Antimony pentachloride explained

Antimony pentachloride is a chemical compound with the formula SbCl5. It is a colourless oil, but typical samples are yellowish due to dissolved chlorine. Owing to its tendency to hydrolyse to hydrochloric acid, SbCl5 is a highly corrosive substance and must be stored in glass or PTFE containers.

Preparation and structure

Antimony pentachloride is prepared by passing chlorine gas into molten antimony trichloride:

SbCl3 + Cl2 → SbCl5

Gaseous SbCl5 has a trigonal bipyramidal structure.

Reactions

This compounds reacts with water to form antimony pentoxide and hydrochloric acid:[1]

2 SbCl5 + 5 H2O → Sb2O5 + 10 HCl

The mono- and tetrahydrates are known, SbCl5·H2O and SbCl5·4H2O.

This compound forms adducts with many Lewis bases. SbCl5 is a soft Lewis acid and its ECW model parameters are EA = 3.64 and CA = 10.42. It is used as the standard Lewis acid in the Gutmann scale of Lewis basicity.[2] [3]

It is also a strong oxidizing agent.[4] For example aromatic ethers are oxidized to their radical cations according to the following stoichiometry:[5]

3SbCl5 + 2 ArH → 2(ArH+)(SbCl6) + SbCl3

Applications

Antimony pentachloride is used as a polymerization catalyst and for the chlorination of organic compounds.

Precautions

Antimony pentachloride is a highly corrosive substance that should be stored away from heat and moisture. It is a chlorinating agent and, in the presence of moisture, it releases hydrogen chloride gas. Because of this, it may etch even stainless-steel tools (such as needles), if handled in a moist atmosphere. It should not be handled with non-fluorinated plastics (such as plastic syringes, plastic septa, or needles with plastic fittings), since it melts and carbonizes plastic materials.[6]

Notes and References

  1. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002,
  2. V. Gutmann . . 18 . 1976 . 225–255 . 10.1016/S0010-8545(00)82045-7 . Solvent effects on the reactivities of organometallic compounds . 2.
  3. Cramer, R. E. . Bopp, T. T. . 1977. Graphical display of the enthalpies of adduct formation for Lewis acids and bases . Journal of Chemical Education . 54. 612–613. 10.1021/ed054p612. The plots shown in this paper used older parameters. Improved E&C parameters are listed in ECW model.
  4. Connelly, N. G. . Geiger, W. E. . Chemical Redox Agents for Organometallic Chemistry . . 1996 . 96 . 2 . 877–922 . 10.1021/cr940053x . 11848774.
  5. 10.1021/jo980407a. Preparation and Structures of Crystalline Aromatic Cation-Radical Salts. Triethyloxonium Hexachloroantimonate as a Novel (One-Electron) Oxidant. 1998. Rathore. R.. Kumar. A. S.. Lindeman. S. V.. Kochi. J. K.. The Journal of Organic Chemistry. 63. 17. 5847–5856. 11672186.
  6. Shekarchi, M.; Behbahani, F. K Catal. Lett. 2017 147 2950. doi:10.1007/s10562-017-2194-2