Molybdenum hexacarbonyl

Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. This colorless solid, like its chromium, tungsten, and seaborgium 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
Stereo, skeletal formula of molybdenum hexacarbonyl
Ball and stick model of molybdenum hexacarbonyl
Ball and stick model of molybdenum hexacarbonyl
Sample of molybdenum hexacarbonyl
Names
IUPAC name
Hexacarbonylmolybdenum(0)
Systematic IUPAC name
Hexacarbonylmolybdenum[1]
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.034.271
EC Number
  • 237-713-3
3798, 562210
MeSH Hexacarbonylmolybdenum
UN number 3466
  • InChI=1S/6CO.Mo/c6*1-2; ☒N
    Key: KMKBZNSIJQWHJA-UHFFFAOYSA-N ☒N
  • O=C=[Mo](=C=O)(=C=O)(=C=O)(=C=O)=C=O
Properties
C6MoO6
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)
insoluble
Solubility slightly soluble in THF, diglyme, acetonitrile[2]
Structure
Orthogonal
Octahedral
0 D
Thermochemistry
−989.1 kJ mol−1
−2123.4 kJ mol−1
Hazards
GHS labelling:
GHS06: Toxic
Danger
H300, H310, H315, H319, H330, H413
P261, P271, P280, P304+P340+P311, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
4
1
0
Safety data sheet (SDS) External MSDS
Related compounds
Related compounds
 Chromium hexacarbonyl


Tungsten hexacarbonyl
Seaborgium hexacarbonyl[3]

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

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.

Like many metal carbonyls, Mo(CO)6 is generally prepared by "reductive carbonylation", which involves reduction of a metal halide with under an atmosphere of carbon monoxide. As described in a 2023 survey of methods "most cost-effective routes for the synthesis of group 6 hexacarbonyls are based on the reduction of the metal chlorides (CrCl3, MoCl5 or WCl6) with magnesium, zinc or aluminium powders... under CO pressures".[4]

Occurrence

Mo(CO)6 has been detected in landfills and sewage plants, the reducing, anaerobic environment being conducive to formation of Mo(CO)6.[5]

Inorganic and organometallic research

Molybdenum hexacarbonyl is a popular reagent in academic research.[6]

One or more CO ligands can be displaced by other ligands.[7] 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).

[Mo(CO)4(piperidine)2]

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].[8]

[Mo(CO)3(MeCN)3]

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.[9] 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.[10]

Safety and handling

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

References
  1. "Hexacarbonylmolybdenum (CHEBI:30508)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
  2. Faller, John W.; Brummond, Kay M.; Mitasev, Branko (15 September 2006). "Hexacarbonylmolybdenum". Encyclopedia of Reagents for Organic Synthesis. Wiley. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780470842898.
  3. Even, J.; Yakushev, A.; Dullmann, C. E.; Haba, H.; Asai, M.; Sato, T. K.; Brand, H.; Di Nitto, A.; Eichler, R.; Fan, F. L.; Hartmann, W.; Huang, M.; Jager, E.; Kaji, D.; Kanaya, J.; Kaneya, Y.; Khuyagbaatar, J.; Kindler, B.; Kratz, J. V.; Krier, J.; Kudou, Y.; Kurz, N.; Lommel, B.; Miyashita, S.; Morimoto, K.; Morita, K.; Murakami, M.; Nagame, Y.; Nitsche, H.; et al. (2014). "Synthesis and detection of a seaborgium carbonyl complex". Science. 345 (6203): 1491–3. Bibcode:2014Sci...345.1491E. doi:10.1126/science.1255720. PMID 25237098. S2CID 206558746. (subscription required)
  4. Bruno, Sofia M.; Valente, Anabela A.; Gonçalves, Isabel S.; Pillinger, Martyn (2023). "Group 6 Carbonyl Complexes of N,O,P-Ligands as Precursors of High-Valent Metal-Oxo Catalysts for Olefin Epoxidation". Coordination Chemistry Reviews. 478: 214983. doi:10.1016/j.ccr.2022.214983. S2CID 255329673.
  5. 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". Journal of Environmental Monitoring. 1 (1): 33–37. doi:10.1039/a807277i. PMID 11529076.
  6. 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.
  7. "THE SYNTHESIS & SPECTROSCOPIC CHARACTERISATION OF METAL CARBONYL COMPLEXES" (PDF). www.chm.bris.ac.uk. Archived from the original (PDF) on March 9, 2008.
  8. 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.
  9. Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7.
  10. 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
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