Viable aromatic Be_nH_n stars enclosing a planar hypercoordinate boron or late transition metal

Monocyclic B_n rings can act as n-electron σ-donors to stabilize a non-classical planar hypercoordinate atom at ring center, forming wheel-like structures. Herein, we report that Be_nH_n rings can also serve as n-electron σ-donors to construct star-like structures including B©Be₆H₆⁺ and TM©Be₇H₇^q (TM is a group 10-12 metal with q = -1, 0, and 1, respectively) by complying with octet or 18-electron rules. Electronic structure analyses show that these species are stabilized by the σ-donation and π-backdonation between the central atom and the peripheral Be_nH_n ring, the favorable Coulomb attraction due to the negative-positive-negative charge population pattern on the central atom, the middle Be_n layer, and the outer H_n layer, as well as the σ-π double aromaticity. Importantly, three of the ten species, including B©Be₆H₆⁺, Cu©Be₇H₇, and Au