σ‐Aromaticity‐Induced Stabilization of Heterometallic Supertetrahedral Clusters [Zn<sub>6</sub>Ge<sub>16</sub>]<sup>4−</sup> and [Cd<sub>6</sub>Ge<sub>16</sub>]<sup>4−</sup>
Hong‐Lei Xu, Ivan A. Popov, Nikolay V. Tkachenko, Zichuan Wang, Alvaro Muñoz‐Castro, Alexander I. Boldyrev, Zhong‐Ming Sun
Abstract
Abstract In this work, the largest heterometallic supertetrahedral clusters, [Zn 6 Ge 16 ] 4− and [Cd 6 Ge 16 ] 4− , were directly self‐assembled through highly‐charged [Ge 4 ] 4− units and transition metal cations, in which 3‐center–2‐electron σ bonding in Ge 2 Zn or Ge 2 Cd triangles plays a vital role in the stabilization of the whole structure. The cluster structures have an open framework with a large central cavity of diameter 4.6 Å for Zn and 5.0 Å for Cd, respectively. Time‐dependent HRESI‐MS spectra show that the larger clusters grow from smaller components with a single [Ge 4 ] 4− and ZnMes 2 units. Calculations performed at the DFT level indicate a very large HOMO–LUMO energy gap in [M 6 Ge 16 ] 4− (2.22 eV), suggesting high kinetic stability that may offer opportunities in materials science. These observations offer a new strategy for the assembly of heterometallic clusters with high symmetry.