Eclipsed- and Staggered-[Ge₁₈Pd₃{E^<i>i</i>Pr₃}₆]^2– (E = Si, Sn): Positional Isomerism in Deltahedral Zintl Clusters

We report the synthesis and characterization of the cluster anions [Ge18Pd3{SiiPr3}6]2– (1) with a core of face-fused twinned icosahedra, Ge18Pd3, and two sets of three iPr3Si-substituents positioned in “eclipsed” geometry. The new anion is a positional isomer of the recently reported “staggered” stannyl-ligated counterpart [Ge18Pd3{SniPr3}6]2– (2), showing the possibility to find such positional isomerism in Zintl clusters. Both anions are characterized by single-crystal X-ray diffraction, 1H and 13C NMR, and negative-ion ESI-MS. Using relativistic DFT calculations, we elucidate and discuss the reasons for the different positioning of the ligands in the stannyl- and silyl-functionalized species.