Monoacetylide RuCl(C≡CR)P 4 complexes (R=Ph, 4-MeC 6 H 4 , 1,4-C 6 H 4 C≡CH, SiMe 3 , Bu t or COOMe; P=P(OEt) 3 or P(OMe) 3 ) were prepared by allowing RuCl 2 P 4 to react with terminal alkynes RC≡CH in the presence of an excess of NEt 3 . Dinuclear compounds [{Ru[P(OEt) 3 ] 5 } 2 (μ-1,4-C≡CC 6 H 4 C≡C)]Y 2 (Y=PF 6 or BPh 4 ) were also prepared from the reaction of RuCl 2 P 4 with 1,4-HC≡CC 6 H 4 C≡CH. Treatment of RuCl 2 P 4 with Li + [1,4-HC≡CC 6 H 4 C≡C] - afforded bis(alkynyl) Ru(1,4-C≡CC 6 H 4 C≡CH) 2 P 4 [P=P(OEt) 3 , P(OMe) 3 or PPh(OEt) 2 ] derivatives. Protonation reactions of monoacetylides RuCl(C≡CR)P 4 with CF 3 SO 3 H led to vinylidene [RuCl{ C C(H)R}P 4 ]CF 3 SO 3 [R=Ph, 4-MeC 6 H 4 or 1,4-C 6 H 4 C≡CH; P=P(OEt) 3 or P(OMe) 3 ] complexes, which were fully characterised by IR and 1 H-, 3 1 P- and 1 3 C-NMR spectra.