A theoretical approach to the role of different types of electrons in planar elongated boron clusters

We analyze the thermodynamic stability of some small elongated boron clusters and confirm the relationship between their planarity and their inherent electron configuration [...σ 2( n +1) π 1 2( n +1) π 2 2 n ]. Delocalized σ electrons in an elongated bare boron cluster and 2c-2e C-H bonds in a corresponding elongated hydrocarbon play a vital role in maintaining their planar structure. Through the eigenstates derived from a model of a particle moving in a rectangle, the rectangle model, our study suggests that the larger planar elongated boron clusters are not thermodynamically stable. A partition of the electron densities which is consistent with the electron count, points out that the dianionic, neutral and dicationic B 10 2−/0/2+ clusters are doubly σ and π aromatic, singly π aromatic, and doubly σ and π antiaromatic, respectively. While the stability of planar elongated pure boron clusters is determined by their [...σ 2( n +1) π 1 2( n +1) π 2 2 n ] electronic configuration, the rectangle model can rationalize the π electronic configuration of rectangle-shaped structures.