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| Molybdenum hexacarbonyl | |
|---|---|
| Chemical name | Molybdenum hexacarbonyl |
| Chemical formula | C6O6Mo |
| Molecular mass | 264.00 g/mol |
| Melting point | 150 °C |
| Boiling point | 156.4 °C |
| Density | 1.96 g/cm3 |
| CAS number | 13939-06-5 |
| SMILES | |
| Mo(CO)6 | |
| Chemical infobox | |
General overview
Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. The compound exists as colorless crystals that sublime at room temperature. Molybdenum hexacarbonyl is able to diffuse into plastic stoppers, if a glass vial containing a little of the solid is sealed with a clear stopper and allowed to stand for several weeks at room temperature then the stopper will darken. This is due to the molybdenum hexacarbonyl diffusing into the plastic before breaking down to form a brown or black solid.
It 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 dissolves 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.
Applications in inorganic and organometallic synthesis
Mo(CO)6 is a popular reagent in organometallic synthesis because one or more CO ligands can be displaced by other donor ligands*. For example, when a toluene solution of Mo(CO)6 and 2,2'-bipyridine (aka bipy) is boiled, one obtains Mo(CO)4(bipy). In addition to this thermal reaction, UV-photolysis of a THF solution of Mo(CO)6 gives Mo(CO)5(THF). Many metal carbonyls are similarly photo-activatable.
*
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 with triphenyl phosphine in boiling dichloromethane (b.p. ca. 40 C) gives cis-isomerised by boiling under reflux in toluene to form trans-[Mo(CO)4(PPh3)2" target="_blank" >*.*
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". or instance treatment with allyl chloride gives while treatment with KTp (potassium tris pyrazoyl hydroboride, an example of a Scorpionate ligand) or NaCp (sodium cyclopentadienate) will form *- anions. These anions can be reacted with electrophiles to form a wide range of products.Applications in organic synthesis
Mo(CO)6, *, 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.
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,** 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.
References
- MSDS http://ptcl.chem.ox.ac.uk *
- 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.
External links
Molybdenum compounds | Carbonyl complexes | Inorganic carbon compounds
"Molybdenum hexacarbonyl"