Controlled cluster expansion at a Zintl cluster surface

Reaction of the tris‐hypersilyl nonagermanide Zintl cluster salt, K[Ge9(Hyp)3] (Hyp=Si(SiMe3)3) with [Rh(η2,η2‐L)Cl]2 (L=1,5‐cyclooctadiene, COD; norbornadiene, NBD) afforded eleven‐ and twelve‐vertex homo‐multimetallic clusters by cluster core expansion. Using a stepwise procedure, starting from the Zintl cluster [Rh(COD){Ge9(Hyp)3}] and [Ir(COD)Cl]2, this methodology was expanded for the synthesis of eleven‐vertex hetero‐multimetallic clusters. A mechanism for the formation of these first examples of closo eleven‐vertex Zintl clusters is proposed, informed by density functional theory calculations. The stepwise growth of eleven‐ and twelve‐vertex multimetallic clusters from a ten‐atom precursor is demonstrated. These rare examples of closo‐ to closo‐ cluster expansion reactions offer insight into the mechanisms by which Zintl clusters assemble in solution. The resultant clusters possess exo‐bonds to chlorine atoms that may allow for post‐synthetic functionalization and their incorporation into materials.