The Pentagonal-Pyramidal Hexamethylbenzene Dication: Many Shades of Coordination Chemistry at Carbon

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Abstract

A recent report on the crystal structure of the pentagonal-pyramidal hexamethylbenzene dication C-6(CH3)(6)(2+) by Malischewski and Seppelt [Angew. Chem. Int. Ed. 2017, 56, 368] confirmed the structural proposal made in the first report of this compound in 1973 by Hogeveen and Kwant [Tetrahedron Lett. 1973, 14, 1665]. The widespread attention that this compound quickly gained led us to reinvestigate its electronic structure. On the basis of intrinsic bond orbital analysis, effective oxidation state analysis, ring current analysis, and comparison with well-established coordination complexes, it is demonstrated that the central carbon atom behaves like a transition metal. The central (apical) carbon atom, although best described as a highly Lewis-acidic carbon atom coordinated with an anionic cyclopentadienyl ligand, is also capable of acting as an electron-pair donor to a formal CH3+ group. The different roles of coordination chemistry are discussed.

Original languageEnglish
Pages (from-to)12340-12345
Number of pages6
JournalChemistry
Volume24
Issue number47
DOIs
Publication statusPublished - 22-Aug-2018

Keywords

  • bond theory
  • carbon
  • coordination modes
  • density functional calculations
  • donor-acceptor systems
  • MAIN-GROUP COMPOUNDS
  • CHEMICAL CONCEPTS
  • OXIDATION-STATE
  • QUANTUM-THEORY
  • COMPLEXES
  • CATION
  • BONDS
  • MOLECULES
  • LIGANDS
  • DENSITY

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