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Molybdenum(V) chloride

Molybdenum(V) chloride
Systematic name Molybdenum(V) chloride
Other names Molybdenum pentachloride
Molecular formula MoCl5
Molar mass 273.21 g/mol
Appearance dark-green
moisture sensitive
CAS number [10241-05-1]
Density and phase 2.928 g/cm3
Solubility in water hydrolyzes
Other solvents chlorocarbons
Melting point 194 °C
Boiling point 268 °C
edge-shared bioctahedron
Crystal structure  ?
Dipole moment  ? D
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
n, εr, etc.
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.

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.


  • 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.
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.
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