Boron di- and tri-cations

Previous work on boron di- and tri-cations is reviewed. The structural chemistry of representative examples of these classes of compound has been probed by determination of the single-crystal X-ray structures of [(4-Mepy)(4)B]Br-3 and [py(3)BH]Br-2. The electronic structures of the polycations [(py)(3)BH](2+), [(py)(3)BBr](2+), [(4-Mepy)(3)BH](2+), [(4-Mepy)(4)B](3+), [(Me3P)(3)BH](2+) and [(Me3P)(4)B](3+) have been examined by DFT methods. The atomic charges on these cations were evaluated by Mulliken, natural population analysis (NPA), Hirschfeld and Voronoi deformation density (VDD) methods.