Endohedrally Filled [Ni@Sn₉]⁴⁻ and [Co@Sn₉]⁵⁻ Clusters in the Neat Solids Na₁₂Ni_1−<i>x</i>Sn₁₇ and K_{13−<i>x</i>}Co_1−<i>x</i>Sn₁₇: Crystal Structure and ¹¹⁹Sn Solid‐State NMR Spectroscopy

Abstract

A systematic approach to the formation of endohedrally filled atom clusters by a high-temperature route instead of the more frequent multistep syntheses in solution is presented. Zintl phases Na12Ni(1-x)Sn17 and K(13-x)Co(1-x)Sn17, containing endohedrally filled intermetalloid clusters [Ni@Sn9](4-) or [Co@Sn9](5-) beside [Sn4](4-), are obtained from high-temperature reactions. The arrangement of [Ni@Sn9](4-) or [Co@Sn9](5-) and [Sn4](4-) clusters, which are present in the ratio 1:2, can be regarded as a hierarchical replacement variant of the hexagonal Laves phase MgZn2 on the Mg and Zn positions, respectively. The alkali-metal positions are considered for the first time in the hierarchical relationship, which leads to a comprehensive topological parallel and a better understanding of the composition of these compounds. The positions of the alkali-metal atoms in the title compounds are related to the known inclusion of hydrogen atoms in the voids of Laves phases. The inclusion of Co atoms in the {Sn9} cages correlates strongly with the number of K vacancies in K(13-x)Co(1-x)Sn17 and K(5-x)Co(1-x)Sn9, and consequently, all compounds correspond to diamagnetic valence compounds. Owing to their diamagnetism, K(13-x)Co(1-x)Sn17, and K(5-x)Co(1-x)Sn9, as well as the d-block metal free binary compounds K12Sn17 and K4Sn9, were characterized for the first time by (119)Sn solid-state NMR spectroscopy.