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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.

Molybdenum hexacarbonyl
Stereo, skeletal formula of molybdenum hexacarbonyl
Ball and stick model of molybdenum hexacarbonyl
Sample of molybdenum hexacarbonyl
IUPAC name
Systematic IUPAC name
3D model (JSmol)
ECHA InfoCard 100.034.271
EC Number 237-713-3
3798, 562210
MeSH Hexacarbonylmolybdenum
UN number 3466
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)
0 D
−989.1 kJ mol−1
−2123.4 kJ mol−1
Safety data sheet External MSDS
Very Toxic T+
R-phrases (outdated) R26/27/28
S-phrases (outdated) (S1/2), S36/37/39, S45
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
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


Structure and propertiesEdit

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. By this strict definition, Mo(CO)6 is not organometallic.[citation needed]


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]

Intermediate in inorganic and organometallic synthesisEdit

Mo(CO)6 is a popular reagent in organometallic synthesis[3] because one or more CO ligands can be displaced by other donor 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.

Monosubstituted derivativesEdit

UV-photolysis of a THF solution of Mo(CO)6 gives Mo(CO)5(THF). This complex is useful for the selective preparation of many monosubstituted derivatives.

Disubstituted derivativesEdit

Chelating ligands can be installed by direct reaction with Mo(CO)6. For example, Mo(CO)6 reacts with 2,2′-bipyridine to afford Mo(CO)4(bipy).

In many cases, sources of Mo(CO)4 are sought. For example, the two piperidine ligands in this yellow-colored compound Mo(CO)4(piperidine)2 are labile, which allows other ligands to be introduced under mild conditions. This bis(piperidine) complex is produced by the thermal reaction of Mo(CO)6 with piperidine. Reaction of [Mo(CO)4(piperidine)2] with triphenyl phosphine gives cis-[Mo(CO)4(PPh3)2]. This cis- complex isomerizes in toluene to trans-[Mo(CO)4(PPh3)2].[5] A related disubstituted derivative is (norbornadiene)molybdenum tetracarbonyl.

Trisubstituted derivativesEdit

Upon heating in acetonitrile solution, Mo(CO)6 converts to the tris(acetonitrile) derivative. The compound serves as a source of "Mo(CO)3". It reacts 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 atomsEdit

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 handlingEdit

Like all metal carbonyls, Mo(CO)6 is dangerous source of volatile metal as well as CO. Can be fatal if on skin or swallowed.[8] It diffuses readily into plastic stoppers.


  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.
  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. doi:10.1080/10408430600930438.
  8. ^ [1] Ereztech SDS]

Further readingEdit