Reactivity and Controlled Redox Reactions of Salt‐like Intermetallic Compounds in Imidazolium‐Based Ionic Liquids

Substituted imidazolium ionic liquids (ILs) were investigated for their reactivity towards Na(12)Ge(17) as a model system containing redox‐sensitive Zintl cluster anions. The ILs proved widely inert for imidazolium cations with a 1,2,3‐trisubstitution at least by alkyl groups, and for the anion bis(trifluoromethylsulfonyl)azanide (TFSI). A minute conversion of Na(12)Ge(17) observed on long‐time contact with such ILs was not caused by dissolution of the salt‐like compound, and did thus not provide dissolved Ge clusters. Rather, a cation exchange led to the transfer of Na(+) ions into solution. In contrast, by using benzophenone as an oxidizer, heterogeneous redox reactions of Na(12)Ge(17) were initiated, transferring a considerable part of Na(+) into solution. At optimized conditions, an X‐ray amorphous product NaGe(6.25) was obtained, which was thermally convertible to the crystalline type‐II clathrate Na(24–δ)Ge(136) with almost completely Na‐filled polyhedral cages, and α‐Ge. The presented method thus provides unexpected access to Na(24–δ)Ge(136) in bulk quantities.