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 Ball and stick model of molybdenum hexacarbonyl
Names
IUPAC name Hexacarbonylmolybdenum(0)
Systematic IUPAC name Hexacarbonylmolybdenum[1]
Identifiers
CAS Number	13939-06-5 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:30508 Y
ChemSpider	21428397 Y
ECHA InfoCard	100.034.271
EC Number	237-713-3
Gmelin Reference	3798, 562210
MeSH	Hexacarbonylmolybdenum
PubChem CID	98885
UN number	3466
CompTox Dashboard (EPA)	DTXSID70894074
InChI InChI=1S/6CO.Mo/c6*1-2; N Key: KMKBZNSIJQWHJA-UHFFFAOYSA-N N
SMILES O=C=[Mo](=C=O)(=C=O)(=C=O)(=C=O)=C=O
Properties
Chemical formula	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)
Solubility in water	insoluble
Solubility	slightly soluble in THF, diglyme, acetonitrile[2]
Structure
Crystal structure	Orthogonal
Coordination geometry	Octahedral
Dipole moment	0 D
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−989.1 kJ mol−1
Std enthalpy of combustion (ΔcH⦵298)	−2123.4 kJ mol−1
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H300, H310, H315, H319, H330, H413
Precautionary statements	P261, P271, P280, P304+P340+P311, P405, P501
NFPA 704 (fire 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 YN ?) 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. hdl:10773/40120. 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

• 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.