Tetrahedral [Tt4]4– Zintl Anions Through Solution Chemistry: Syntheses and Crystal Structures of the Ammoniates Rb4Sn4·2NH3, Cs4Sn4·2NH3, and Rb4Pb4·2NH3

The crystalline isotypic solvates Rb₄Sn₄·2NH₃, Cs₄Sn₄·2NH₃, and Rb₄Pb₄·2NH₃ have been synthesized using the direct reduction of elemental tin or tetraphenyltin, respectively, with heavier alkali metals or the dissolution of the binary phase RbPb in liquid ammonia. These compounds contain the cluster ions Sn₄]^4– or Pb₄]^4– respectively. This is the first time thatTt₄]^4– ions (Tt = tetrels) are detected as result of a solution reaction. The accommodation of the ammonia molecules, which build up ion‐dipole interactions to alkali metal cations, requires some modifications of the crystal structures compared to the binary phases RbSn, CsSn, and RbPb. The tetrahedral Tt₄]^4– anions have a slightly lower coordination by Rb⁺ or Cs⁺ cations and, furthermore, the intercluster distances show a remarkable increase.