Hexacoordinated Carbon

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  1. Henry S. Rzepa--Henry (talk) 15:46, 19 July 2017 (CEST)


--Henry (talk) 18:54, 8 August 2017 (CEST)[edit]

ELF basin centroids (magenta) for di-cation

Normal modes for neutral triplet

Normal modes for 6-coordinate boron cation

Normal modes for 6-coordinate nitrogen tri-cation

ELF analysis
  1. An ELF basin analysis for this dication[1] based on a b3lyp/6-311g(d,p) calculation[2] has been reported [3] as revealing five basal carbon to apical carbon basins of 0.75e and a regular disynaptic apical-C-H basin, thus supporting hexacoordination. QTAIM analysis indicated that value of ρ(r) for the bond critical point located for each of the five apical C-C bonds is 0.156 au. See also Pentacoordinated_Carbon.
  2. An obvious question to ask is what happens to this di-cation if two electrons are added to create a neutral species.[4] In fact the lowest unoccupied orbital has degenerate E-symmetry, and so the spin state of such a neutral species would have to be a triplet to preserve symmetry and avoid Jahn-Teller distortion. This species is a higher-order stationary point, with TWO sets of degenerate normal modes (E2, E1) associated with negative force constants. You can inspect this and other modes by right-clicking in the JSmol window on the left and selecting model from the pop-up window that appears (third menu down from top).
  3. The iso-electronic B1+ and N3+ six-coordinate cations are shown to the left. The first is a stable minimum[5], but the second has four low frequency imaginary modes indicating it is not a minimum.[6] The neutral iso-electronic Be system is also stable.[7]


  1. M. Malischewski, and K. Seppelt, Angewandte Chemie International Edition, 2016, 56, 368-370. DOI:10.1002/anie.201608795 . The crystal structure can be viewed at DOI:10.5517/CCDC.CSD.CC1M71QM .
  2. H. S. Rzepa, 2009, DOI:10.14469/ch/2410
  3. H. S. Rzepa, 2009, DOI:10.14469/hpc/2865
  4. H. S. Rzepa, 2017, DOI:10.14469/hpc/2871
  5. H. S. Rzepa, 2017, DOI:10.14469/hpc/2891
  6. H. S. Rzepa, 2017, DOI:10.14469/hpc/2892
  7. H. S. Rzepa, 2017, DOI:10.14469/hpc/2890