Eclipsed- and Staggered-[Ge₁₈Pd₃{EiPr₃}₆]²– (E = Si, Sn): Positional Isomerism in Deltahedral Zintl Clusters

We report the synthesis and characterization of the cluster anions [Ge 18 Pd 3 {Si i Pr 3 } 6 ] 2– ( 1 ) with a core of face-fused twinned icosahedra, Ge 18 Pd 3, and two sets of three i Pr 3 Si-substituents positioned in “eclipsed” geometry. The new anion is a positional isomer of the recently reported “staggered” stannyl-ligated counterpart [Ge 18 Pd 3 {Sn i Pr 3 } 6 ] 2– ( 2 ), showing the possibility to find such positional isomerism in Zintl clusters. Both anions are characterized by single-crystal X-ray diffraction, 1 H and 13 C 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.