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Molybdenum(V) chloride

Molybdenum(V) chloride

General
Systematic name	Molybdenum(V) chloride
Other names	Molybdenum pentachloride
Molecular formula	MoCl₅
SMILES	?
Molar mass	273.21 g/mol
Appearance	dark-green moisture sensitive
CAS number	[10241-05-1]
Properties
Density and phase	2.928 g/cm³
Solubility in water	hydrolyzes
Other solvents	chlorocarbons benzene
Melting point	194 °C
Boiling point	268 °C
Structure
Coordination geometry	edge-shared bioctahedron
Crystal structure	?
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	oxidizer, hydrolyzes to release HCl
NFPA 704
R/S statement	R: 29-34 S: 26-36/37/39-43-45
RTECS number	QA4690000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related compounds	titanium tetrachloride chromyl chloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Molybdenum pentachloride is the chemical compound with the formula MoCl₅. 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 Mo₂Cl₁₀, 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.

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Preparation and properties

MoCl₅ is prepared by chlorination of Mo metal but also chlorination of MoO₃. Notice that MoCl₆ cannot be prepared under normal conditions. In contrast, the heavier analogues WCl₆ is well known.

MoCl₅ is a strong oxidant, as indicated by its non-reactivity toward Cl₂. It is easily reduced by even MeCN to afford the adduct MoCl₄(MeCN)₂, which in turn reacts with THF to give MoCl₄(THF)₂, a very versatile reagent in the chemistry of molybdenum. MoCl₅ is reduced by HBr to form MoBr₄. The reaction is conducted in ethylbromide at -50 C:

2 MCl₅ + 10 HBr → 2 MoBr₄ + 10 HCl + Br₂

MoBr₄ reacts with THF to give the Mo(III) species mer-MoBr₃(THF)₃.

MoCl₅ is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form [MoCl₆]^-.

Safety considerations

MoCl₅ is an aggressive oxidant and readily hydrolyzes to release HCl.

References

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.

Categories: Molybdenum compounds | Chlorides | Metal halides

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Molybdenum(V)_chloride". A list of authors is available in Wikipedia.