Molybdenum(V) chloride
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 Partially oxidized MoCl5
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| IUPAC names
Molybdenum(V) chloride
Molybdenum pentachloride | |
| Identifiers | |
3D model (JSmol)
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| ECHA InfoCard | 100.030.510 |
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| Mo2Cl10 | |
| Molar mass | 273.21 g/mol (MoCl5) |
| Appearance | dark-green solid hygroscopic paramagnetic |
| Density | 2.928 g/cm3 |
| Melting point | 194 °C (381 °F; 467 K) |
| Boiling point | 268 °C (514 °F; 541 K) |
| hydrolyzes | |
| Solubility | soluble in dry ether, dry alcohol, organic solvents |
| Structure | |
| monoclinic | |
| edge-shared bioctahedron | |
| Hazards | |
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Main hazards
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oxidizer, hydrolyzes to release HCl |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
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Other cations
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Related molybdenum chlorides
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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 empirical formula MoCl5. This dark volatile solid is used in research to prepare other molybdenum compounds. It is moisture-sensitive and soluble in chlorinated solvents.
Structure
[edit]Usually called molybdenum pentachloride, it is in fact partly a dimer with the molecular formula Mo2Cl10.[1] In the dimer, each molybdenum has local octahedral symmetry and two chlorides bridge between the molybdenum centers.[2] A similar structure is also found for the pentachlorides of W, Nb and Ta.[3] In the gas phase and partly in solution, the dimers partially dissociate to give a monomeric MoCl5.[4] The monomer is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is +5, leaving one valence electron on the metal center.
Preparation and properties
[edit]MoCl5 is prepared by chlorination of Mo metal but also chlorination of MoO3. The unstable hexachloride MoCl6 is not produced in this way.[5]
MoCl5 is reduced by acetonitrile to afford an orange acetonitrile complex, MoCl4(CH3CN)2. This complex in turn reacts with THF to give MoCl4(THF)2, a precursor to other molybdenum-containing complexes.[6]
Molybdenum(IV) bromide is prepared by treatment of MoCl5 with hydrogen bromide:
- 2 MoCl5 + 10 HBr → 2 MoBr4 + 10 HCl + Br2
The reaction proceeds via the unstable molybdenum(V) bromide, which releases bromine at room temperature.[7]
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, deoxygenation, and oxidative coupling reactions.[8]
Reactions
[edit]MoCl5 is reduced by acetonitrile:[9]
- 2 MoCl5 + 5 CH3CN → 2 MoCl4(CH3CN)2 + HCl + ClCH2CN
Although it polymerizes tetrahydrofuran, MoCl5 is stable in diethyl ether. Reduction of such solutions with tin gives MoCl4((CH3CH2)2O)2 and MoCl3((CH3CH2)2O)3, depending on conditions.[10]
Safety considerations
[edit]MoCl5 is an aggressive oxidant and readily hydrolyzes to release HCl.
See also
[edit]References
[edit]- ^ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego, CA: Academic Press. ISBN 0-12-352651-5.
- ^ Beck, J.; Wolf, F. (1997). "Three New Polymorphic Forms of Molybdenum Pentachloride". Acta Crystallogr. B53 (6): 895–903. doi:10.1107/S0108768197008331. S2CID 95489209.
- ^ Wells, A. E. (1984). Structural Inorganic Chemistry (5th ed.). Oxford: Clarendon Press.
- ^ Brunvoll, J.; Ischenko, A. A.; Spiridonov, V. P.; Strand, T. G. (1984). "Composition and Molecular Structure of Gaseous Molybdenum Pentachloride by Electron Diffraction". Acta Chem. Scand. A38: 115–120. doi:10.3891/acta.chem.scand.38a-0115.
- ^ Tamadon, Farhad; Seppelt, Konrad (2013). "The Elusive Halides VCl5, MoCl6, and ReCl6". Angew. Chem. Int. Ed. 52 (2): 767–769. doi:10.1002/anie.201207552. PMID 23172658.
- ^ Dilworth, Jonathan R.; Richards, Raymond L. (1990). "The Synthesis of Molybdenum and Tungsten Dinitrogen Complexes". Inorganic Syntheses. Inorganic Syntheses. Vol. 28. pp. 33–43. doi:10.1002/9780470132593.ch7. ISBN 9780470132593.
- ^ Calderazzo, Fausto; Maichle-Mössmer, Cäcilie; Pampaloni, Guido; Strähle, Joachim (1993). "Low-Temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange". J. Chem. Soc., Dalton Trans. (5): 655–658. doi:10.1039/DT9930000655.
- ^ Kauffmann, T.; Torii, S.; Inokuchi, T. (2004). "Molybdenum(V) Chloride". Encyclopedia of Reagents for Organic Synthesis. New York, NY: J. Wiley & Sons. doi:10.1002/047084289X. hdl:10261/236866. ISBN 9780471936237.
- ^ Dilworth, Jonathan R.; Richards, Raymond L. (1990). The Synthesis of Molybdenum and Tungsten Dinitrogen Complexes. Inorganic Syntheses. Vol. 28. pp. 33–43. doi:10.1002/9780470132593.ch7. ISBN 9780470132593.
- ^ Maria, Sébastien; Poli, Rinaldo (2014). "Ether Complexes of Molybdenum(III) and Molybdenum(IV) chlorides". Inorganic Syntheses: Volume 36 (PDF). Inorganic Syntheses. Vol. 36. pp. 15–18. doi:10.1002/9781118744994.ch03. ISBN 9781118744994.