Be₄ B₁₂ ⁺ : A Covalently Bonded Archimedean Beryllo-Borospherene

A new class of beryllium-boron clusters, beryllo-borospherene, is described herein theoretically. When beryllium is gradually added to the B₁₂ motif, it undergoes drastic structural modifications. The global minimum of the Be₄ B₁₂ ⁺ cluster is an Archimedean beryllo-borospherene in a ² A₁ electronic ground state, composed of four boron triangles linked at each corner, resulting in a truncated tetrahedron with four B₆ rings capped with four beryllium atoms. Beryllium forms strong bonding with the boron clusters through strong electrostatic and covalent interactions. For instance, the bonding between a beryllium atom and Be₃ B₁₂ unit is best described as a Be⁺ fragment in a ² P excited state forming a strong and polarized electron-sharing bond with Be₃ B₁₂ , followed by several dative interactions by employing its vacant s, p, and very high-lying d orbitals. Counterintuitively, for an s-block element, the p orbitals of beryllium are the most crucial atomic orbitals for bonding rather than s orbitals.