Silicon Containing Nine Atom Clusters from Liquid Ammonia Solution: Crystal Structures of the First Protonated Clusters [HSi9]3– and [H2{Si/Ge}9]2–

Abstract

Experiments in liquid ammonia, originally aiming at reactions between Si containing Zintl clusters and transition metal complexes, lead to crystallization of several solvates of nine‐atomic cluster compounds. Starting with the solid Zintl compounds K12Si17, K6Rb6Si17, Rb12Si17, or K12Si8Ge9, the following compounds were crystallized: K4Si9·9 NH3 (1), K4[Si5.6Ge3.4]·9NH3 (2), K0.8Rb3.2Si9·5NH3 (3), K5Si9(OH)·8NH3 (4), K6.5Si9[H0.5N3(Si(NH2)2)3]·4.5NH3 (5), and (Rb[2.2.2]crypt)3Si9·NH3 (6). Most intriguingly, the structural characterization of [K(18‐crown‐6)]3[HSi9]·2NH3·2thf (7) and [K(18‐crown‐6)]2[H2Si4.9Ge4.1]·py (8), succeeded after dilution with tetrahydrofurane and exchange of NH3 by pyridine respectively. The different crystallization products cover bare [E9]4–, purely from Si as well as from mixed Si9–xGex composition, and partially oxidized [Si9]3– clusters, whereas compounds 7 and 8 contain the first protonated nine‐atomic Si clusters, [HSi9]3– and [H2Si4.9Ge4.1]2–. The hydrogen atoms of the protonated clusters in 7 and 8 could be located from difference Fourier maps. Besides an unharmed [Si9]4– cluster compound 5 consists of a cyclotrisilazane ring which arises from an ammonolysis reaction of one of the Si components in the solution.