Ab initio topological analysis of the electronic density in isobutonium cations

Studies performed on isobutonium cations at the ab initio level show that f ive different stable structures can be characterized. The two structures mo st energetically favored correspond to van der Waals complexes, one of them between CH4 and i-C3H7+ and one of smaller energy between H-2 and the C4H9 + cation. Among the isobutonium cations, the most stable structure correspo nds to the C-isobutonium cation where a three-center two-electron bond is f ormed. The isobutonium cations on the H are significantly higher in energy. The topology of the electronic density charge of the isobutonium cations i s studied, at ab initio level, using the theory of atoms in molecules (AIM) developed by Bader. The electronic delocalization that operates through th e sigma bonds in saturated molecules and specifically in protonated alkanes can be studied by means of the analysis of the charge density and of the L aplacian of the electronic charge density at the bond critical points.