Scherf Lavinia M, Zeilinger Michael, Fässler Thomas F
Department Chemie, Technische Universität München , Lichtenbergstraße 4, 85747 Garching b. München, Germany.
Inorg Chem. 2014 Feb 17;53(4):2096-101. doi: 10.1021/ic4027046. Epub 2014 Jan 31.
The novel ternary Zintl phase Li18Na2Ge17 was synthesized from a stoichiometric melt and characterized crystallographically. It crystallizes in the trigonal space group P31m (No. 157) with a = 17.0905(4) Å, c = 8.0783(2) Å, and V = 2043.43(8) Å(3) (final R indices R1 = 0.0212 and wR2 = 0.0420 for all data). The structure contains three different Zintl anions in a 1:1:1 ratio: isolated anions Ge(4-), tetrahedra Ge4, and truncated, Li-centered tetrahedra Li@Ge12, whose hexagonal faces are capped by four Li cations, resulting in the Friauf polyhedra Li@Li4Ge12. According to the Zintl-Klemm concept, Li18Na2Ge17 is an electronically balanced Zintl phase, as experimentally verified by its diamagnetism. The compound is structurally related to Li7RbGe8, which also contains Ge4 and Li@Li4Ge12 in its anionic substructure. However, exchanging the heavier alkali metal cation Rb for Na in the mixed-cation germanides leads to drastic changes in stoichiometry and crystal packing, demonstrating the great effects that cations exert on such Zintl phases through optimized cluster sheathing and space filling.
新型三元津特耳相Li18Na2Ge17由化学计量熔体合成，并进行了晶体学表征。它结晶于三方空间群P31m（编号157），a = 17.0905(4) Å，c = 8.0783(2) Å，V = 2043.43(8) ų（所有数据的最终R指标R1 = 0.0212，wR2 = 0.0420）。该结构包含三种比例为1:1:1的不同津特耳阴离子：孤立阴离子Ge⁴⁻、四面体[Ge4]⁴⁻以及截顶的、以锂为中心的四面体[Li@Ge12]¹¹⁻，其六边形面被四个锂阳离子覆盖，形成弗里奥夫多面体[Li@Li4Ge12]⁷⁻。根据津特耳 - 克莱姆概念，Li18Na2Ge17是电子平衡的津特耳相，其抗磁性已通过实验验证。该化合物在结构上与Li7RbGe8相关，Li7RbGe8的阴离子亚结构中也含有[Ge4]⁴⁻和[Li@Li4Ge12]⁷⁻。然而，在混合阳离子锗化物中用较重的碱金属阳离子Rb替换Na会导致化学计量和晶体堆积发生剧烈变化，这表明阳离子通过优化簇包覆和空间填充对此类津特耳相产生了巨大影响。
