Thiophosphoryl bromide

Thiophosphoryl bromide is an inorganic compound with the formula PSBr3.

Preparation
Thiophosphoryl bromide can be prepared by heating phosphorus tribromide with phosphorus pentasulfide, or with elemental sulfur in an inert atmosphere at 130 °C.

Thiophosphoryl bromide is one product of the bromination of P4S7 in cold carbon disulfide:


 * 3 P4S7 + 12 Br2 → 2 PBr3 + 2 PSBr3 + 2 P2S6Br2 + 2 P2S5Br4

Structure and properties
Thiophosphoryl bromide has tetrahedral molecular geometry and C3v molecular symmetry. According to gas electron diffraction, the phosphorus–sulfur bond length is 1.895 Å and the phosphorus–bromine bond length is 2.193 Å, while the S\dP\sBr bond angle is 116.2° and the Br\sP\sBr bond angle is 101.9°.

Thiophosphoryl bromide is soluble in carbon disulfide, chloroform and diethyl ether.

Reactions
Like other phosphoryl and thiophosphoryl halides, thiophosphoryl bromide readily hydrolyses, undergoes nucleophilic substitution and forms adducts with Lewis acids. Reaction with lithium iodide generates the mixed thiophosphoryl halides PSBr2I and PSBrI2 but not thiophosphoryl iodide, PSI3. Thiophosphoryl bromide is of use in organic synthesis for reducing sulfoxides to thioethers, and sulfines to thioketones.