Praseodymium(III) chloride
Encyclopedia
Praseodymium chloride is the inorganic compound
with the formula
Pr
Cl
3. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.
:
It is usually purified by vacuum sublimation.
Hydrated salts of praseodymium(III) chloride can be prpared by treatment of either praseodymium metal or praseodymium(III) carbonate with hydrochloric acid
:
Anhydrous PrCl3 can be made by thermal dehydration of the hydrate at 400 °C in the presence of ammonium chloride
. Alternatively the hydrate can be dehydrated using thionyl chloride
.
ic, classified as "hard" according to the HSAB concept. Rapid heating of the hydrate
may cause small amounts of hydrolysis
. PrCl3 forms a stable Lewis acid-base complex K2PrCl5 by reaction with potassium chloride
; this compound shows interesting optical
and magnetic
properties.
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:
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.
Inorganic compound
Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Pr
Praseodymium
Praseodymium is a chemical element that has the symbol Pr and atomic number 59. Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group. It is too reactive to be found in native form, and when artificially prepared, it slowly develops a green oxide coating.The element...
Cl
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
3. 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 chlorideHydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
:
- 2 Pr + 6 HCl → 2 PrCl3 + 3 H2
It is usually purified by vacuum sublimation.
Hydrated salts of praseodymium(III) chloride can be prpared by treatment of either praseodymium metal or praseodymium(III) carbonate with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric 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
Ammonium chloride
Ammonium chloride NH4Cl is an inorganic compound with the formula NH4Cl. It is a white crystalline salt that is highly soluble in water. Solutions of ammonium chloride are mildly acidic. Sal ammoniac is a name of natural, mineralogical form of ammonium chloride...
. Alternatively the hydrate can be dehydrated using thionyl chloride
Thionyl chloride
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...
.
Reactions
Praseodymium(III) chloride is Lewis acidLewis acid
]The term Lewis acid refers to a definition of acid published by Gilbert N. Lewis in 1923, specifically: An acid substance is one which can employ a lone pair from another molecule in completing the stable group of one of its own atoms. Thus, H+ is a Lewis acid, since it can accept a lone pair,...
ic, classified as "hard" according to the HSAB concept. Rapid heating of the hydrate
Hydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
may cause small amounts of hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
. PrCl3 forms a stable Lewis acid-base complex K2PrCl5 by reaction with potassium chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
; this compound shows interesting optical
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
and magnetic
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
properties.
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
Potassium phosphate
Potassium phosphate is a generic term for the salts of potassium and phosphate ions including:* Monopotassium phosphate * Dipotassium phosphate * Tripotassium phosphate...
and sodium fluoride
Sodium fluoride
Sodium fluoride is an inorganic chemical compound with the formula NaF. A colorless solid, it is a source of the fluoride ion in diverse applications. Sodium fluoride is less expensive and less hygroscopic than the related salt potassium 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.
Further reading
- CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977.
- N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984.
- S. Sugiyama, T. Miyamoto, H. Hayashi, M. Tanaka, J. B. Moffat Journal of Molecular Catalysis A, 118, 129-136 (1997).