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Praseodymium diiodide
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<h2 id="preparation">Preparation</h2> <p>Praseodymium diiodide can be obtained by reacting <a href="/facts/Praseodymium(III)_iodide/ojlLMY7t">praseodymium(III) iodide</a> with metallic praseodymium at 800 °C to 900 °C in an <a href="/facts/Chemically_inert/oglbxzgk">inert</a> atmosphere:<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> Pr + 2 PrI3 → 3 PrI2 <p>It can also be obtained by reacting praseodymium with <a href="/facts/Mercury(II)_iodide/3T73Agxs">mercury(II) iodide</a> where praseodymium displaces <a href="/facts/Mercury_(element)/WlxfoHva">mercury</a>:<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> </p> Pr + HgI2 → PrI2 + Hg <p>Praseodymium diiodide was first obtained by John D. Corbett in 1961.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p> <h2 id="properties">Properties</h2> <p>Praseodymium diiodide is an opaque, bronze-coloured solid with a metallic lustre that is <a href="/facts/Soluble/kLE9h3Jb">soluble</a> in water.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> The lustre and very high conductivity can be explained by the formulation {PrIII,2I−,e−}, with one electron per metal centre delocalised in a conduction band.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>The compound is extremely <a href="/facts/Hygroscopic/1NBGewXv">hygroscopic</a>, and can only be stored and handled under carefully dried inert gas or under a high vacuum. In air it converts into <a href="/facts/Hydrate/dev82l69">hydrates</a> by absorbing moisture, but these are unstable and more or less rapidly transform into oxide iodides with the evolution of hydrogen: </p> 2 PrI2 + 2 H2O → 2 PrOI + H2↑ + 2 HI <p>With <a href="/facts/Water/0lkXnJPK">water</a>, these processes take place much faster.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>Praseodymium diiodide has five <a href="/facts/Crystal_structure/bJ4bCeHd">crystal structures</a>, namely the <a href="/facts/Molybdenum_silicide/lzpJNdxB">MoSi2</a> structure, the hexagonal <a href="/facts/Molybdenum_sulfide/4TRft6Ua">MoS2</a> structure, the trigonal MoS2 structure, the <a href="/facts/Cadmium_chloride/Id9KtSIs">cadmium chloride</a> structure and the <a href="/facts/Spinel/Nb7K5ctV">spinel</a> structure.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> Praseodymium diiodide with the cadmium chloride structure belongs to the <a href="/facts/Trigonal_crystal_system/sSSok8wo">trigonal crystal system</a>, with the space group R3m (No. 166), <a href="/facts/Lattice_parameter/h3gMKk6V">lattice parameters</a> <i>a</i> = 426.5 pm and <i>c</i> = 2247,1 pm; however, the spinel structure of praseodymium diiodide is cubic,<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> with space group F43 (No. 216), and lattice parameter <i>a</i> = 1239.9 pm.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1240–1242. ISBN 978-0-08-037941-8. <a href="978-0-08-037941-8" target="_blank">978-0-08-037941-8</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>hrsg. von Georg Brauer. Unter Mitarb. von M. Baudler (1975). Handbuch der präparativen anorganischen Chemie / 1 (in German). Stuttgart: Enke. p. 1081. ISBN 3-432-02328-6. OCLC 310719485. <a href="3-432-02328-6" target="_blank">3-432-02328-6</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>hrsg. von Georg Brauer. Unter Mitarb. von M. Baudler (1975). Handbuch der präparativen anorganischen Chemie / 1 (in German). Stuttgart: Enke. p. 1081. ISBN 3-432-02328-6. OCLC 310719485. <a href="3-432-02328-6" target="_blank">3-432-02328-6</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Meyer, G.; Naumann, Dieter; Wesemann, Lars (2006). Inorganic chemistry in focus. III. Weinheim: Wiley-VCH. p. 45. ISBN 978-3-527-60993-2. OCLC 86225074. <a href="978-3-527-60993-2" target="_blank">978-3-527-60993-2</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>hrsg. von Georg Brauer. Unter Mitarb. von M. Baudler (1975). Handbuch der präparativen anorganischen Chemie / 1 (in German). Stuttgart: Enke. p. 1081. ISBN 3-432-02328-6. OCLC 310719485. <a href="3-432-02328-6" target="_blank">3-432-02328-6</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1240–1242. ISBN 978-0-08-037941-8. <a href="978-0-08-037941-8" target="_blank">978-0-08-037941-8</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>hrsg. von Georg Brauer. Unter Mitarb. von M. Baudler (1975). Handbuch der präparativen anorganischen Chemie / 1 (in German). Stuttgart: Enke. p. 1081. ISBN 3-432-02328-6. OCLC 310719485. <a href="3-432-02328-6" target="_blank">3-432-02328-6</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Riedel, Erwin; Alsfasser, Ralf (2007). Moderne anorganische Chemie : mit CD-ROM : [133 Tabellen] (in German). Berlin: Gruyter. p. 366. ISBN 978-3-11-019060-1. OCLC 237200027. <a href="978-3-11-019060-1" target="_blank">978-3-11-019060-1</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Warkentin, E.; Bärnighausen, H. (1979). "Die Kristallstruktur von Praseodymdiiodid (Modifikation V)". Z. anorg. allg. Chem. 459: 187–200. doi:10.1002/zaac.19794590120. <a href="/wiki/Zeitschrift_f%C3%BCr_anorganische_und_allgemeine_Chemie" target="_blank">/wiki/Zeitschrift_f%C3%BCr_anorganische_und_allgemeine_Chemie</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Gerlitzki, Niels; Meyer, Gerd; Mudring, Anja-Verena; Corbett, John D. (2004). "Praseodymium diiodide, PrI2, revisited by synthesis, structure determination and theory". J. Alloys Compd. 380 (1–2). Elsevier BV: 211–218. doi:10.1016/j.jallcom.2004.03.046. ISSN 0925-8388. <a href="/wiki/Journal_of_Alloys_and_Compounds" target="_blank">/wiki/Journal_of_Alloys_and_Compounds</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> </ol>