Reaction of [MoXX′ (CO) 3 (NCMe) 2] with RC2R′ in CH2Cl2 at room temperature gave the bis (alkyne) complexes [MoXX′ (CO) (NCMe) (η2-RC2R′) 2] (X=X′=I, R=R′=Me; X=X′=Br, R=R′=Me, Ph; X′=I, X=Cl, Br, R=R′=Me, Ph) (1→7) in high yield. The molecular structures of [MoI2 (CO) (NCMe) (η2-RC2R) 2] (R=Me, Ph) have been determined by X-ray crystallography. The two structures are very similar, with the two alkyne ligands cis- and parallel to each other and trans- to the two iodo ligands. The carbon monoxide and acetonitrile ligands occupy the two axial sites. Treatment of [MoI2 (CO) (NCMe) (η2-RC2Ph) 2] with an equimolar amount of L∩L {for R=Ph, L∩L=5,6-Me2-1,10-phen, Ph2P (CH2) 2PPh2; for R=Me, L∩L=2,2′-bipy, Ph2P (CH2) nPPh2, n=1, 3, 4} yielded the mono (alkyne) complexes [MoI2 (CO) (L∩L) (η2-RC2Ph) ] (8→13) , which for L∩L=5,6-Me2-1,10-phen, R=Ph (8) was crystallogaphically characterised. The geometry around the molybdenum centre is essentially octahedral, with the phenanthroline ligand trans- to a carbonyl and an iodide ligand, with the alkyne and other iodide group in the axial sites. Reaction of [MoI2 (CO) (NCMe) (η2-MeC2Ph) 2] with two equivalents of NaS2CNMe2 in CH2Cl2 gave [Mo (CO) (S2CNMe2) 2 (η2-MeC2Ph) ] (14) .