dicobalt hexacarbonyl acetylene complex

File:Co2(C2Me2)(CO)6.svg.]]

Dicobalt hexacarbonyl acetylene complexes are a family of In organocobalt compounds with the formula {{chem2|Co2(C2R2)(CO)6}}. 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:{{cite journal |doi=10.1021/ja01582a036|title=Acetylenic Dicobalt Hexacarbonyls. Organometallic Compounds Derived from Alkynes and Dicobalt Octacarbonyl1,2 |year=1956 |last1=Greenfield |first1=Harold |last2=Sternberg |first2=Heinz W. |last3=Friedel |first3=Robert A. |last4=Wotiz |first4=John H. |last5=Markby |first5=Raymond |last6=Wender |first6=Irving |journal=Journal of the American Chemical Society |volume=78 |pages=120–124}}

:{{chem2|Co2(CO)8 + R2C2 -> (R2C2)Co2(CO)6 + 2 CO}}

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 Å, and the Co-Co distance is 2.47 Å. The {{chem2| (R2C2)Co2(CO)6}} core has C_2v symmetry.{{cite journal |doi=10.1021/om00161a029|title=Diastereoselective Ligand and Vertex Substitutions in Bimetallic Bridged Alkyne Clusters: X-Ray Crystal Structure of .mu.2-(endo-2-Propynylborneol)hexacarbonyldicobalt |year=1990 |last1=d'Agostino |first1=Michael F. |last2=Frampton |first2=Christopher S. |last3=McGlinchey |first3=Michael J. |journal=Organometallics |volume=9 |issue=11 |pages=2972–2984 }} The structure is related to that of methylidynetricobaltnonacarbonyl and tetracobalt dodecacarbonyl, which are also tetrahedranes.

These complexes are intermediates in the Pauson-Khand reaction.