Antimony pentachloride is a chemical compound with the formula SbCl<sub>5</sub>. It is a colourless oil, but typical samples are yellowish due to dissolved chlorine. Owing to its tendency to hydrolyse to hydrochloric acid, SbCl<sub>5</sub> is a highly corrosive substance and must be stored in glass or PTFE containers.
Antimony pentachloride is prepared by passing chlorine gas into molten antimony trichloride:
Gaseous SbCl<sub>5</sub> has a trigonal bipyramidal structure.
This compounds reacts with water to form antimony pentoxide and hydrochloric acid:
The mono- and tetrahydrates are known, SbCl<sub>5</sub>÷H<sub>2</sub>O and SbCl<sub>5</sub>÷4H<sub>2</sub>O.
This compound forms adducts with many Lewis bases. SbCl<sub>5</sub> is a soft Lewis acid and its ECW model parameters are E<sub>A</sub> = 3.64 and C<sub>A</sub> = 10.42. It is used as the standard Lewis acid in the Gutmann scale of Lewis basicity.
It is also a strong oxidizing agent. For example aromatic ethers are oxidized to their radical cations according to the following stoichiometry:
Antimony pentachloride is used as a polymerization catalyst and for the chlorination of organic compounds.
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.