Praseodymium(III) iodide is an

inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

, consisting of the

rare-earth metal The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...

praseodymium Praseodymium is a chemical element with the Symbol (chemistry), symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered to be one of the rare-earth metals. It is a soft, silvery, malleable and ductile ...

and

iodine Iodine is a chemical element with the symbol I and atomic number 53. The heaviest of the stable halogens, it exists as a semi-lustrous, non-metallic solid at standard conditions that melts to form a deep violet liquid at , and boils to a vi ...

, with the chemical formula PrI₃. It forms green crystals. It is soluble in water.

Preparation

* Heating praseodymium and

in an inert atmosphere produces praseodymium(III) iodide: :

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* It can also be obtained by heating praseodymium with mercury(II) iodide: :

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Properties

Praseodymium(III) iodide forms green crystals, which are soluble in water. It forms

orthorhombic In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a r ...

crystals which are

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...

. It crystallizes in the PuBr₃ type with space group ''Cmcm'' (No. 63) with ''a'' = 4.3281(6) Å, ''b'' = 14.003(6) Å and ''c'' = 9.988(3) Å. It decomposes through an intermediate phase 2 PrI₃·PrOI to a mixture of praseodymium oxyiodide and praseodymium oxide (5 PrOI·Pr₂O₃).

Reactions

* PrI₃ forms compounds with

hydrazine Hydrazine is an inorganic compound with the chemical formula . It is a simple pnictogen hydride, and is a colourless flammable liquid with an ammonia-like odour. Hydrazine is highly toxic unless handled in solution as, for example, hydrazine ...

, like I₃Pr·3N₂H₄·4 H₂O which has pale yellow crystals and soluble in

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical and the simplest aliphatic alcohol, with the formula C H3 O H (a methyl group linked to a hydroxyl group, often abbreviated as MeOH). It is a ...

, slightly soluble in water, and insoluble in

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

, d_{20 °C} = 2.986 g/cm³. * PrI₃ forms compounds with

urea Urea, also known as carbamide, is an organic compound with chemical formula . This amide has two amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest amide of carbamic acid. Urea serves an important r ...

, like I₃Pr·5CO(NH₂)₂ which has pale green crystals. * PrI₃ forms compounds with

thiourea Thiourea () is an organosulfur compound with the formula and the structure . It is structurally similar to urea (), except that the oxygen atom is replaced by a sulfur atom (as implied by the ''thio-'' prefix); however, the properties of urea ...

, like I₃Pr·2CS(NH₂)₂·9H₂O which is a green crystal with d = 2.27 g/cm³. * Praseodymium(III) iodide forms a nonahydrate, PrI₃·9H₂O. It can be obtained by dissolving

praseodymium(III) oxide Praseodymium(III) oxide, praseodymium oxide or praseodymia is the chemical compound composed of praseodymium and oxygen with the formula Pr2O3. It forms light green hexagonal crystals. Praseodymium(III) oxide crystallizes in the manganese(III) oxi ...

in concentrated aqueous

hydroiodic acid Hydroiodic acid (or hydriodic acid) is an aqueous solution of hydrogen iodide (HI). It is a strong acid, one that is ionized completely in an aqueous solution. It is colorless. Concentrated solutions are usually 48% to 57% HI. Reactions Hyd ...

: :Pr₂O₃ + 6 HI + 15H₂O → 2 PrI₃·9H₂O * It adopts the same structure as other light rare earth iodides (La–Ho) and contains a triangular tricapped prismatic nonaaqua ion r(OH₂)₉sup>3+ and

iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine defic ...

counterions. * Praseodymium(III) iodide reacts with praseodymium metal at elevated temperatures to form

praseodymium diiodide Praseodymium diiodide is a chemical compound with the empirical formula of PrI2, consisting of praseodymium and iodine. It is an electride, with the ionic formula of Pr3+(I−)2e−, and therefore not a true praseodymium(II) compound. Preparatio ...

: :2 PrI₃ + Pr → 3 PrI₂

References

{{Lanthanide halides Iodides Lanthanide halides

Preparation

Properties

Reactions

See also

References