Overview

Praseodymium(III) chloride (PrCl₃), also known as praseodymium trichloride, is a compound of praseodymium and chlorine. It is a blue-green solid which rapidly absorbs water on exposure to moist air to form a light green heptahydrate.

Chemical properties

Praseodymium(III) chloride can be prepared as a green aqueous solution by reaction of either praseodymium metal or praseodymium(III) carbonate and hydrochloric acid. The anhydrous halide may alternatively be prepared from praseodymium metal and hydrogen chloride^[6].

2 Pr(s) + 6 HCl(aq) → 2 PrCl₃(aq) + 3 H₂(g)

Pr₂(CO₃)₃ (s) + 6 HCl(aq) → 2 PrCl₃(aq) + 3 CO₂(g) + 3 H₂O(l)

Praseodymium(III) chloride is a moderately strong Lewis acid, which ranks as "hard" according to the Hard-Soft Acid-Base theory . Rapid heating of the hydrate may cause small amounts of hydrolysis ^[1].

Preparation

Aqueous solutions of praseodymium(III) chloride can be used to prepare insoluble praseodymium(III) compounds, for example praseodymium(III) phosphate or praseodymium(III) fluoride:

PrCl₃(aq) + K₃PO₄ (aq) → PrPO₄(s) + 3 KCl(aq)

PrCl_3(aq)aq + 3 NaF(aq) → PrF₃(s) + 3 NaCl(aq)

Anhydrous PrCl₃ can be made by dehydration of the hydrate either by slowly heating to 400 °C with 4-6 equivalents of ammonium chloride under high vacuum^[1],[4], or by heating with an excess of thionyl chloride for four hours^[1],[5]. The anhydrous halide may alternatively be prepared from praseodymium metal and hydrogen chloride ^[6]. It is usually purified by high temperature sublimation under high vacuum. ^[1]

Uses

There are no major uses for praseodymium(III) chloride, though it can be used as a starting point for the preparation of other praseodymium salts.

Precautions

Praseodymium compounds are of low to moderate [[toxicity], although their toxicity has not been investigated in detail. Wear gloves and goggles.

Suppliers/Manufacturers

GFS: http://www.gfschemicals.com/productcatalog/Rare_Earth_Compounds_PT.asp

Aldrich: http://www.sigmaaldrich.com

Strem: http://www.strem.com/code/index.ghc

Alfa: http://www.alfa.com/alf/index.htm

In the US, several of these suppliers also distribute through VWR: http://www.vwr.com/index.htm or Fisher: https://www1.fishersci.com/index.jsp

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References

1. F. T. Edelmann, P. Poremba, in: Synthetic Methods of Organometallic and Inorganic Chemistry, (W. A. Herrmann, ed.), Vol. 6, Georg Thieme Verlag, Stuttgart, 1997.
2. CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977.
3. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.
4. M. D. Taylor, P. C. Carter, J. Inorg. Nucl. Chem. 24, 387 (1962); J. Kutscher, A. Schneider, Inorg. Nucl. Chem. Lett. 7, 815 (1971).
5. J. H. Freeman, M. L. Smith, J. Inorg. Nucl. Chem. 7, 224 (1958).
6. L. F. Druding, J. D. Corbett, J. Am. Chem. Soc. 83, 2462 (1961); J. D. Corbett, Rev. Chim. Minerale 10, 239 (1973).