Homoatomic Polyhedra as Structural Modules in Chemistry: What Binds Fullerenes and Homonuclear Zintl Ions?

Ligand-free homoatomic polyhedra are fascinating, not only because of their aesthetic simplicity but also because of their physical and chemical properties. They serve as electron reservoirs, show structural changes that depend upon the electron count, and can be used as "superatomic" building blocks for the targeted assembly of complex structures. Herein, the increasingly pronounced relationship between the fullerides and the nine-atom Zintl ions, the terels, is considered, even though one class of the compounds can be described as large polyhedra with classical bonds and the other as small clusters with nonclassical bonds (Wade rules). In both classes soluble salts with isolated ions, polymer chains, and binary phases with strong interactions between the ions occur.