Soluble Zintl Phases A(14)ZnGe(16) (A=K, Rb) Featuring [(eta(3)-Ge-4) Zn(eta(2)-Ge-4)](6-) and [Ge-4](4-) Clusters and the Isolation of [(MesCu)(2)(eta(3),eta(3)-Ge-4)](4-): The Missing Link in the Solution Chemistry of Tetrahedral Group 14 Element Zintl Clusters

Saskia Stegmaier, Markus Waibel, Alexander Henze, Laura-Alice Jantke, Antti J. Karttunen, Thomas F. Faessler*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


The number of Zintl phases containing polyhedral clusters of tetrel elements that are accessible for chemical reactions of the main-group element clusters is rather limited. The synthesis and structural characterization of two novel ternary intermetallic phases A(14)ZnGe(16) (A = K, Rb) are presented, and their chemical reactivity is investigated. The compounds can be rationalized as Zintl phases with 14 alkali metal cations A(+) (A = K, Rb), two tetrahedral [Ge-4](4-) Zintl anions, and one anionic heterometallic [(Ge-4)Zn(Ge-4)](6-) cluster per formula unit. The Zn-Ge cluster comprises two (Ge4) tetrahedra which are linked by a Zn atom, with one (Ge-4) tetrahedron coordinating with a triangular face (eta(3)) and the other one with an edge (eta(2)). [(eta(3)-Ge-4)Zn(eta(2)-Ge-4)](6-) is a new isomer of the [(Ge-4)Zn(Ge-4)](6-) anion in Cs6ZnGe8. The phases dissolve in liquid ammonia and thus represent rare examples of soluble Zintl compounds with deltahedral units of group 14 element atoms. Compounds with tetrahedral [E-4](4-) species have previously been isolated from solution for E = Si, Sn, and Pb, and the current investigation provides the "missing link" for E = Ge. Reaction of an ammonia solution of K14ZnGe16 with MesCu (Mes = 2,4,6-(CH3)(3)C6H2) in the presence of [18]-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) yielded crystals of the salt [K([18]-crown-6)](2)K-2[(MesCu)(2)Ge-4](NH3)(7.5) with the polyanion [(MesCu)(2)Ge-4](4-). This MesCu-stabilized tetrahedral [Ge-4](4-) cluster also completes the series of [(MesCu)(2)Si4-xGex](4-) clusters, which have previously been isolated from solution for x = 0 and 0.7, as the end member with x = 4. The electronic structures of [(Ge-4)Zn(Ge-4)](6-) and [(MesCu)(2)Ge-4](4-) were investigated in terms of a molecular orbital description and analyses of the electron localization functions. The results are compared with band structure calculations for the A(14)ZnGe(16) phases (A = K, Rb).

Original languageEnglish
Pages (from-to)14450-14460
Number of pages11
JournalJournal of the American Chemical Society
Issue number35
Publication statusPublished - 5 Sep 2012
MoE publication typeA1 Journal article-refereed


  • IONS
  • CS
  • GOLD
  • NMR

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