When acetylene gas was bubbled through methanol solutions containing the mixed-chalcogenide compounds (CO) 6 Fe 2 (μ-EE') (E ≠E'; E, E' = S, Se, Te), the acetylene adducts (CO) 6 Fe 2 {μ-EC(H)=C(H)E'} (1, 52%, E, E' = S, Se; 2, 46%, E, E' = S, Te; 3, 38%, E, E' = Se, Te) were obtained. In addition, trace amounts of the homochalcogenide derivatives (CO) 6 Fe 2 {μ-EC(H)=C(H)E} (E = S, Se, Te) were also obtained. The Te 2 compound (CO) 6 Fe 2 {μ-TeC(H)=C(H)Te} (4) was obtained in 32% yield from the reaction of (CO) 6 Fe 2 (μ-Te 2 ) with acetylene. Compounds 1-4 were characterized by IR and 1 H, 13 C, 77 Se, and 125 Te NMR spectroscopy. Crystallographic analysis of the phenylacetylene adducts (CO) 6 Fe 2 {μ-SC(Ph)C(H)Se} (5) and (CO) 6 Fe 2 {μ-SC(H)=C(Ph)Te} (6) were carried out. The structures of both 5 and 6 can be described as Fe 2 SE (E = Se, Te) tetrahedral butterfly cores containing the phenylacetylene as a bridge between the two wingtip chalcogen atoms, with three terminally bonded carbonyl groups on each Fe atom.