Molybdenum hexacarbonyl
2138622
206000963
2008-04-16T11:56:13Z
134.76.64.126
{{Chembox new
| Name = Molybdenum hexacarbonyl
| ImageFile = Molybdenum-hexacarbonyl-2D.png
| IUPACName = hexacarbonylmolybdenum(0)
| Section1 = {{Chembox Identifiers
| CASNo = 13939-06-5
| SMILES =
}}
| Section2 = {{Chembox Properties
| Formula = C<sub>6</sub>O<sub>6</sub>Mo<sub></sub>
| MolarMass = 264.00 g/mol
| Density = 1.96 g/cm<sup>3</sup> solid
| Solubility = insoluble
| MeltingPt = 150 °C
| BoilingPt = sublimes
}}
| Section3 = {{Chembox Structure
| Coordination = octahedral
| CrystalStruct =
| Dipole = 0 [[Debye|D]]
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS = [http://ptcl.chem.ox.ac.uk/MSDS/HE/hexacarbonylmolybdenum.html External MSDS]
| MainHazards = flammable, CO source
| FlashPt =
| RPhrases = 26/27/28
| SPhrases = 36/37/39-45
}}
| Section8 = {{Chembox Related
| OtherCpds = [[Chromium hexacarbonyl|Cr(CO)<sub>6</sub>]]<br /> [[Iron pentacarbonyl|Fe(CO)<sub>5</sub>]]<br /> [[Dimanganese decacarbonyl|Mn<sub>2</sub>(CO)<sub>10</sub>]]<br /> [[Tungsten hexacarbonyl|W(CO)<sub>6</sub>]]}}
}}
'''Molybdenum hexacarbonyl''' (also called '''molybdenum carbonyl''') is the [[chemical compound]] with the formula Mo(CO)<sub>6</sub>. This colorless solid, like its [[chromium hexacarbonyl|chromium]] and [[tungsten hexacarbonyl|tungsten]] analogues, is noteworthy as a volatile, air-stable derivative of a metal in its zero oxidation state.
==Preparation, properties, and structure==
Mo(CO)<sub>6</sub> is prepared by the [[Redox|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)<sub>6</sub> adopts an [[octahedral geometry]] consisting of six rod-like CO [[ligand]]s 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)<sub>6</sub> is not organometallic.
==Applications in inorganic and organometallic synthesis==
Mo(CO)<sub>6</sub> is a popular reagent in organometallic synthesis<ref>Faller, J. W. "Hexacarbonylmolybdenum" in [[Encyclopedia of Reagents for Organic Synthesis]] (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289}}.</ref> because one or more CO ligands can be displaced by other donor ligands.<ref>http://www.chm.bris.ac.uk/teaching-labs/inorganic2ndyear/2004-2005labmanual/Experiment3.pdf</ref> For example, Mo(CO)<sub>6</sub> reacts with [[2,2'-bipyridine]] to afford Mo(CO)<sub>4</sub>(bipy). UV-photolysis of a [[THF]] solution of Mo(CO)<sub>6</sub> gives Mo(CO)<sub>5</sub>(THF). Many metal carbonyls are similarly photo-activatable.
===[Mo(CO)<sub>4</sub>(piperidine)<sub>2</sub>]===
The thermal reaction of Mo(CO)<sub>6</sub> with [[piperidine]] affords Mo(CO)<sub>4</sub>(piperidine)<sub>2</sub>. 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)<sub>4</sub>(piperidine)<sub>2</sub>] with [[triphenyl phosphine]] in [[boiling]] [[dichloromethane]] (b.p. ca. 40 °C) gives [[cis]]-[Mo(CO)<sub>4</sub>(PPh<sub>3</sub>)<sub>2</sub>], this cis complex [[isomer]]izes in [[toluene]] to [[trans]]-[Mo(CO)<sub>4</sub>(PPh<sub>3</sub>)<sub>2</sub>].
===[Mo(CO)<sub>3</sub>(MeCN)<sub>3</sub>]===
Upon heating in a solution of [[acetonitrile]], Mo(CO)<sub>6</sub> converts to its tris(acetonitrile) derivative. The resulting compound serves as a source of "Mo(CO)<sub>3</sub>". For instance treatment with allyl chloride gives [MoCl(allyl)(CO)<sub>2</sub>(MeCN)<sub>2</sub>], whereas treatment with [[Scorpionate ligand|KTp]] and Na[[cyclopentadienyl]] gives [MoTp(CO)<sub>3</sub>]<sup>-</sup> and [MoCp(CO)<sub>3</sub>]<sup>-</sup> anions. These anions can be reacted with electrophiles to form a wide range of products.<ref>Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7</ref>
==Applications in organic synthesis==
Mo(CO)<sub>6</sub>, [Mo(CO)<sub>3</sub>(MeCN)<sub>3</sub>], and related derivatives are employed as [[catalyst]]s in [[organic synthesis]]. For example, these catalysts can be used for [[alkyne metathesis]] and the [[Pauson–Khand reaction]].
==Occurrence in [[nature]] ==
Mo(CO)<sub>6</sub> has been detected in [[landfill]]s and [[sewage]] plants, the reducing, anaerobic environment being conducive to formation of Mo(CO)<sub>6</sub>.<ref>Feldmann, J. “Determination of Ni(CO)<sub>4</sub>, Fe(CO)<sub>5</sub>, Mo(CO)<sub>6</sub>, and W(CO)<sub>6</sub> 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.</ref>
==Safety and handling==
Like all metal carbonyls, Mo(CO)<sub>6</sub> is dangerous source of volatile metal as well as CO. It diffuses readily into plastic stoppers.
==References==
{{reflist}}
==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.
[[Category:Molybdenum compounds]]
[[Category:Carbonyl complexes]]
[[Category:Inorganic carbon compounds]]