The Quest for Stable Borozene Core in Main-Group Capped Inverse Sandwich Complexes, [(HE)2B6H6]2- (E=B, Al, Ga, In, and Tl)

The ubiquitous chemistry of benzene led us to explore ways to stabilise analogous borozene, by capping them with appropriate groups. The mismatch in overlap of ring-cap fragment molecular orbitals in [(HB)(2)B6H6](2-) is overcome by replacing the two BH caps with higher congeners of boron. We calculated the relative energies of all the polyhedral structural candidates for [(HE)(2)B6H6](2-) (E=Al-Tl) and found hexagonal bipyramid (HBP) to be more stable with Al-H caps. A global minimum search also gives HBP as the most stable structure for [Al2B6H8](2-). The capped B6H6 ring in [(HAl)(2)B6H6](2-) has aromaticity comparable to that of benzene.