Li18Na2Ge17—A Compound Demonstrating Cation Effects on Cluster Shapes and Crystal Packing in Ternary Zintl Phases

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• 作者：Lavinia M. Scherf ; Michael Zeilinger ; Thomas F. F?ssler
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：February 17, 2014
• 年：2014
• 卷：53
• 期：4
• 页码：2096-2101
• 全文大小：356K
• ISSN：1520-510X

文摘

The novel ternary Zintl phase Liub>18ub>Naub>2ub>Geub>17ub> was synthesized from a stoichiometric melt and characterized crystallographically. It crystallizes in the trigonal space group P31m (No. 157) with a = 17.0905(4) 脜, c = 8.0783(2) 脜, and V = 2043.43(8) 脜up>3up> (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 Geup>4鈥?/sup>, tetrahedra [Geub>4ub>]up>4鈥?/sup>, and truncated, Li-centered tetrahedra [Li@Geub>12ub>]up>11鈥?/sup>, whose hexagonal faces are capped by four Li cations, resulting in the Friauf polyhedra [Li@Liub>4ub>Geub>12ub>]up>7鈥?/sup>. According to the Zintl鈥揔lemm concept, Liub>18ub>Naub>2ub>Geub>17ub> is an electronically balanced Zintl phase, as experimentally verified by its diamagnetism. The compound is structurally related to Liub>7ub>RbGeub>8ub>, which also contains [Geub>4ub>]up>4鈥?/sup> and [Li@Liub>4ub>Geub>12ub>]up>7鈥?/sup> 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.