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
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

Structure of β-MoCl4

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]