Nonagermanide Zintl Clusters with Mg²⁺ Counter Ions

Ion exchange processes are rarely investigated with respect to tetrel element Zintl clusters. We now discovered that the addition of Mg complexes to nonagermanide anions comprising K⁺ counter cations results in an exchange of the alkali ions by alkaline earth cations. Upon stirring K[Ge₉{Si(TMS)₃}₃] (TMS=trimethylsilyl) and Mg(NacNac^Mes)I (NacNac^Mes=N,N’-bis(2,4,6-trimethylphenyl)-β-diketiminate) in MeCN the product [Mg(NacNac^Mes)(MeCN)₄][Ge₉{Si(TMS)₃}₃]⋅ MeCN is formed. Reactions of Mg(NacNac^Mes)I with K₄Ge₉ in liquid ammonia as a solvent yielded [K[2.2.2]crypt]₄[Mg(NacNac^Mes)(NH₃)₄]₂[Ge₉−Ge₉] ⋅ 32.58 NH₃ featuring a mixed alkali/alkaline earth metal cationic sphere and an oxidative coupling of the [Ge₉]⁴⁻ clusters. From comparable reactions of [Mg(NacNac^Mes)]₂ with K₄Ge₉ or K₁₂Ge₁₇ in liquid ammonia crystals of [K[2.2.2]crypt][NacNac^Mes] ⋅ NH₃ and [K(18-crown-6)][NacNac^Mes] ⋅ 3 NH₃, respectively, were isolated. All compounds were characterized by means of single crystal structure determination.