Endohedrally Filled [Ni@Sn_9]~(4-) and [Co@Sn_9]~(5-) Clusters in the Neat Solids Na_(12)Ni_(1-x)Sn_(17) and K_(13-x)Co_(1-x)Sn_(17): Crystal Structure and ~(119)Sn Solid-State NMR Spectroscopy

摘要

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 Na_(12)Ni_(1-x)Sn_(17) and K_(13-x)Co_(1-x)Sn_(17), containing endohedrally filled intermetalloid clusters [Ni@Sn_9]~(4-) or [Co@Sn_9]~(5-) beside [Sn_4]~(4-), are obtained from high-temperature reactions. The arrangement of [Ni@Sn_9]~(4-) or [Co@Sn_9]~(5-) and [Sn_4]~(4-) clusters, which are present in the ratio 1:2, can be regarded as a hierarchical replacement variant of the hexagonal Laves phase MgZn_2 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 {Sn_9} cages correlates strongly with the number of K vacancies in K_(13-x)Co_(1-x)Sn_(17) and K_(5-x)Co_(1-x)Sn_9, and consequently, all compounds correspond to diamagnetic valence compounds. Owing to their diamagnetism, K_(13-x)Co_(1-x)Sn_(17), and K_(5-x)Co_(1-x)Sn_9, as well as the d-block metal free binary compounds K_(12)Sn_(17) and K_4Sn_9, were characterized for the first time by ~(119)Sn solid-state NMR spectroscopy.