Structure, stability and bonding of the leapfrog B₂₄ ^{0 ,±1,±2}

Two new structural motifs of the B₂₄ clusters are constructed by use of the leapfrog transformation. The resulting leapfrog B₂₄ has either a bowl shape with a square vacancy or a quasi-planar 2D close-packed triangular boron sheet. The neutral and ionic forms of the latter are found to be more stable than their homologous leapfrog bowl clusters, with the exception of the dicationic B₂₄ ⁺² . While the leapfrog isomer is less stable than the tubular double ring in the neutral state, it becomes competitive in some ionic states. The nucleus independent chemical shift, electron localization function, ring current maps and the electronic structure of leapfrog B₂₄ clusters reveal them to behave as aromatics.