Preparation and crystal structure of the ternary uranium rare Earth antimonides (U(2/3)R(1/3))Sb(2) and (U(1/2)R(1/2))(3)Sb(7) with mixed U/R occupancy of the metal sites and a variety of antimony polyanions.
Preparation and crystal structure of the ternary uranium rare Earth antimonides (U(2/3)R(1/3))Sb(2) and (U(1/2)R(1/2))(3)Sb(7) with mixed U/R occupancy of the metal sites and a variety of antimony polyanions.
复制标题
三元铀稀土锑化物(U(2/3)R(1/3))Sb(2)和(U(1/2)R(1/2))(3)Sb(7)的制备及晶体结构
作者：
T. Schmidt;W. Jeitschko
三元锑化物 (U(2/3)R(1/3))Sb(2) (R = Y, Ce-Nd, Sm, Gd-Tm) 和 (U(1/2)R(1/2))(3)Sb(7) (R = Y, Gd-Ho) 是通过铀锑化物 USb(2) 与相应的稀土锑化物 RSb(2) 和过量元素反应制备的高温下的锑。同型系列(U(2/3)R(1/3))Sb(2)的晶体结构已从(U(0.675(9))Gd(0.325(9)))Sb(2)的单晶X射线数据确定。它与 PbCl(2) 是同型的：Pnma，Z = 4，a = 754.6(1)，b = 419.6(1)，c = 1025.7(3) pm。其他系列的化合物结晶出新的结构类型，已确定为 (U(0.49(1))Ho(0.51(1)))(3)Sb(7): Immm, Z = 4, a = 410.1(1), b = 1447.7(3), c = 1821.2(5) pm。在这两种结构中，金属位置具有混合占据和高配位数。两种结构均含有大量弱Sb-Sb键，从而在(U(2/3)Gd(1/3))Sb(2)结构中形成锑原子带，在(U(1/2)Ho(1/2))(3)Sb(7)结构中形成锑原子链和三维无限网络。基于键长键强度考虑对锑聚阴离子内的Sb-Sb键进行的分析表明，这些化合物中的铀原子具有混合或中间的+3/+4价。 (U(1/2)Ho(1/2))(3)Sb(7)结构可以被认为是Ce(6)MnSb(15)结构的缺陷变体。
The ternary antimonides (U(2/3)R(1/3))Sb(2) (R = Y, Ce-Nd, Sm, Gd-Tm) and (U(1/2)R(1/2))(3)Sb(7) (R = Y, Gd-Ho) have been prepared by reaction of the uranium antimonide USb(2) with the corresponding rare earth antimonides RSb(2) and an excess of elemental antimony at high temperatures. The crystal structure of the isotypic series (U(2/3)R(1/3))Sb(2) has been determined from single-crystal X-ray data of (U(0.675(9))Gd(0.325(9)))Sb(2). It is isotypic with PbCl(2): 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 new structure type, which has been determined for (U(0.49(1))Ho(0.51(1)))(3)Sb(7): 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(2/3)Gd(1/3))Sb(2) and a chain and a three-dimensionally infinite network of antimony atoms in the structure of (U(1/2)Ho(1/2))(3)Sb(7). Analyses of the Sb-Sb bonding within the antimony polyanions on the basis of bond-length bond-strength considerations indicate that the uranium atoms have mixed or intermediate +3/+4 valence in these compounds. The structure of (U(1/2)Ho(1/2))(3)Sb(7) may be considered as a defect variant of the structure of Ce(6)MnSb(15).