Preparation and Crystal Structure of the Ternary Uranium Rare Earth Antimonides (U2/3R1/3)Sb2 and (U1/2R1/2)3<

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• 作者：Tobias Schmidt and Wolfgang Jeitschko
• 刊名：Inorganic Chemistry
• 出版年：2001
• 出版时间：December 3, 2001
• 年：2001
• 卷：40
• 期：25
• 页码：6356 - 6361
• 全文大小：114K
• 年卷期：v.40,no.25(December 3, 2001)
• ISSN：1520-510X

文摘

The ternary antimonides (U_2/3R_1/3)Sb₂ (R = Y, Ce-Nd, Sm, Gd-Tm) and (U_1/2R_1/2)₃Sb₇ (R = Y, Gd-Ho) havebeen prepared by reaction of the uranium antimonide USb₂ with the corresponding rare earth antimonides RSb₂and an excess of elemental antimony at high temperatures. The crystal structure of the isotypic series (U_2/3R_1/3)Sb₂has been determined from single-crystal X-ray data of (U_0.675(9)Gd_0.325(9))Sb₂. It is isotypic with PbCl₂: Pnma, Z= 4, a = 754.6(1), b = 419.6(1), c = 1025.7(3) pm. The compounds of the other series crystallize with a newstructure type, which has been determined for (U_0.49(1)Ho_0.51(1))₃Sb₇: Immm, Z = 4, a = 410.1(1), b = 1447.7(3),c = 1821.2(5) pm. In both structures, the metal positions have mixed occupancy and high coordination numbers.Both structures contain numerous weak Sb-Sb bonds, thus forming a band of antimony atoms in the structure of(U_2/3Gd_1/3)Sb₂ and a chain and a three-dimensionally infinite network of antimony atoms in the structure of(U_1/2Ho_1/2)₃Sb₇. Analyses of the Sb-Sb bonding within the antimony polyanions on the basis of bond-lengthbond-strength considerations indicate that the uranium atoms have mixed or intermediate +3/+4 valence in thesecompounds. The structure of (U_1/2Ho_1/2)₃Sb₇ may be considered as a defect variant of the structure of Ce₆MnSb₁₅.