Vanadium oxytrichloride

Vanadium oxytrichloride
Vanadium oxytrichloride
Identifiers
CAS number 7727-18-6 YesY
PubChem 24410
RTECS number YW2975000
Properties
Molecular formula VOCl3
Molar mass 173.30 g/mol
Appearance Yellow to brown liquid
Density 1.826 g/cm3, liquid
Melting point

-76.5 °C, 197 K, -106 °F

Boiling point

126.7 °C, 400 K, 260 °F

Solubility in water Decomposes
Solubility in other solvents chlorinated solvents
Vapor pressure 8.1 Pa (20 °C)
Structure
Molecular shape Tetrahedral
Hazards
EU Index Not listed
Main hazards Toxic, hydrolysis to HCl
NFPA 704
NFPA 704.svg
1
3
3
LD50 140 mg/kg (oral in rats)
Related compounds
Related vanadium compounds Vanadium(V) oxide
Vanadium tetrachloride
Vanadium oxytrifluoride
Related compounds Phosphoryl chloride
 YesY oxytrichloride (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox 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

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]

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 involves the chlorination of V2O5 using SOCl2.[4]

V2O5 + 3 SOCl2 → 2 VOCl3 + 3 SO2

Reactions

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 reacts 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.)

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.

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

VOCl3 in alkene polymerization

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

References

  1. ^ M. O'Brien, B. Vanasse (2001). Encyclopedia of Reagents for Organic Synthesis. 
  2. ^ A. Earnshaw, N. Greenwood (1997). The Chemistry of the Elements - Second Edition. pp. 513–514. 
  3. ^ A. Holleman, E. Wiberg (2001). Inorganic Chemistry. 
  4. ^ S. Tyree (1967). Inorganic Syntheses Volume IX. p. 80. 
  5. ^ H. Oppermann, "Gleichgewichte mit VOCl3, VO2Cl, VOCl2" Zeitschrift für Anorganische und Allgemeine Chemie, vol. 331. 113-126 (1967)

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