Preparation, Crystal Structures, and Properties of Rhenates with Multiple Re–Re Bonds: Ln2ReO5 (Ln=Sm, Eu, Gd), Ln3Re2O9 (Ln=Pr, Nd, Sm), and Ln4Re6O19 (Ln=La–Nd)

✍ Scribed by Wolfgang Jeitschko; Dieter H Heumannskämper; Marietta S Schriewer-Pöttgen; Ute Ch Rodewald

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 268 KB
• Volume: 147
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8237

✦ Synopsis

Most of the title compounds were prepared by reaction of the rare-earth metaperrhenates Ln(ReO 4 ) 3 with the rare-earth metals in sealed silica tubes. Nd 4 Re 6 O 19 was obtained by reaction of the intermetallic compound NdRe 2 with the metaperrhenate Nd(ReO 4 ) 3 . The compounds Ln 2 ReO 5 crystallize with a tetragonal structure (P4/n, Z ‫؍‬ 4), which was determined from fourcircle X-ray di4ractometer data of twinned crystals of Eu 2 ReO 5 [a ‫؍‬ 861.0(4) pm, c ‫؍‬ 574.3(3) pm] and re5ned for Gd 2 ReO 5 [a ‫؍‬ 858.8(4) pm, c ‫؍‬ 569.6(2) pm]. The compounds Ln 3 Re 2 O 9 are isotypic with La 3 Re 2 O 9 , however, with somewhat di4ering oxygen coordination of the rare-earth atoms, as was shown by a structure re5nement from single-crystal data of Sm 3 Re 2 O 9 [P1 , a ‫؍‬ 551.8(1) pm, b ‫؍‬ 678.8(2) pm, c ‫؍‬ 1086.7(3) pm, ‫؍‬ 76.57(1)3, ‫؍‬ 75.56(2)3, ‫؍‬ 68.66(1)3]. The rhenates Ln 4 Re 6 O 19 have a structure 5rst determined for La 4 Re 6 O 19 . The rhenium atoms in the compounds Ln 2 ReO 5 , with the oxidation number ؉4, are paired with a formal Re+Re triple bond (225 pm) in a square-antiprismatic oxygen coordination (Re 2 O 8 ). In Sm 3 Re 2 O 9 two kinds of Re 2 pairs are present. The Re(IV) pairs with a formal triple bond have again a Re+Re distance of 225 pm. They are situated in a tetragonal prism of oxygen atoms. The other rhenium atoms, with oxidation number ؉5, have octahedral oxygen coordination. They form pairs via a common edge of their oxygen octahedra with a formal double bond of 242 pm. The magnetic properties of these compounds indicate that the rhenium atoms do not carry any substantial magnetic moments. The crystal structures of the reduced oxorhenates of the rare-earth elements are brie6y reviewed. The Re+Re bond lengths correlate with the formal bond order deduced from the oxidation states.