Heating praseodymium and iodine in an inert atmosphere produces praseodymium(III) iodide:[1]
It can also be obtained by heating praseodymium with mercury(II) iodide:[6]
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, d20 °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]
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]
^Wells, A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford University Press. p. 421. ISBN978-0-19-965763-6.
^E. Warkentin, H. Bärnighausen (1979), "Die Kristallstruktur von Praseodymdiiodid (Modifikation V)", Zeitschrift für anorganische und allgemeine Chemie (in German), vol. 459, no. 1, pp. 187–200, doi:10.1002/zaac.19794590120
