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

Names
IUPAC name Molybdenum tetrachloride
Other names Molybdenum(IV) chloride
Identifiers
CAS Number	13320-71-3 Y
3D model (JSmol)	Interactive image
ChemSpider	75200 N
ECHA InfoCard	100.033.039
PubChem CID	83340
UNII	6417YBA168 Y
CompTox Dashboard (EPA)	DTXSID90928002
InChI 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
SMILES Cl[Mo](Cl)(Cl)Cl
Properties
Chemical formula	MoCl4
Molar mass	237.752 g/mol
Appearance	black solid
Melting point	552 °C (1,026 °F; 825 K)
Solubility in water	Decomposes
Hazards
NFPA 704 (fire 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). N verify (what is YN ?) 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.