Molybdenum hexacarbonyl
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| Molybdenum hexacarbonyl | |
|---|---|
| Chemical name | Molybdenum hexacarbonyl |
| Chemical formula | C6O6Mo |
| Molecular mass | 264.00 g/mol |
| CAS number | 13939-06-5 |
| SMILES | |
| Properties | |
| Density and phase | 1.96 g/cm3 solid |
| Solubility in water | insoluble |
| Other solvents | sparingly in THF |
| Melting point | 150 °C |
| Boiling point | 156.4 °C |
| Structure | |
| Coordination geometry |
octahedral |
| Crystal structure | ? |
| Dipole moment | 0 D |
| Hazards | |
| MSDS | External MSDS |
| Main hazards | flammable, CO source |
| NFPA 704 | |
| Flash point | ? °C |
| R/S statement | R: 26/27/28 S: 36/37/39-45 |
| RTECS number | ? |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| 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 |
|
Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. This colorless compound, like its chromium and tungsten analogues, is noteworthy as a volatile, air-stable derivative of molybdenum 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, but it would be rare to make this inexpensive compound in the laboratory. The compound is somewhat air-stable. It is 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[1]. For example, when a toluene solution of Mo(CO)6 and 2,2'-bipyridine (aka bipy) is boiled, one obtains 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 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], while treatment with KTp andNacyclopentadienyl gives [MoTp(CO)3]- and [MoCp(CO)3]- anions. These anions can be reacted with electrophiles to form a wide range of products.[2]
[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, being a derivative of Mo metal, is not stable on a geological timescale. Surprisingly, Mo(CO)6 has been detected in landfills by the Aberdeen chemist Feldmann,[2][3] he has been responsible for the detection of other transition metal and main group organometallics in the gases coming from sewage plants and landfills. The reducing, anaerobic environment is compatible with Mo(CO)6.
[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.
- ^ Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7
[edit] Other reading
- MSDS http://ptcl.chem.ox.ac.uk [4]
- Synlett spotlight 119
- 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.
