Thorium(IV) chloride

Thorium(IV) chloride describes a family of inorganic compounds with the formula ThCl4(H2O)n. Both the anhydrous and tetrahydrate (n = 4) forms are known. They are hygroscopic, water-soluble white salts.

Structures
The structure of thorium(IV) chloride features 8-coordinate Th centers with doubly bridging chloride ligands.

Synthesis
ThCl4 was an intermediate in the original isolation of thorium metal by Jons Jacob Berzelius.

Thorium(IV) chloride can be produced in a variety of ways. One method is a carbothermic reaction, 700 °C to 2600 °C, involving thorium oxides and carbon in a stream of chlorine gas:
 * ThO2 +  2C  +  4Cl2  →  ThCl4  +  2CO

The chlorination reaction can be effected with carbon tetrachloride:
 * Th(C2O4)2 +  CCl4  →  ThCl4  +  3CO  +  3CO2

In another two-step method, thorium metal reacts with ammonium chloride:
 * Th +  6NH4Cl →  (NH4)2ThCl6 + 4NH3  +  2H2

The hexachloride salt is then heated at 350 °C under a high vacuum to produce ThCl4.

Reactions
ThCl4 reacts with Lewis bases to give molecular adducts, such as ThCl4(DME)2 and ThCl4(TMEDA)2.
 * Lewis base adducts

Thorium(IV) chloride is an intermediate in the purification of thorium, which can be affected by:
 * Reduction to Th metal
 * 1) Reduction of ThCl4 with alkali metals.
 * 2) Electrolysis of anhydrous thorium(IV) chloride in fused mixture of NaCl and KCl.
 * 3) Ca reduction of a mixture of ThCl4 with anhydrous zinc chloride.