Zintl Phases K_4–xNa_xSi₄ (1 ≤ x ≤ 2.2) and K₇NaSi₈: Synthesis, Crystal Structures, and Solid‐State NMR Spectroscopic Investigations

Abstract

The Zintl phases K4–xNaxSi4 (1 ≤ x ≤ 2.2) and K7NaSi8 are the first representatives of the K–Na–Si system, and both contain tetrahedral [Si4]4– clusters and a charge‐balancing number of K+ and Na+ cations. All phases of K4–xNaxSi4 (1 ≤ x ≤ 2.2) crystallize in a new structure type with space group P21/n, as determined by single‐crystal X‐ray diffraction analysis of the parent phase K3NaSi4. Rietveld refinement of the X‐ray diffraction data showed that the solid solutions follow Vegard's rule. K7NaSi8 can only be synthesized by diffusion‐controlled reaction of binary precursors and is isostructural with known A7A′T8 (A = Na–Cs; A′ = Li, Na; T = Si, Ge) phases. A combination of solid‐state NMR investigations and quantum mechanical calculations served to show the anisotropic chemical bonding behavior of all the atoms in K7NaSi8, which is additionally compared with the related phases A7NaSi8 (A = Rb, Cs).

Synthesis and characterization of ternary trielides Na7KTr4 [Tr=In or Tl] including [Tr4]8− Tetrahedra

“…Concerning the combination of alkali metals and group 14 and 15 elements, a variety of isolated clusters can be found, [14,15] which can be described using the (8‐ N ) rule [16–18] . According to the pseudo element concept, [19] tetrahedral [ Tt 4 ] 4− clusters are reported in binary materials A 12 Tt 17 and A 4 Tt 4 ( A =Na−Cs, Tt =Si−Pb) [20–32] . The combination of different alkali metals allowed for the observation of new structure types, e. g. Rb 7 Na(Ge 4 ) 2 , [32] Cs 2 Na 2 Ge 4 [27] and Li 18 Na 2 Ge 17 [33] .…”

“…The combination of different alkali metals allowed for the observation of new structure types, e. g. Rb 7 Na(Ge 4 ) 2 , [32] Cs 2 Na 2 Ge 4 [27] and Li 18 Na 2 Ge 17 [33] . While these materials show that ordering can be observed, the solid solution of K 4‐x Na x Si 4 proves that mixed alkali metal sites are also possible [23] …”

“…[16][17][18] According to the pseudo element concept, [19] tetrahedral [Tt 4 ] 4À clusters are reported in binary materials A 12 Tt 17 and A 4 Tt 4 (A = NaÀ Cs, Tt = SiÀ Pb). [20][21][22][23][24][25][26][27][28][29][30][31][32] The combination of different alkali metals allowed for the observation of new structure types, e. g. Rb 7 Na(Ge 4 ) 2 , [32] Cs 2 Na 2 Ge 4 [27] and Li 18 Na 2 Ge 17 . [33] While these materials show that ordering can be observed, the solid solution of K 4-x Na x Si 4 proves that mixed alkali metal sites are also possible.…”

Fellows der Electrochemical Society: C. Amatore, K. Amine, P. Atanassov, C. P. Grey, Y. Shao‐Horn und N. Wu / Priestley‐Medaille: G. Richmond / Förderungspreis der Stadt Wien: N. Maulide

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Clare P. Grey (University of Cambridge) wurde in dieser Rubrik vorgestellt, als ihr der Arfvedson‐Schlenk‐Preis verliehen worden war . Sie ist Coautorin einer Veröffentlichung im European Journal of Inorganic Chemistry über Zintl‐Phasen …”

Si44– in Solution – First Solvate Crystal Structure of the Ligand‐free Tetrasilicide Tetraanion in Rb1.2K2.8Si4·7NH3

“…Homoatomic polyanions in solution, so called Zintl anions, represent a very interesting class of compounds as they can be seen as naked anionic building blocks for the elements . For group 14 elements, these polyanions can be generated from binary or ternary phases, which contain tetrahedral [ E 4 ] 4– ions in A 4 E 4 ( A = Na ‐ Cs, E = Si – Sn), nine‐atom clusters [ E 9 ] 4– in A 4 E 9 ( A = K – Cs, E = Ge – Pb), and both kinds of clusters with the ratio of 2:1 in A 12 E 17 ( A = K – Cs, E = Si – Sn) , . The last two mentioned phases can be readily dissolved in liquid ammonia and in the case of A 4 E 9 additionally in ethylendiamine and N,N ‐dimethylformamide .…”