Molybdenum(V) chloride

Molybdenum(V) chloride
IUPAC name

Molybdenum(V) chloride
Molybdenum pentachloride
Identifiers
CAS number 10241-05-1 Y
RTECS number QA4690000
Properties
Molecular formula Cl10Mo2
Molar mass 273.21 g/mol
Appearance dark-green solid
hygroscopic
paramagnetic
Density 2.928 g/cm3
Melting point

194 °C
Boiling point

268 °C
Solubility in water hydrolyzes
Solubility soluble in dry ether, dry alcohol, organic solvents
Structure
Crystal structure monoclinic
Coordination
geometry		 edge-shared bioctahedron
Hazards
EU Index Not listed
Main hazards oxidizer, hydrolyzes to release HCl
Flash point Non-flammable
Related compounds
Other anions Molybdenum(V) fluoride
Molybdenum(IV) bromide
Molybdenum(III) iodide
Other cations Chromium(IV) chloride
Tungsten(V) chloride
Related molybdenum chlorides Molybdenum(II) chloride
Molybdenum(III) chloride
Molybdenum(IV) chloride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Molybdenum(V) chloride is the inorganic compound with the formula [MoCl5]2. 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 pentachlorides of W, Nb and Ta. 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.[1]

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 versatile reagent in the chemistry of molybdenum.[2] MoCl5 is reduced by HBr to form MoBr4. The reaction is conducted in ethylbromide at -50 C:

2 MoCl5 + 10 HBr → 2 MoBr4 + 10 HCl + Br2

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

MoCl5 is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form [MoCl6]-. In organic synthesis, the compound finds occasional use in chlorinations and deoxygenation reactions.[4]

Safety considerations

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

References

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ 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.
  3. ^ Calderazzo, F.; Maichle-Mössmer, C.; Pampaloni, G.; 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.doi:10.1039/DT9930000655
  4. ^ T. Kauffmann, S. Torii, T. Inokuchi “Molybdenum(V) Chloride” in Encyclopedia of Reagents for Organic Synthesis 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.