Cyclopentadienylmolybdenum tricarbonyl dimer

Cyclopentadienylmolybdenum tricarbonyl dimer is the chemical compound with the formula Cp2Mo2(CO)6, where Cp is C5H5. The compound under normal conditions is a dark red crystalline solid. It is air stable in solid form, but decomposes in solution when exposed to air. It undergoes thermal decarboxylation to the related Cyclopentadienylmolybdenum dicarbonyl dimer. This is of interest in preparative chemistry because of the broad reactivity of the metal-metal triple bond.

Structure and synthesis
The compound is prepared by treatment of Mo(CO)6 in hot dicyclopentadiene. A high-yield route to the dimer involves a two-step, one-pot synthesis. In the first step Mo(CO)6 reacts with refluxing CH3CN under an atmosphere of nitrogen. The resulting Mo(CO)3(CH3CN)3 is quite air-sensitive.
 * Mo(CO)6 +  3 CH3CN  →  Mo(CO)3(CH3CN)3  +  3 CO
 * 2 Mo(CO)3(CH3CN)3 +  2 C5H6  →  (C5H5)2Mo2(CO)6 + H2  +  6 CH3CN

Reactions
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:
 * (C5H5)2Mo2(CO)6 →  (C5H5)2Mo2(CO)4 +  2 CO