Vanadium tetrachloride

Vanadium tetrachloride
Structural formula of the vanadium tetrachloride molecule	3D model of the vanadium tetrachloride molecule
Names
	IUPAC names Vanadium tetrachloride; Vanadium(IV) chloride
Identifiers
CAS Number	7632-51-1 ;
3D model (JSmol)	Interactive image;
ChemSpider	19956660 ;
ECHA InfoCard	100.028.692
EC Number	231-561-1;
PubChem CID	24273;
RTECS number	YW2625000;
UNII	2I17MGM5YJ ;
CompTox Dashboard (EPA)	DTXSID0064757 ;
	InChI InChI=1S/4ClH.2V/h41H;;/q;;;;2+2/p-4 Key: UNUHYFVFMNJHJW-UHFFFAOYSA-J ; InChI=1/4ClH.2V/h41H;;/q;;;;2+2/p-4 Key: UNUHYFVFMNJHJW-XBHQNQODAR;
	SMILES Cl[V](Cl)(Cl)Cl;
Properties
Chemical formula	VCl4
Molar mass	192.75 g/mol
Appearance	bright red liquid, moisture sensitive
Odor	pungent
Density	1.816 g/cm3, liquid
Melting point	−24.5 °C (−12.1 °F; 248.7 K)
Boiling point	148 °C (298 °F; 421 K)
Solubility in water	decomposes
Solubility	soluble in CH2Cl2
Vapor pressure	7.9 Pa
Magnetic susceptibility (χ)	+1130.0·10−6 cm3/mol
Structure
Coordination geometry	tetrahedral
Dipole moment	0 D
Hazards
Main hazards	toxic; oxidizer; hydrolyzes to release HCl
NFPA 704 (fire diamond)	0 3 2 W
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	160 mg/kg (rat, oral)
Related compounds
Other anions	vanadium tetrafluoride, vanadium disulfide, vanadium tetrabromide
Other cations	titanium tetrachloride, chromium tetrachloride, niobium tetrachloride, tantalum tetrachloride
Related compounds	vanadium trichloride
	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

Vanadium tetrachloride is the inorganic compound with the formula V Cl₄. This bright red liquid serves as a useful reagent for the preparation of other vanadium compounds.

Synthesis, bonding, basic properties

With one more valence electron than diamagnetic TiCl₄, VCl₄ is a paramagnetic liquid. It is one of only a few paramagnetic compounds that is liquid at room temperature.

VCl₄ is prepared by chlorination of vanadium metal. VCl₅ does not form in this reaction; Cl₂ lacks the oxidizing power to attack VCl₄. VCl₅ can however be prepared indirectly from VF₅ at −78 °C.[1] In contrast, the heavier analogues NbCl₅ and TaCl₅ are stable and not particularly oxidizing. VF₅ can be prepared directly by fluorination of vanadium metal, reflecting the increased oxidizing power of F₂ vs Cl₂. Indicative of its oxidizing power, VCl₄ releases Cl₂ at its boiling point (standard pressure) to afford VCl₃.

Reactions

Consistent with its high oxidizing power, VCl₄ reacts with HBr at -50 °C to produce VBr₃. The reaction proceeds via VBr₄, which releases Br₂ during warming to room temperature.[2]

2 VCl₄ + 8 HBr → 2 VBr₃ + 8 HCl + Br₂

VCl₄ forms adducts with many donor ligands, for example, VCl₄(THF)₂.

It is the precursor to vanadocene dichloride.

Organic chemistry

In organic synthesis, VCl₄ is used for the oxidative coupling of phenols. For example, it converts phenol into a mixture of 4,4'-, 2,4'-, and 2,2'-biphenols:[3]

2 C₆H₅OH + 2 VCl₄ → HOC₆H₄–C₆H₄OH + 2 VCl₃ + 2 HCl

Applications

VCl₄ is a catalyst for the polymerization of alkenes, especially those useful in the rubber industry. The underlying technology is related to Ziegler–Natta catalysis, which involves the intermediacy of vanadium alkyls.

Safety considerations

VCl₄ is a volatile, aggressive oxidant that readily hydrolyzes to release HCl.

References

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.
Calderazzo, F.; Maichle-Mössmer, C.; G., Pampaloni; J., Strähle (1993). "Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange". Dalton Transactions (5): 655–8. doi:10.1039/DT9930000655.
O’Brien, M. K.; Vanasse, B. (2004). "Vanadium(IV) Chloride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York, NY: J. Wiley & Sons. doi:10.1002/047084289X.rv001. ISBN 0471936235.

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[1] 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.

[2] Calderazzo, F.; Maichle-Mössmer, C.; G., Pampaloni; J., Strähle (1993). "Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange". Dalton Transactions (5): 655–8. doi:10.1039/DT9930000655.

[3] O’Brien, M. K.; Vanasse, B. (2004). "Vanadium(IV) Chloride". In Paquette, L. (ed.). Encyclopedia of Reagents for Organic Synthesis. New York, NY: J. Wiley & Sons. doi:10.1002/047084289X.rv001. ISBN 0471936235.