 Here the sp2 hybridization, and consequently the planarity of the atoms of and those directly bonded to the sp2 centers, forces the tops of the p-orbitals of the basal carbons towards each other, thus creating a solid base for the apical carbon to sit on.Stiffening the configuration by a bridge between the homo-atoms, converting the base of the pyramid, to a norbornadiene, creates an even more stable structure.According to the results presented in Table 1, a five-sided pyramidal carbocation will be divalent.