- Vanadium tetrachloride
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Vanadium tetrachloride Vanadium tetrachloride
Vanadium(IV) chlorideIdentifiers CAS number 7632-51-1 PubChem 24273 ChemSpider 19956660 RTECS number YW2625000 Jmol-3D images Image 1 - [V+2].[V+2].[Cl-].[Cl-].[Cl-].[Cl-]
Properties Molecular formula VCl4 Molar mass 192.75 g/mol Appearance bright red liquid, moisture sensitive Density 1.816 g/cm3, liquid Melting point −28 °C
Boiling point 154 °C
Solubility in water decomposes Solubility in other solvents chlorocarbons Vapor pressure 7.9 Pa Structure Coordination
geometrytetrahedral Dipole moment 0 D Hazards EU Index Not listed Main hazards oxidizer; hydrolyzes to release HCl NFPA 704 Related compounds Other anions vanadium tetrafluoride, vanadium disulfide, vanadium tetrabromide Other cations titanium tetrachloride, chromium tetrachloride, niobium tetrachloride, tantalum tetrachloride Related compounds vanadium trichloride tetrachloride (verify) (what is:
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)Infobox references Vanadium tetrachloride is the inorganic compound with the formula VCl4. This bright red liquid is a useful reagent for the preparation of other vanadium compounds.
Contents
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; Cl2 lacks the oxidizing power to attack VCl4. In contrast, the heavier analogues NbCl5 and TaCl5 are stable and not particularly oxidizing. Of course, VF5 does exist, 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 vanadium(III) chloride.
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.[1]
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- 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.
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.
Organic chemistry
In organic synthesis, VCl4 is used to couple phenols. For example, it converts phenol into 4,4'-biphenol.[2] It is reduced to VCl3 in the process.
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- 2 C6H5OH + 2 VCl4 → HOC6H4–C6H4OH + 2 VCl3 + 2 HCl
This reaction highlights the oxidizing ability of VCl4, consistent with it being resistant to further oxidation by Cl2.
Safety considerations
VCl4 is a volatile, aggressive oxidant that readily hydrolyzes to release HCl.
References
- ^ Calderazzo, F.; Maichle-Mossmer, C.; Pampaloni, G. and Strähle, J. (1993). "Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange". Dalton Transactions: 655–8. doi:10.1039/DT9930000655.
- ^ M. K. O’Brien, B. Vanasse, “Vanadium(IV) Chloride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York.
Vanadium compounds Categories:- Vanadium compounds
- Chlorides
- Metal halides
- Reagents for organic chemistry
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