Molybdenum hexacarbonyl


Molybdenum hexacarbonyl
Stereo, skeletal formula of molybdenum hexacarbonyl
Ball and stick model of molybdenum hexacarbonyl
Sample of molybdenum hexacarbonyl
IUPAC name
Systematic IUPAC name
  • 13939-06-5 checkY
3D model (JSmol)
  • Interactive image
  • CHEBI:30508 checkY
  • 21428397 checkY
ECHA InfoCard 100.034.271 Edit this at Wikidata
EC Number
  • 237-713-3
3798, 562210
MeSH Hexacarbonylmolybdenum
  • 98885
UN number 3466
  • DTXSID70894074 Edit this at Wikidata
  • InChI=1S/6CO.Mo/c6*1-2; ☒N
  • O=C=[Mo](=C=O)(=C=O)(=C=O)(=C=O)=C=O
Molar mass 264.01 g·mol−1
Appearance Vivid, white, translucent crystals
Density 1.96 g cm−3
Melting point 150 °C (302 °F; 423 K)
Boiling point 156 °C (313 °F; 429 K)
Solubility soluble in benzene, paraffin oil
slightly soluble in ether
0 D
−989.1 kJ mol−1
−2123.4 kJ mol−1
GHS labelling:
GHS06: Toxic
H300, H310, H315, H319, H330, H413
P261, P271, P280, P304+P340+P311, P405, P501
NFPA 704 (fire diamond)
Safety data sheet (SDS) External MSDS
Related compounds
Related compounds
Chromium hexacarbonyl

Tungsten hexacarbonyl

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

Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. This colorless solid, like its chromium and tungsten analogues, is noteworthy as a volatile, air-stable derivative of a metal in its zero oxidation state.

Structure and properties

Mo(CO)6 adopts an octahedral geometry consisting of six rod-like CO ligands radiating from the central Mo atom. A recurring minor debate in some chemical circles concerns the definition of an "organometallic" compound. Usually, organometallic indicates the presence of a metal directly bonded via a M–C bond to an organic fragment, which must in turn have a C–H bond.

Mo(CO)6 is prepared by the reduction of molybdenum chlorides or oxides under a pressure of carbon monoxide,[citation needed] although it would be unusual to prepare this inexpensive compound in the laboratory. The compound is somewhat air-stable and sparingly soluble in nonpolar organic solvents.


Mo(CO)6 has been detected in landfills and sewage plants, the reducing, anaerobic environment being conducive to formation of Mo(CO)6.[2]

Inorganic and organometallic research

Molybdenum hexacarbonyl is a popular reagent in academic research.[3]

One or more CO ligands can be displaced by other ligands.[4] Mo(CO)6, [Mo(CO)3(MeCN)3], and related derivatives are employed as catalysts in organic synthesis for example, alkyne metathesis and the Pauson–Khand reaction.

Mo(CO)6 reacts with 2,2′-bipyridine to afford Mo(CO)4(bipy). UV-photolysis of a THF solution of Mo(CO)6 gives Mo(CO)5(THF).


The thermal reaction of Mo(CO)6 with piperidine affords Mo(CO)4(piperidine)2. The two piperidine ligands in this yellow-colored compound are labile, which allows other ligands to be introduced under mild conditions. For instance, the reaction of [Mo(CO)4(piperidine)2] with triphenyl phosphine in boiling dichloromethane (b.p. ca. 40 °C) gives cis-[Mo(CO)4(PPh3)2]. This cis- complex isomerizes in toluene to trans-[Mo(CO)4(PPh3)2].[5]


Mo(CO)6 also can be converted to its tris(acetonitrile) derivative. The compound serves as a source of "Mo(CO)3". For instance treatment with allyl chloride gives [MoCl(allyl)(CO)2(MeCN)2], whereas treatment with KTp and sodium cyclopentadienide gives [MoTp(CO)3] and [MoCp(CO)3] anions, respectively. These anions react with a variety of electrophiles.[6] A related source of Mo(CO)3 is cycloheptatrienemolybdenum tricarbonyl.

Source of Mo atoms

Molybdenum hexacarbonyl is widely used in electron beam-induced deposition technique - it is easily vaporized and decomposed by the electron beam providing a convenient source of molybdenum atoms.[7]

Safety and handling

Like all metal carbonyls, Mo(CO)6 is dangerous source of volatile metal as well as CO.


  1. ^ "Hexacarbonylmolybdenum (CHEBI:30508)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
  2. ^ Feldmann, J. (1999). "Determination of Ni(CO)4, Fe(CO)5, Mo(CO)6, and W(CO)6 in Sewage Gas by Using Cryotrapping Gas Chromatography Inductively Coupled Plasma Mass Spectrometry". J. Environ. Monit. 1 (1): 33–37. doi:10.1039/a807277i. PMID 11529076.
  3. ^ Faller, J. W.; Brummond, K. M.; Mitasev, B. (2006). "Hexacarbonylmolybdenum". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.rh004.pub2. ISBN 0471936235.
  4. ^ Archived March 9, 2008, at the Wayback Machine
  5. ^ Darensbourg, D. J.; Kump, R. L. (1978). "A Convenient Synthesis of cis-Mo(CO)4L2 Derivatives (L = Group 5a Ligand) and a Qualitative Study of Their Thermal Reactivity toward Ligand Dissociation". Inorg. Chem. 17 (9): 2680–2682. doi:10.1021/ic50187a062.
  6. ^ Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7.
  7. ^ Randolph, S. J.; Fowlkes, J. D.; Rack, P. D. (2006). "Focused, Nanoscale Electron-Beam-Induced Deposition and Etching". Critical Reviews of Solid State and Materials Sciences. 31 (3): 55–89. Bibcode:2006CRSSM..31...55R. doi:10.1080/10408430600930438. S2CID 93769658.

Further reading

  • Marradi, M. (2005). "Synlett Spotlight 119: Molybdenum Hexacarbonyl [Mo(CO)6]" (PDF). Synlett. 2005 (7): 1195–1196. doi:10.1055/s-2005-865206.
  • Feldmann, J.; Cullen, W. R. (1997). "Occurrence of Volatile Transition Metal Compounds in Landfill Gas: Synthesis of Molybdenum and Tungsten Carbonyls in the Environment". Environ. Sci. Technol. 31 (7): 2125–2129. Bibcode:1997EnST...31.2125F. doi:10.1021/es960952y.
  • Feldmann, J.; Grümping, R.; Hirner, A. V. (1994). "Determination of Volatile Metal and Metalloid Compounds in Gases from Domestic Waste Deposits with GC/ICP-MS". Fresenius' J. Anal. Chem. 350 (4–5): 228–234. doi:10.1007/BF00322474. S2CID 95405500.