Molybdenum hexacarbonyl - Misplaced Pages

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.

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".

Occurrence

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

Inorganic and organometallic research

Molybdenum hexacarbonyl is a popular reagent in academic research.

One or more CO ligands can be displaced by other ligands. Mo(CO)₆, , 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 with triphenyl phosphine in boiling dichloromethane (b.p. ca. 40 °C) gives cis-. This cis- complex isomerizes in toluene to trans-.

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 , whereas treatment with KTp and sodium cyclopentadienide gives and anions, respectively. These anions react with a variety of electrophiles. 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.

Safety and handling

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

References

"Hexacarbonylmolybdenum (CHEBI:30508)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
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.
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)
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.
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.
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.
"THE SYNTHESIS & SPECTROSCOPIC CHARACTERISATION OF METAL CARBONYL COMPLEXES" (PDF). www.chm.bris.ac.uk. Archived from the original (PDF) on March 9, 2008.
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.
Elschenbroich, C.; Salzer, A. (1992). Organometallics: A Concise Introduction (2nd ed.). Weinheim: Wiley-VCH. ISBN 3-527-28165-7.
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.

v t e Molybdenum compounds
Mo(0)	Mo(CO)₆ Mo₃P
Mo(II)	MoBr₂ MoCl₂ MoI₂ MoSi₂
Mo(III)	MoBr₃ MoCl₃ MoI₃ Mo₂O₃ Mo₂(OtBu)₆ MoP
Mo(IV)	MoBr₄ MoCl₄ MoF₄ MoO₂ MoS₂ MoSe₂ MoTe₂ MoP₂ MoAs₂
Mo(V)	MoCl₅ MoF₅ Mo₂O₅
Mo(VI)	Molybdates Molybdic acid MoO₃ MoCl₆ MoOF₄ MoOCl₄ MoF₂O₂ MoO₂Cl₂ MoF₆ MoS₃