Sb@Ni12@Sb20–/+ and Sb@Pd12@Sb20n Cluster Anions, Where n = +1, −1, −3, −4: Multi-Oxidation-State Clusters of Interpenetrating Platonic Solids

K5Sb4 and K3Sb7 Zintl ion precursors react with Pd(PPh3)4 in ethylenediamine/toluene/PBu4+ solutions to give crystals of Sb@Pd12@Sb20n–/PBu4+ salts, where n = 3, 4. The clusters are structurally identical in the two charge states, with nearly perfect Ih point symmetry, and can be viewed as an Sb@Pd12 icosahedron centered inside of an Sb20 dodecahedron. The metric parameters suggest very weak Sb–Sb and Pd–Pd interactions with strong radial Sb–Pd bonds between the Sb20 and Pd12 shells. All-electron DFT analysis shows the 3– ion to be diamagnetic with Ih symmetry and a 1.33 eV HOMO–LUMO gap, whereas the 4– ion undergoes a Jahn–Teller distortion to an S = 1/2 D3d structure with a small 0.1 eV gap. The distortion is predicted to be small and is not discernible by crystallography. Laser desorption–ionization time-of-flight mass spectrometry (LDI-TOF MS) studies of the crystalline samples show intense parent Sb@Pd12@Sb20– ions (negative ion mode) and Sb@Pd12@Sb20+ (positive ion mode) along with series of Sb@Pd12...