Related compounds Molar mass 192.75 g/mol Density 1.82 g/cm³ | Formula VCl4 Boiling point 154 °C | |
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Appearance bright red liquid, moisture sensitive | ||
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 in this reaction; Cl2 lacks the oxidizing power to attack VCl4. VCl5 can be prepared indirectly, by metathesis of VF5 with BCl3 at −78 °C. 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 VCl4 + 8 HBr → 2 VBr3 + 8 HCl + Br2VCl4 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. It is reduced to VCl
3 in the process.
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.