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. It is soluble in water.
Preparation Heating praseodymium and iodine in an inert atmosphere produces praseodymium(III) iodide:
It can also be obtained by heating praseodymium with mercury(II) iodide:
Properties Praseodymium(III) iodide forms green crystals, which are soluble in water. It forms orthorhombic crystals which are hygroscopic. 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, like I3Pr·3N2H4·4H2O which has pale yellow crystals and soluble in methanol, slightly soluble in water, and insoluble in benzene, d20 °C = 2.986 g/cm3.Uchenye zapiski: Serii︠a︡ khimicheskikh nauk (S.M. Kirov adyna Azărbai̐jan Dȯvlăt Universiteti; 1977), trang 37. Truy cập 1 tháng 1 năm 2021. PrI3 forms compounds with urea, like I3Pr·5CO(NH2)2 which has pale green crystals.Russian Journal of Inorganic Chemistry, Tập 18, Phần 2 (British Library Lending Division with the cooperation of the Royal Society of Chemistry, 1973), trang 1655. Truy cập 1 tháng 1 năm 2021. PrI3 forms compounds with thiourea, 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 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. Praseodymium(III) iodide reacts with praseodymium metal at elevated temperatures to form praseodymium diiodide:
2 PrI3 + Pr → 3 PrI2
See also Praseodymium diiodide Praseodymium compounds
References