Vanadium oxytrichloride

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Vanadium oxytrichloride
IUPAC name	Vanadium(V) oxide trichloride
Other names	Vanadium oxytrichloride Vanadyl chloride Vanadyl trichloride
Identifiers
CAS number	[7727-18-6]
RTECS number	YW2975000
SMILES	VOClClCl
Properties
Molecular formula	VOCl3
Molar mass	173.30 g/mol
Appearance	Yellow to brown liquid
Density	1.84 g/cm3, liquid
Melting point	-76.5 °C
Boiling point	126–127 °C (400 K)
Solubility in water	Decomposes
Solubility in other solvents	chlorinated solvents
Structure
Molecular shape	Tetrahedral
Hazards
Main hazards	Toxic, hydrolysis to HCl
NFPA 704	1 3 3
R-phrases	R14 R25 R34
S-phrases	S26 S27 S28 S36/37/39 S45
Related compounds
Related vanadium compounds	Vanadium(V) oxide Vanadium tetrachloride Vanadium oxytrifluoride
Related compounds	Phosphorus oxytrichloride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Vanadium oxytrichloride is the inorganic compound with the formula VOCl₃. This distillable liquid hydrolyzes readily in air and is a strong oxidant. It is used as a reagent in organic synthesis.^[1]

Contents 1 Properties 2 Preparation 3 Reactions 3.1 Hydrolysis and alcoholysis 3.2 Interconversions to other V-O-Cl compounds 3.3 Adduct formation 3.4 VOCl3 in alkene polymerization 4 References

[edit] Properties

VOCl₃ is a vanadium(V) compound and as such is diamagnetic. It is tetrahedral with O-V-Cl bond angles of 111° and Cl-V-Cl bond angles of 108°. The V-O and V-Cl bond lengths are 157 and 214 pm, respectively. VOCl₃ is highly reactive toward water and evolves Cl₂ upon standing. It is soluble in nonpolar solvents such as benzene, CH₂Cl₂, and hexane. In some aspects, the chemical properties of VOCl₃ and POCl₃ are similar. One distinction is that VOCl₃ is a strong oxidizing agent, whereas the phosphorus compound is not.^[2]

[edit] Preparation

VOCl₃ is synthesized by the chlorination of V₂O₅. The reaction proceeds at ca. 600 °C:^[3]

3 Cl₂ + V₂O₅ → 2 VOCl₃ + 1.5 O₂

When the V₂O₅ is used as an intimate mixture with carbon, the synthesis proceeds at 200-400 °C; in this case the carbon serves as a deoxygenation agent akin to its use in the Kroll process for the manufacturing of TiCl₄ from TiO₂.

Vanadium(III) oxide can also be used as a precursor:

3 Cl₂ + V₂O₃ → 2 VOCl₃ + 0.5 O₂

A more typical laboratory synthesis entails chlorination of V₂O₅ using SOCl₂.^[4]

V₂O₅ + 3 SOCl₂ → 2 VOCl₃ + 3 SO₂

[edit] Reactions

[edit] Hydrolysis and alcoholysis

Vanadium oxytrichloride quickly hydrolyzes resulting in vanadium pentoxide and hydrochloric acid. In the picture, orange V₂O₅ can be seen forming on the walls of the beaker. An intermediate in this process is VO₂Cl:

2 VOCl₃ + 3 H₂O → V₂O₅ + 6 HCl

VOCl₃ react with alcohols especially in the presence of a proton-acceptor (e.g. Et₃N) to give alkoxides:

VOCl₃ + 3 ROH → VO(OR)₃ + 3 HCl (R = Me, Ph, etc.)

[edit] Interconversions to other V-O-Cl compounds

VOCl₃ is also used in the synthesis of VOCl₂.

V₂O₅ + 3 VCl₃ + VOCl₃ → 6 VOCl₂

Dioxovanadium monochloride can be prepared by an unusual reaction involving Cl₂O.^[5]

VOCl₃ + Cl₂O → VO₂Cl + 2 Cl₂

At >180 °C, VO₂Cl decomposes to V₂O₅ and VOCl₃. Similarly, VOCl₂ also decomposes to give VOCl₃, together with VOCl.

[edit] Adduct formation

VOCl₃ is strongly Lewis acidic, as demonstrated by its tendency to form adducts with various bases such as MeCN and amines. In forming the adducts, vanadium changes from four-coordinate tetrahedral geometry to six-coordinate octahedral geometry:

VOCl₃ + 2 H₂NEt → VOCl₃(H₂NEt)₂

[edit] VOCl₃ in alkene polymerization

VOCl₃ is used as a catalyst or precatalytst in production of ethylene-propylene rubbers (EPDM).

[edit] References