Thorium(IV) bromide

Thorium(IV) bromide is an inorganic compound, with the chemical formula of ThBr4.

Preparation
Thorium(IV) bromide can be obtained by reacting thorium dioxide, bromine and carbon at 800~900 °C. This method produces a mixture of alpha and beta forms of thorium bromide. The pure α-form product is obtained by heating the mixture at 330~375 °C for a long time. The pure β form is obtained by heating the product to 470 °C and then rapidly cooling it in ice water.


 * ThO2 + 2 C + 2 Br2 ⟶ ThBr4 + 2 CO

Thorium(IV) bromide can also be produced by the reaction of thorium and bromine. Thorium hydroxide reacts with hydrobromic acid to crystallize hydrates from the solution.

Properties
Thorium(IV) bromide exists in low-temperature α-type and high-temperature β-type. They are both white deliquescent solids and are easily soluble in water, ethanol and ethyl acetate. It reacts with fluorine gas under standard conditions and with chlorine or oxygen when heated. The beta form of thorium bromide is metastable at room temperature and converts to the alpha form over 10 to 12 weeks, with the conversion from alpha to beta occurring at around 420 °C. The α-type thorium(IV) bromide is an orthorhombic crystal, while the β-type thorium(IV) bromide is a tetragonal crystal with space group I41/amd. Some of its hydrates are known, and these hydrates form thorium oxybromide on heating.