Cyclopentadienylmolybdenum tricarbonyl dimer is the chemical compound with the formula Cp<sub>2</sub>Mo<sub>2</sub>(CO)<sub>6</sub>, where Cp is C<sub>5</sub>H<sub>5</sub>. A dark red solid, it has been the subject of much research although it has no known practical uses.
The molecule exists in two rotamers, gauche and anti. The six CO ligands are terminal and the Mo-Mo bond distance is 3.2325 ÃÂ . The compound is prepared by treatment of molybdenum hexacarbonyl with sodium cyclopentadienide followed by oxidation of the resulting NaMo(CO)<sub>3</sub>(C<sub>5</sub>H<sub>5</sub>). Other methods have been developed starting with Mo(CO)<sub>3</sub>(CH<sub>3</sub>CN)<sub>3</sub> instead of Mo(CO)<sub>6</sub>.
Thermolysis of this compound in hot solution of diglyme (bis(2-methoxyethyl)ether) results in decarbonylation, giving the tetracarbonyl, which has a formal triple bond between the Mo centers (d<sub>MoMo</sub> = 2.448 ÃÂ ):
The resulting cyclopentadienylmolybdenum dicarbonyl dimer in turn binds a variety of substrates across the metal-metal triple bond.