Molybdenum hexacarbonyl
Chemical compound
From Wikipedia, the free encyclopedia
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.
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| Names | |||
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| IUPAC name
Hexacarbonylmolybdenum(0) | |||
| Systematic IUPAC name
Hexacarbonylmolybdenum[1] | |||
| Identifiers | |||
3D model (JSmol) |
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| ChEBI | |||
| ChemSpider | |||
| ECHA InfoCard | 100.034.271 | ||
| EC Number |
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| 3798, 562210 | |||
| MeSH | Hexacarbonylmolybdenum | ||
PubChem CID |
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| UN number | 3466 | ||
CompTox Dashboard (EPA) |
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| 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 | |||
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: | |||
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| Danger | |||
| 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 | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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
Inorganic and organometallic derivatives
Molybdenum hexacarbonyl is a popular reagent in research.[6] One or more CO ligands can be displaced by other ligands.[7] Examples:
- Mo(CO)6 + bipy → Mo(CO)4(bipy) + 2 CO (bipy = 2,2′-bipyridine)
- Mo(CO)6 + thf → Mo(CO)5(thf) + CO (thf = tetrahydrofuran), this reaction requires UV radiation
Mo(CO)6 + 2 pip → Mo(CO)4(pip)2 + 2 CO (pip = piperidine) Mo(CO)6 + 3 MeCN → Mo(CO)3(MeCN)3 + 3 CO (MeCN = acetonitrile)
Some of these species are suited for substitution. For instance, the reaction of [Mo(CO)4(piperidine)2] with triphenyl phosphine gives cis- and trans-[Mo(CO)4(PPh3)2].[8] [Mo(CO)3(MeCN)3 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.
Organic synthesis
Mo(CO)6, [Mo(CO)3(MeCN)3], and related derivatives are employed as catalysts or reagents in organic synthesis for example, alkyne metathesis and the Pauson–Khand reaction. The hexacarbonyl can serve as a source of CO.[10]
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.[11]
Safety and handling
Like all metal carbonyls, Mo(CO)6 is a dangerous source of volatile metal as well as CO.