Molybdenum(V) chloride
4753858
206690692
2008-04-19T14:04:48Z
AlphaEta
2368277
image redlinked
{{Chembox new
| Name = Molybdenum(V) chloride
| ImageFile = <!-- Molybdenum(V) chloride.jpg -->
<!-- | ImageSize = 200px -->
| ImageName = Molybdenum(V) chloride
| IUPACName = Molybdenum(V) chloride
| OtherNames = Molybdenum pentachloride
| Section1 = {{Chembox Identifiers
| SMILES =
| CASNo = 10241-05-1
| RTECS = QA4690000
}}
| Section2 = {{Chembox Properties
| Formula = MoCl<sub>5</sub>
| MolarMass = 273.21 g/mol
| Appearance = dark-green<br />moisture sensitive
| Density = 2.928 g/cm<sup>3</sup>
| Solubility = hydrolyzes
| Solvent = other solvents
| SolubleOther = chlorocarbons<br />benzene
| MeltingPt = 194 °C
| BoilingPt = 268 °C
}}
| Section3 = {{Chembox Structure
| Coordination = edge-shared bioctahedron
| CrystalStruct =
| Dipole =
}}
| Section7 = {{Chembox Hazards
| ExternalMSDS =
| MainHazards = oxidizer, hydrolyzes to release HCl
| RPhrases = 29-34
| SPhrases = 26-36/37/39-43-45
}}
| Section8 = {{Chembox Related
| OtherCpds = [[titanium tetrachloride]]<br /> [[chromyl chloride]]
}}
}}
'''Molybdenum pentachloride''' is the chemical compound with the formula MoCl<sub>5</sub>. This dark volatile solid is an important starting reagent in the preparation of molybdenum compounds. In the solid state molybdenum pentachloride exists as a dimer with the formula Mo<sub>2</sub>Cl<sub>10</sub>, with a structure similar to that of the corresponding Nb and Ta pentachlorides. In the gas phase, it is a monomeric pentahalide. It is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is 5+, leaving one valence electron.
==Preparation and properties==
MoCl<sub>5</sub> is prepared by chlorination of Mo metal but also chlorination of MoO<sub>3</sub>. Notice that MoCl<sub>6</sub> ''cannot'' be prepared under normal conditions. In contrast, the heavier analogues WCl<sub>6</sub> is well known.
MoCl<sub>5</sub> is a strong oxidant, as indicated by its non-reactivity toward Cl<sub>2</sub>. It is easily reduced by even MeCN to afford the adduct MoCl<sub>4</sub>(MeCN)<sub>2</sub>, which in turn reacts with [[THF]] to give MoCl<sub>4</sub>(THF)<sub>2</sub>, a very versatile reagent in the chemistry of molybdenum. MoCl<sub>5</sub> is reduced by HBr to form MoBr<sub>4</sub>. The reaction is conducted in ethylbromide at -50 C:
:: 2 MCl<sub>5</sub> + 10 HBr → 2 MoBr<sub>4</sub> + 10 HCl + Br<sub>2</sub>
MoBr<sub>4</sub> reacts with THF to give the Mo(III) species mer-MoBr<sub>3</sub>(THF)<sub>3</sub>.
MoCl<sub>5</sub> is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form [MoCl<sub>6</sub>]<sup>-</sup>.
==Safety considerations==
MoCl<sub>5</sub> is an aggressive oxidant and readily hydrolyzes to release HCl.
==References==
{{Citationstyle|date=September 2007}}
{{reflist}}
*T. Kauffmann, S. Torii, T. Inokuchi “Molybdenum(V) Chloride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289.
*Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
* Dilworth, J. R.; Richards, R. L. "The Synthesis of Molybdenum and Tungsten Dinitrogen Compounds" Inorganic Syntheses, 1990, volume 28, pages 33-45. ISBN 0-471-52619-3
*Calderazzo, F.; Maichle-Mossmer, C.; Pampaloni, G. and Strähle, J., "Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange", Journal of the Chemical Society, Dalton Transactions, 1993, pages 655-8.
[[Category:Molybdenum compounds]]
[[Category:Chlorides]]
[[Category:Metal halides]]