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.[1]
Synthesis
ThCl4 was an intermediate in the original isolation of thorium metal by Jons Jacob Berzelius.[2]
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:[3][4]
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.[5]
Reactions
Lewis base adducts
ThCl4 reacts with Lewis bases to give molecular adducts, such as ThCl4(DME)2 and ThCl4(TMEDA)2.[5]
Reduction to Th metal
Thorium(IV) chloride is an intermediate in the purification of thorium, which can be affected by:
Reduction of ThCl4 with alkali metals.
Electrolysis of anhydrous thorium(IV) chloride in fused mixture of NaCl and KCl.
Ca reduction of a mixture of ThCl4 with anhydrous zinc chloride.[6]
References
^Mason, J. T.; Jha, M. C.; Chiotti, P. (1974). "Crystal Structures of ThCl4 Polymorphs". Journal of the Less Common Metals. 34: 143–151. doi:10.1016/0022-5088(74)90224-0.
^Weeks, Mary Elvira (1932-07-01). "The Discovery of the Elements. XI. Some Elements Isolated with the Aid of Potassium and Sodium: Zirconium, Titanium, Cerium, and Thorium". Journal of Chemical Education. 9 (7): 1231. Bibcode:1932JChEd...9.1231W. doi:10.1021/ed009p1231. ISSN0021-9584.
^Brauer, Georg (1963). Handbook Of Preparative Inorganic Chemistry. New York: Academic Press.