Molybdenum(V) chloride
| Names | |
|---|---|
| IUPAC names
Molybdenum(V) chloride
Molybdenum pentachloride | |
| Identifiers | |
| ECHA InfoCard | 100.030.510 |
| RTECS number |
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CompTox Dashboard (EPA)
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| Properties | |
| 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 |
| hydrolyzes | |
| Solubility | soluble in dry ether, dry alcohol, organic solvents |
| Structure | |
| monoclinic | |
| edge-shared bioctahedron | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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oxidizer, hydrolyzes to release HCl |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
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Molybdenum(V) fluoride Molybdenum(IV) bromide Molybdenum(III) iodide |
Other cations
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Chromium(IV) chloride Tungsten(V) chloride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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
- ^ 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-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
- ^ 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.