[Co<sub>3</sub>@Ge<sub>6</sub>Sn<sub>18</sub>]<sup>5–</sup>: A Giant σ-Aromatic Cluster Analogous to H<sub>3</sub><sup>+</sup> and Li<sub>3</sub><sup>+</sup>
Ya‐Shan Huang, Hong‐Lei Xu, Wen‐Juan Tian, Zisheng Li, Sílvia Escayola, Miquel Solà, Alvaro Muñoz‐Castro, Zhong‐Ming Sun
Abstract
Aromaticity is one of the most important concepts in chemistry and has been successfully extended to all-metal clusters. However, the study of all-metallic aromatic clusters remains in its early stages, with σ-aromatic clusters mostly limited to small sizes (≤12) that often require external stabilization. In this work, we report the first Ge/Sn-based trimer, [Co 3 @Ge 6 Sn 18 ] 5–, which can be rationalized as the fusion of three [Co – @Ge 3 Sn 6 4– ] units via a Ge 3 face. Theoretical studies have revealed that two σ-electrons are delocalized across the entire trimer, with the spherical aromaticity of each [Co@Ge 3 Sn 6 ] unit and the global σ-aromaticity of [Co 3 @Ge 6 Sn 18 ] 5– further supported by its electron delocalization and magnetic behavior. As a result, this trimer can be viewed as a giant σ-aromatic counterpart to triatomic H 3 + and Li 3 + . Our findings suggest the potential for synthesizing cluster-of-cluster analogs of discrete all-metallic aromatic species, such as Al 4 2–, and further enhance our understanding of chemical bonding.