Praseodymium(III) chloride

Praseodymium(III) chloride
IUPAC name Praseodymium(III) chloride
Other names Praseodymium chloride; praseodymium trichloride
Identifiers
CAS number	10361-79-2 Y
Properties
Molecular formula	PrCl3
Molar mass	247.24 g/mol (anhydrous) 373.77 g/mol (heptahydrate)
Appearance	blue-green solid (anhydrous) light green solid (heptahydrate)
Density	4.02 g/cm3 (anhydrous) 2.250 g/cm3 (heptahydrate)
Melting point	786 °C
Boiling point	1710 °C
Solubility in water	104.0 g/100 ml (13°C)
Structure
Crystal structure	hexagonal (UCl3 type), hP8
Space group	P63/m, No. 176
Coordination geometry	Tricapped trigonal prismatic (nine-coordinate)
Hazards
EU Index	Not listed
Main hazards	Irritant
Related compounds
Other anions	Praseodymium(III) fluoride Praseodymium bromide praseodymium iodide
Other cations	Cerium(III) chloride Neodymium(III) chloride
Y chloride (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Praseodymium(III) chloride is the inorganic compound with the formula PrCl₃. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.

Preparation

Praseodymium(III) chloride is prepared by treating praseodymium metal and hydrogen chloride:^[1][2]

2 Pr + 6 HCl → 2 PrCl₃ + 3 H₂

It is usually purified by vacuum sublimation.^[3]

Hydrated salts of praseodymium(III) chloride can be prpared by treatment of either praseodymium metal or praseodymium(III) carbonate with hydrochloric acid:

Pr₂(CO₃)₃ + 6 HCl + 15 H₂O → 2 [Pr(H₂O)₉]Cl₃ + 3 CO₂

Anhydrous PrCl₃ can be made by thermal dehydration of the hydrate at 400 °C in the presence of ammonium chloride.^[3][4] Alternatively the hydrate can be dehydrated using thionyl chloride.^[3][5]

Reactions

Praseodymium(III) chloride is Lewis acidic, classified as "hard" according to the HSAB concept. Rapid heating of the hydrate may cause small amounts of hydrolysis.^[3] PrCl₃ forms a stable Lewis acid-base complex K₂PrCl₅ by reaction with potassium chloride; this compound shows interesting optical and magnetic properties.^[1]

Aqueous solutions of praseodymium(III) chloride can be used to prepare insoluble praseodymium(III) compounds. For example, praseodymium(III) phosphate and praseodymium(III) fluoride can be prepared by reaction with potassium phosphate and sodium fluoride, respectively:

PrCl₃ + K₃PO₄ → PrPO₄ + 3 KCl

PrCl₃ + 3 NaF → PrF₃ + 3 NaCl

When heated with alkali metal chlorides, it forms a series of ternary (compounds containing three different elements) materials with the formulae MPr₂Cl₇, M₃PrCl₆, M₂PrCl₅, and M₃Pr₂Cl₉ where M = K, Rb, Cs.^[6]

References

1. ^ ^{a b} J. Cybinska, J. Sokolnicki, J. Legendziewicz, G. Meyer Journal of Alloys and Compounds 341, 115-123 (2002).
2. ^ L. F. Druding, J. D. Corbett, J. Am. Chem. Soc. 83, 2462 (1961); J. D. Corbett, Rev. Chim. Minerale 10, 239 (1973)^,
3. ^ ^{a b c d} F. T. Edelmann, P. Poremba, in: Synthetic Methods of Organometallic and Inorganic Chemistry, (W. A. Herrmann, ed.), Vol. 6, Georg Thieme Verlag, Stuttgart, 1997.
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. ^ Gerd Meyer "Ternary Chlorides and Bromides of the Rare-Earth Elements" Inorganic Syntheses, 1990, Volume 30, pp. 72–81. doi:10.1002/9780470132616.ch15

Further reading

1. CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977.
2. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.
3. S. Sugiyama, T. Miyamoto, H. Hayashi, M. Tanaka, J. B. Moffat Journal of Molecular Catalysis A, 118, 129-136 (1997).
4. Druding L. F., Corbett J. D., Ramsey B. N. (1963). "Rare Earth Metal-Metal Halide Systems. VI. Praseodymium Chloride". Inorganic Chemistry 2 (4): 869–871. doi:10.1021/ic50008a055.