Syntheses and molecular structures of new ferrocenylacetylide-bridged binuclear cobalt carbonyl cluster compounds

The reaction of ferrocenylacetylide compounds with Co₂(CO)₈ at room temperature affords four complexes bearing ferrocenyl units with approximately tetrahedral (μ-alkyne)dicobalt moieties R–(C≡C) _n –R′] Co₂(CO)₆] _{n ′} R?=?C₅H₅FeC₅H₄-C(CH₃)₂-C₅H₄FeC₅H₄, R′?=?H, n?=?1, n′?=?1 (1); R?=?C₅H₅FeC₅H₄ ferrocenyl (Fc)], R′?=?–CH=CHCl, n?=?1, n′?=?1 (2); R?=?Fc, R′?=?Fc, n?=?2, n′?=?1 (3), n′?=?2 (4)]. The compounds were characterized by elemental analysis, IR, ¹H(¹³C) NMR, MS and single-crystal X-ray diffraction analysis. The X-ray analyses show that coordination of the carbon–carbon triple bond and the dicobalt unit result in the formation of a Co₂C₂ tetrahedral core, and the substituents on the acetylenic units show a distortion from linearity that reflects this coordination mode.