The Largest Metalloid Group14 Cluster, Ge18[Si(SiMe3)3]6: An Intermediate on the Way to Elemental Germanium

The oxidation of [Ge-9(Hyp)(3)](-) (Hyp=Si(SiMe3)(3)) with an Fe-II salt leads to Ge-18(Hyp)(6) (1), the largest Group14 metalloid cluster that has been structurally characterized to date. The arrangement of the 18 germanium atoms in 1 shows similarities to that found in the solid-state structure Ge(cF136). Furthermore, 1 can be described as a macropolyhedral cluster of two Ge-9 units. Quantum-chemical calculations further hint at a strained arrangement so that 1 can be considered as a first trapped intermediate on the way from Ge-9 units to elemental germanium with the clathrate-II structure (Ge(cF136)).