structure determinations of four complexes containing –CC–MLn end-groups, namely Ru{C≡CFc′(I)}(dppe)Cp (1), the vinylidene [Os(=C=CH₂)(PPh₃)₂Cp]PF₆ (2), trans-Pt(C≡CC₆H₄-4-C≡CPh){C≡CC₆H₄-4-C₂Ph[Co₂(μ-dppm)(CO)₄]}(PPh₃)₂ (3), and C₆H₄{μ₃-C₂[AuRu₃(CO)₉(PPh₃)]}₂-1,4 (4) are reported. In these compounds a range of –CC– environments is found, extending from the σ-bonded alkynyl group in 1 to examples where the C₂ unit interacts with either a proton (in vinylidene 2), by bridging a dicobalt carbonyl moiety (in 3) or the AuRu₃ cluster in 4. Changes in geometry are rationalised by considering the various bonding modes.