Molybdenum hexacarbonyl
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| Molybdenum hexacarbonyl | |
|---|---|
 |
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| IUPAC name | hexacarbonylmolybdenum(0) |
| Identifiers | |
| CAS number | [13939-06-5] |
| Properties | |
| Molecular formula | C6O6Mo |
| Molar mass | 264.00 g/mol |
| Density | 1.96 g/cm3 solid |
| Melting point |
150 °C |
| Boiling point |
sublimes |
| Solubility in water | insoluble |
| Structure | |
| Coordination geometry |
octahedral |
| Dipole moment | 0 D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | flammable, CO source |
| R-phrases | 26/27/28 |
| S-phrases | 36/37/39-45 |
| Related compounds | |
| Related compounds | Cr(CO)6 Fe(CO)5 Mn2(CO)10 W(CO)6 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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.
Contents |
[edit] Preparation, properties, and structure
Mo(CO)6 is prepared by the reduction of molybdenum chlorides or oxides under a pressure of carbon monoxide, 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 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 a C-H bond. By this strict definition, Mo(CO)6 is not organometallic.
[edit] Applications in inorganic and organometallic synthesis
Mo(CO)6 is a popular reagent in organometallic synthesis[1] because one or more CO ligands can be displaced by other donor ligands.[2] For example, 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). Many metal carbonyls are similarly photo-activatable.
[edit] [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].
[edit] [Mo(CO)3(MeCN)3]
Upon heating in a solution of acetonitrile, Mo(CO)6 converts to its tris(acetonitrile) derivative. The resulting 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 Nacyclopentadienyl gives [MoTp(CO)3]- and [MoCp(CO)3]- anions. These anions can be reacted with electrophiles to form a wide range of products.[3]
[edit] Applications in organic synthesis
Mo(CO)6, [Mo(CO)3(MeCN)3], and related derivatives are employed as catalysts in organic synthesis. For example, these catalysts can be used for alkyne metathesis and the Pauson–Khand reaction.
[edit] Occurrence in nature
Mo(CO)6 has been detected in landfills and sewage plants, the reducing, anaerobic environment being conducive to formation of Mo(CO)6.[4]
[edit] Safety and handling
Like all metal carbonyls, Mo(CO)6 is dangerous source of volatile metal as well as CO. It diffuses readily into plastic stoppers.
[edit] References
- ^ Faller, J. W. "Hexacarbonylmolybdenum" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.
- ^ http://www.chm.bris.ac.uk/teaching-labs/inorganic2ndyear/2004-2005labmanual/Experiment3.pdf
- ^ Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7
- ^ Feldmann, J. “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, 1999, 1, page 33-37. DOI: 10.1039/a807277i.
[edit] Other reading
- Marradi, "Synlett spotlight 119", SYNLETT 2005, No. 7, pp 1195-1196 doi:10.1055/s-2005-865206
- J. Feldmann, W.R. Cullen, Occurrence of volatile transition metal compounds in landfill gas: synthesis of molybdenum and tungsten carbonyls in the environment, Environ. Sci. Technol. 1997, 31, 2125-2129.
- J. Feldmann, 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. Environm. Mon., 1999, 1, 33-37.
- J. Feldmann, R. Grümping, A.V. Hirner, Determination of volatile metal and metalloid compounds in gases from domestic waste deposits with GC-ICP-MS, Fresenius J. Anal. Chem., 1994, 350, 228-235.
