Be 4 B 12 + : 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 B 12 motif, it undergoes drastic structural modifications. The global minimum of the Be 4 B 12 + cluster is an Archimedean beryllo-borospherene in a 2 A 1 electronic ground state, composed of four boron triangles linked at each corner, resulting in a truncated tetrahedron with four B 6 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 Be 3 B 12 unit is best described as a Be + fragment in a 2 P excited state forming a strong and polarized electron-sharing bond with Be 3 B 12 , 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.