Praseodymium(III) iodide

Names
Other names Praseodymium triiodide
Identifiers
CAS Number	13813-23-5
3D model (JSmol)	Interactive image
ChemSpider	75566
ECHA InfoCard	100.034.046
EC Number	237-466-1
PubChem CID	83744
CompTox Dashboard (EPA)	DTXSID5065641
InChI InChI=1S/3HI.Pr/h3*1H;/q;;;+3/p-3 Key: PVEVRIVGNKNWML-UHFFFAOYSA-K
SMILES I[Pr](I)I
Properties
Chemical formula	PrI3
Molar mass	521.619 g/mol 683.75652 g/mol (nonahydrate)
Appearance	hygroscopic green crystals
Density	5.8 g/cm3[1]
Melting point	738 °C (1,360 °F; 1,011 K)[1]
Boiling point	1,380 °C (2,520 °F; 1,650 K)
Solubility in water	213.9 g/100 mL[2]
Hazards
GHS labelling:[3]
Pictograms
Signal word	Danger
Hazard statements	H317, H360
Precautionary statements	P203, P261, P272, P280, P302+P352, P318, P321, P333+P313, P362+P364, P405, P501
Related compounds
Other anions	Praseodymium(III) fluoride Praseodymium(III) chloride Praseodymium(III) bromide
Other cations	Cerium(III) iodide Neodymium(III) iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Praseodymium(III) iodide is an inorganic salt, consisting of the rare-earth metal praseodymium and iodine, with the chemical formula PrI₃. It forms green crystals.^[4] It is soluble in water.^[5]

Preparation

• Heating praseodymium and iodine in an inert atmosphere produces praseodymium(III) iodide:^[1]

${\displaystyle {\mathsf {2Pr+3I_{2}\ \xrightarrow {T} \ 2PrI_{3))))$

• It can also be obtained by heating praseodymium with mercury(II) iodide:^[6]

${\displaystyle {\mathsf {2Pr+3HgI_{2}\ \xrightarrow {T} \ 2PrI_{3}+3Hg))}$

Properties

Praseodymium(III) iodide forms green crystals, which are soluble in water.^[5] It forms orthorhombic crystals which are hygroscopic.^[1] It crystallizes in the PuBr₃ type^[6][7] with space group Cmcm (No. 63) with a = 4.3281(6) Å, b = 14.003(6) Å and c = 9.988(3) Å.^[8] It decomposes through an intermediate phase 2 PrI₃·PrOI to a mixture of praseodymium oxyiodide and praseodymium oxide (5 PrOI·Pr₂O₃).^[9]

Reactions

• PrI₃ forms compounds with hydrazine, like I₃Pr·3N₂H₄·4H₂O which has pale yellow crystals and soluble in methanol, slightly soluble in water, and insoluble in benzene, d_{20 °C} = 2.986 g/cm³.^[10]

• PrI₃ forms compounds with urea, like I₃Pr·5CO(NH₂)₂ which has pale green crystals.^[11]

• PrI₃ forms compounds with thiourea, like I₃Pr·2CS(NH₂)₂·9H₂O which is a green crystal with d = 2.27 g/cm³.^[5][12]

• Praseodymium(III) iodide forms a nonahydrate, PrI₃·9H₂O. It can be obtained by dissolving praseodymium(III) oxide in concentrated aqueous hydroiodic acid:

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 [Pr(OH₂)₉]³⁺ and iodide counterions.^[4]

• Praseodymium(III) iodide reacts with praseodymium metal at elevated temperatures to form praseodymium diiodide:^[13]

2 PrI₃ + Pr → 3 PrI₂