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The Pentagonal‐Pyramidal Hexamethylbenzene Dication: Many Shades of Coordination Chemistry at Carbon
Author(s) -
Klein Johannes E. M. N.,
Havenith Remco W. A.,
Knizia Gerald
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201705812
Subject(s) - hexamethylbenzene , dication , chemistry , crystallography , ligand (biochemistry) , ring (chemistry) , atom (system on chip) , electronic structure , oxidation state , coordination complex , crystal structure , transition metal , electron counting , carbon fibers , electron configuration , metal , computational chemistry , electron , molecule , ion , benzene , materials science , catalysis , organic chemistry , receptor , computer science , embedded system , biochemistry , composite number , composite material , quantum mechanics , physics
A recent report on the crystal structure of the pentagonal‐pyramidal hexamethylbenzene dication C 6 (CH 3 ) 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 CH 3 + group. The different roles of coordination chemistry are discussed.