Keplerate Ag₁₉₂ Cluster with 6 Silver and 14 Chalcogenide Octahedral and Tetrahedral Shells

Silver clusters with more than 2 concentric silver shells are scarce. Here, we enable self-assembly and crystallize SD/Ag192a, a highly symmetric silver chalcogenide cluster (SCC) with 192 silver cations in 6 shells and 136 anionic groups in 14 shells. All but 1 of these 20 concentric shells are Platonic or Archimedean solids. All have octahedral or tetrahedral symmetry and align the maximum number of their 2-, 3-, and 4-fold axes of rotational symmetry, thus identifying the cluster as a Keplerate. A rhombic dodecahedron supershell, formed from the first 3 anionic shells, is the keystone for the entire structure. But, nearly all of the edges in these polyhedral shells are too long to represent bonds. What mechanism of coordination chemistry holds the shells together? Like Na⁺ ions held electrostatically inside adjacent cube-shaped anionic compartments in a crystal of NaCl, individual Ag⁺ ions sit inside adjacent octahedron-shaped anionic compartments that fill space. Similarly, like Cl^- ions in NaCl, individual anionic groups sit inside adjacent cationic (Ag⁺) compartments, mostly uniform polyhedra, that also fill space.