Dicobalt hexacarbonyl acetylene complexes are a family of In organocobalt compounds with the formula . A large variety of R groups are tolerated. They are red compounds that are soluble in organic solvents. They arise from the reaction of alkynes and dicobalt octacarbonyl:
According to X-ray crystallography, the two Co atoms and two alkyne carbons form the vertices of a distorted tetrahedron. The C-C distance for the bridging alkyne ligand is 1.33 ÃÂ , and the Co-Co distance is 2.47 ÃÂ . The core has C<sub>2v</sub> symmetry. The structure is related to that of methylidynetricobaltnonacarbonyl and tetracobalt dodecacarbonyl, which are also tetrahedranes.
These complexes are intermediates in the Pauson-Khand reaction.