Molybdenum tetrachloride

Molybdenum tetrachloride is the inorganic compound with the empirical formula MoCl4. The material exists as two polymorphs, both being dark-colored paramagnetic solids. These compounds are mainly of interest as precursors to other molybdenum complexes.

Molybdenum tetrachloride
Molybdenum tetrachloride
Names
IUPAC name
Molybdenum tetrachloride
Other names
Molybdenum(IV) chloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.033.039
UNII
  • InChI=1S/4ClH.Mo/h4*1H;/q;;;;+4/p-4 ☒N
    Key: OYMJNIHGVDEDFX-UHFFFAOYSA-J ☒N
  • InChI=1/4ClH.Mo/h4*1H;/q;;;;+4/p-4/rCl4Mo/c1-5(2,3)4
    Key: OYMJNIHGVDEDFX-DFQGPNMMAB
  • Cl[Mo](Cl)(Cl)Cl
Properties
Cl4Mo
Molar mass 237.752 g/mol
Appearance black solid
Melting point 552 °C (1,026 °F; 825 K)
Decomposes
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
3
0
1
Flash point Non flammable
Related compounds
Related compounds
 Molybdenum(II) chloride
Molybdenum(III) chloride
Molybdenum(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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Infobox references

Structure

The α polymorph is a polymer. The β polymorph is a hexamer. In both polymorph, the Mo center is octahedral with two terminal chloride ligands and four doubly bridging ligands.[1] In addition to these two binary phases, a number of adducts are know with the formula MoCl4L2 where L is a Lewis base.

Preparation

α-Molybdenum tetrachloride can be prepared from by dechlorination of molybdenum pentachloride using tetrachloroethene:[2]

2 MoCl5 + C2Cl4 → 2 MoCl4 + C2Cl6

Heating α-molybdenum tetrachloride in a sealed container in the presence of molybdenum pentachloride induces conversion to the β polymorph.[2]

Reactions

When heated in an open container, molybdenum tetrachloride evolves chlorine, giving molybdenum trichloride;[2]

2 MoCl4 → 2 MoCl3 + Cl2

The acetonitrile complex adduct can be prepared by reduction of the pentachloride with acetonitrile:[3][4]

2 MoCl5 + 5 CH3CN → 2 MoCl4(CH3CN)2 + ClCH2CN + HCl

The MeCN ligands can be exchanged with other ligands:

MoCl4(CH3CN)2 + 2 THF → MoCl4(THF)2 + 2 CH3CN

The pentachloride can be reduced to the ether complex MoCl4(Et2O)2 using tin powder. It is a beige, paramagnetic solid.[5]

References
  1. Ulrich Müller (1981). "Hexameric Molybdenum Tetrachloride". Angewandte Chemie International Edition in English. 20 (8): 692. doi:10.1002/anie.198106921.
  2. McCann III, E. L.; Brown, T. M. (1970). "Molybdenum(IV) Chloride". Inorganic Syntheses. Inorganic Syntheses. Vol. 12. p. 181. doi:10.1002/9780470132432.ch31. ISBN 9780470132432.
  3. Broderick, Erin M.; Browne, Samuel C.; Johnson, Marc J. A. (2014). "Dimolybdenum and Ditungsten Hexa(Alkoxides)". Inorganic Syntheses: Volume 36. Inorganic Syntheses. Vol. 36. pp. 95–102. doi:10.1002/9781118744994.ch18. ISBN 9781118744994.
  4. Dilworth, Jonathan R.; Richards, Raymond L. (1990). "The Synthesis of Molybdenum and Tungsten Dinitrogen Complexes". Inorganic Syntheses. Inorganic Syntheses. Vol. 28. p. 33. doi:10.1002/9780470132593.ch7. ISBN 9780470132593.
  5. Maria, Sébastien; Poli, Rinaldo (2014). "Ether Complexes of Molybdenum(III) and Molybdenum(IV) chlorides". Inorganic Syntheses: Volume 36. Inorganic Syntheses. Vol. 36. pp. 15–18. doi:10.1002/9781118744994.ch03. ISBN 9781118744994.
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