Challenges in chemical synthesis at the border of solution-based and solid-state chemistry—Synthesis and structure of [CH₃CH₂Ge₉{Si(SiMe₃)₃}]²⁻

Polyanionic [Ge₉]^4– clusters are accessible in good yields by a solid-state reaction of the elements Ge and K. The nine-atom deltahedral germanium clusters are transformed to silylated species, which in a subsequent reaction allow for addition of an organic moiety. We present a synthetic method for a stepwise ligand exchange reaction at a Zintl ion. Herein, we functionalized the [Ge₉{Si(SiMe₃)₃}₂]²⁻ cluster with an ethyl group by a reaction with bromoethane. The obtained anion [CH₃CH₂Ge₉{Si(SiMe₃)₃}₂]⁻ was characterized by NMR spectroscopy and mass spectrometry. After addition of 2,2,2-crypt an abstraction of one silyl ligand was observed resulting in the crystallization of [K(2,2,2-crypt)]₂[CH₃CH₂Ge₉{Si(SiMe₃)₃}] representing the first monosilylated Ge₉ Zintl cluster, which carries an additional ethyl group. The latter compound was characterized by single crystal X-ray crystallography, NMR spectroscopy, and elemental analysis.