Sb@Ni@Sb and Sb@Pd@Sb Cluster Anions, Where n = +1, -1, -3, -4: Multi-Oxidation-State Clusters of Interpenetrating Platonic Solids.

KSb and KSb Zintl ion precursors react with Pd(PPh) in ethylenediamine/toluene/PBu solutions to give crystals of Sb@Pd@Sb/PBu salts, where n = 3, 4. The clusters are structurally identical in the two charge states, with nearly perfect I point symmetry, and can be viewed as an Sb@Pd icosahedron centered inside of an Sb dodecahedron. The metric parameters suggest very weak Sb-Sb and Pd-Pd interactions with strong radial Sb-Pd bonds between the Sb and Pd shells. All-electron DFT analysis shows the 3- ion to be diamagnetic with I symmetry and a 1.33 eV HOMO-LUMO gap, whereas the 4- ion undergoes a Jahn-Teller distortion to an S = 1/2 D 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@Pd@Sb ions (negative ion mode) and Sb@Pd@Sb (positive ion mode) along with series of Sb@Pd@Sb ions. Ni(cyclooctadiene) reacts with KSb in en/tol/BuPBr solvent mixtures to give black precipitates of Sb@Ni@Sb salts that give similar Sb@Ni@Sb parent ions and Sb@Ni@Sb degradation series in the respective LDI-TOF MS studies. The solid-state and gas-phase studies of the icosahedral Sb@M@Sb ions show that the clusters can exist in the -4, -3, -1, +1 (M = Pd) and +1, -1 (M = Ni) oxidation states. These multiple-charge-state clusters are reminiscent of redox-active fullerenes (e.g., C, where n = +1, 0, -1, -2, -3, -4, -5, -6).