Thorium(IV) chloride explained

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

thumb|left|162px|Alternative view of the structure of solid ThCl₄.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 + 2H₂The hexachloride salt is then heated at 350 °C under a high vacuum to produce ThCl₄.

Reactions

Lewis base adductsThCl₄ reacts with Lewis bases to give molecular adducts, such as ThCl₄(DME)₂ and ThCl₄(TMEDA)₂.^[5]

Reduction to Th metalThorium(IV) chloride is an intermediate in the purification of thorium, which can be affected by:

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.^[6]

Notes and References

1. 10.1016/0022-5088(74)90224-0. Crystal Structures of ThCl₄ Polymorphs. 1974. Mason. J. T.. Jha. M. C.. Chiotti. P.. Journal of the Less Common Metals. 34. 143–151.
2. 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. 10.1021/ed009p1231. 1932JChEd...9.1231W. 0021-9584.
3. Book: Brauer, Georg. Handbook Of Preparative Inorganic Chemistry. Academic Press. 1963. New York.
4. Gutierrez. R. L.. Herbst. R. J.. October 1979. Preliminary Fabrication Studies of Alternative LMFBR Carbide Fuels. Los Alamos Scientific Laboratory. 10.2172/5688597 .
5. Cantat. Thibault. Scott. Brian L.. Kiplinger. Jaqueline L.. 2010-01-25. Convenient Access to the Anhydrous Thorium Tetrachloride Complexes ThCl₄(DME)₂, ThCl₄(1,4-dioxane)₂ and ThCl₄(THF)_3.5 using Commercially Available and Inexpensive Starting Materials. Chemical Communications. en. 46. 6. 919–21. 10.1039/b923558b. 20107650. 1364-548X.
6. Web site: Periodic Table of Elements: Los Alamos National Laboratory. periodic.lanl.gov. 2016-04-29.