Cyclopentadienylmolybdenum tricarbonyl dimer

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Cyclopentadienylmolybdenum tricarbonyl dimer
IUPAC names
Other names
cyclopentadienyl molybdenum carbonyl dimer
12091-64-4 YesY
Molar mass 489.96 g/mol
Appearance dark red crystalline solid
Melting point 222 °C (432 °F; 495 K)
Boiling point dec.
0.112 D
Main hazards flammable
R-phrases 20/21/22
S-phrases 36
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Cyclopentadienylmolybdenum tricarbonyl dimer is the chemical compound with the formula Cp2Mo2(CO)6, where Cp is C5H5. This a dark red crystalline solid is air stable in solid form, but decomposes in solution when exposed to air. It is one of the most important and most accessible organomolybdenum compounds, although it has no practical uses.

Structure and synthesis[edit]

The molecule exists in two rotamers, gauche and anti.[1] The six CO ligands are terminal and the Mo-Mo bond distance is 3.2325 Å.[2] 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.[3] In the first step Mo(CO)6 is converted in hot CH3CN to the air-sensitive Mo(CO)3(CH3CN)3.

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


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 (dMoMo = 2.448 Å):[4]

(C5H5)2Mo2(CO)6 → (C5H5)2Mo2(CO)4 + 2 CO

The resulting cyclopentadienylmolybdenum dicarbonyl dimer in turn binds a variety of substrates across the metal-metal triple bond.


  1. ^ Brian Mann (1997-01-06). "Fluxionality of Cp2Mo2(CO)6". University of Sheffield. 
  2. ^ R. D. Adams, D. M. Collins, and F. A. Cotton (1974). "Molecular Structures and Barriers to Internal Rotation in Bis(η5 -cyclopentadienyl)hexacarbonylditungsten and Its Molybdenum Analog". Inorg. Chem. 13 (5): 1086–1090. doi:10.1021/ic50135a015. 
  3. ^ M. David Curtis, Michael S. Hay (1990). "Cyclopentadienyl Metal Carbonyl Dimers of Molybdenum and Tungsten". Inorganic Syntheses (New York: J. Wiley & Sons) 28: 150–152. doi:10.1002/9780470132593.ch40. ISBN 978-0-471-52619-3. 
  4. ^ Cotton, F. A.; Walton, R. A. “Multiple Bonds Between Metal Atoms” Oxford (Oxford): 1993, p 564ff. ISBN 0-19-855649-7.