Siliconoid Expansion by a Single Germanium Atom through Isolated Intermediates

The growth of (semi‐)metal clusters is pivotal for nucleation processes in gaseous and condensed phases. We now report the isolation of intermediates during the expansion of a stable unsaturated silicon cluster (siliconoid) by a single germanium atom through a sequence of substitution, rearrangement and reduction. The reaction of ligato‐lithiated hexasilabenzpolarene LiSi6Tip5 (1Li⋅(thf)2, Tip=2,4,6‐triisopropylphenyl) with GeCl2⋅NHC (NHC=1,3‐diisopropyl‐4,5‐dimethylimidazol‐2‐ylidene) initially yields the product with exohedral germanium(II) functionality, which then inserts into an Si−Si bond of the Si6 scaffold. The concomitant transfer of the chloro functionality from germanium to an adjacent silicon preserves the electron‐precise nature of the formed endohedral germylene. Full incorporation of the germanium heteroatom to the Si6Ge cluster core is finally achieved either by reduction under loss of the coordinating NHC or directly by reaction of 1Li⋅(thf)2 with GeCl2⋅1,4‐dioxane. The expansion of the cluster core of a Si6 siliconoid by a single germanium atom is readily achieved by reaction of a monolithiated Si6 siliconoid with base‐stabilized GeII chlorides. Depending on the stabilizing base (1,4‐dioxane or an NHC), isolable intermediates of the expansion process towards the alleged Si6GeR6 global minimum are obtained and fully characterized (•=silicon).