Uranium(III) chloride explained

Uranium(III) chloride, UCl₃, is a water soluble salt of uranium. UCl₃ is used mostly to reprocess spent nuclear fuel. Uranium(III) chloride is synthesized in various ways from uranium(IV) chloride; however, UCl₃ is less stable than UCl₄.

Preparation

There are two ways to synthesize uranium(III) chloride. The following processes describe how to produce uranium(III) chloride.

(1) In a mixture of NaCl-KCl at 670–710 °C, add uranium tetrachloride with uranium metal.

3UCl₄ + U → 4UCl₃^[1]

(2) Heat uranium(IV) chloride in hydrogen gas.

2UCl₄ + H₂ → 2UCl₃ + 2HCl^[2]

Properties

In solid uranium(III) chloride each uranium atom has nine chlorine atoms as near neighbours, at approximately the same distance, in a tricapped trigonal prismatic configuration.^[3]

Uranium(III) chloride is a green crystalline solid at room temperature. UCl₃ melts at 837 °C and boils at 1657 °C. Uranium(III) chloride has a density of 5500 kg/m³ or 5.500 g/cm³.

Its composition by weight:

Chlorine: 30.84%

Uranium: 69.16%

Its formal oxidative states:

Chlorine: −1

Uranium: +3

This salt is very soluble in water and is also very hygroscopic. UCl₃ is more stable in a solution of hydrochloric acid.^[4]

Uses

Reagent

Uranium(III) chloride is used in reactions with tetrahydrofuran (THF) and sodium methylcyclopentadiene to prepare various uranium metallocene complexes.^[5]

Catalyst

Uranium(III) chloride is used as a catalyst during reactions between lithium aluminium hydride (LiAlH₄) and olefins to produce alkyl aluminate compounds.^[6]

Molten form

The molten form of uranium(III) chloride is a typical compound in pyrochemical processes as it is important in the reprocessing of spent nuclear fuels.^[7] UCl₃ is usually the form that uranium takes as spent fuel in electrorefining processes.^{[7] [8]}

Hydrates

There are three hydrates of uranium(III) chloride:

1. UCl₃^.2H₂O^.2CH₃CN
2. UCl₃^.6H₂O
3. UCl₃^.7H₂O

Each are synthesized by the reduction of uranium(IV) chloride in methylcyanide (acetonitrile), with specific amounts of water and propionic acid.^[9]

Precautions

While there are no long-term data on the toxic effects thas UCl₃, it is important to minimize exposure to this compound when possible.

Similar to other uranium compounds that are soluble in water, UCl₃ is likely absorbed into the blood through the alveolar pockets of the lungs within days of exposure. Exposure to uranium(III) chloride leads to toxicity of the renal system.^[10]

References

1. Serrano, K.; Taxil, P.; Dugne, O.; Bouvet, S.; Puech, E. J. Nucl. Mater. 2000, 282, 137–145.
2. Remsen, Ira. Inorganic Chemistry. New York: Henry Holt and Company, 1890.
3. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications
4. Comey, Arthur M.; Hahn, Dorothy A. A Dictionary of Chemical Solubilities: Inorganic. New York: The MacMillan Company, 1921.
5. Brenna, J.G.; Anderson, R.A.; Zalkin, A. Inorg. Chem. 1986, 25, 1756–1760.
6. Le Marechal, J.F.; Ephritikhine, M.; Folcher, G. J. Organomet. Chem. 1986, 309, C1–C3.
7. Okamoto, Y.; Madden, P.; Minato, K. J. Nucl. Mater. 2005, 344, 109–114.
8. Okamoto, Y.; Kobayashi, F.; Ogawa, T. J. Alloys Compd. 1998, 271, 355–358.
9. Mech, A.; Karbowick, M.; Lis, T. Polyhedron. 2006, 25, 2083–2092.
10. Bertell, Rosalie. "Gulf War Veterans and Depleted Uranium." May 1999. Available: http://ccnr.org/du_hague.html

External links

• Uranium(III) chloride information at Webelements

Uranium(III) chloride International Bio-Analytical Industries, Inc.

• Depleted Uranium: All the Questions about DU and Gulf War Syndrome are Not Yet Answered