B3Si12: A hexagonal prism with three short B[sbnd]B single bonds at the center coordinated by a Si12 cage and reinforced by aromaticity

Abstract

The structures and properties of B3Si12ˉ/0/+ clusters were investigated by density functional theory calculations combined with mass-selected anion photoelectron spectroscopy. The experimental photoelectron spectrum of cluster anion is reasonably reproduced by theoretical simulations. The global minimum of B3Si12ˉ anion has a B3Si2 trigonal bipyramidal structure with ten capping Si atoms, whereas those of B3Si12 neutral and B3Si12+ cation adopt hexagonal prismatic structures with the B3 unit at the center. In particular, B3Si12ˉ anion is an outstanding closed-shell superatom cluster according to the jellium model (1S21P61D102S21F142P61G18). Furthermore, the NICS values of B3Si12ˉ, B3Si12, and B3Si12+ calculated at points 1 Å above the cage centers are to be −16.8, −56.8, and −51.1 ppm, respectively, suggesting that they are all aromatic.