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Halogenated Benzene Cation Radicals
Author(s) -
Molski Matthias J.,
Mollenhauer Doreen,
Gohr Sebastian,
Paulus Beate,
Khanfar Monther A.,
Shorafa Hashem,
Strauss Steven H.,
Seppelt Konrad
Publication year - 2012
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.201102960
Subject(s) - radical , chemistry , electron paramagnetic resonance , crystallography , benzene , crystal structure , paramagnetism , single crystal , nuclear magnetic resonance , organic chemistry , quantum mechanics , physics
Abstract The halogenated benzenes C 6 HF 5 , 2,4,6‐C 6 H 3 F 3 , 2,3,5,6‐C 6 H 2 F 4 , C 6 F 6 , C 6 Cl 6 , C 6 Br 6 , and C 6 I 6 were converted into their corresponding cation radicals by using various strong oxidants. The cation‐radical salts were isolated and characterized by electron paramagnetic resonance (EPR) spectroscopy and by single‐crystal X‐ray diffraction. The thermal stability of the cation radicals increased with decreasing hydrogen content. As expected, the cation radicals [C 6 HF 5 ] + and 2,3,5,6‐[C 6 H 2 F 4 ] + had structures with the same geometry as C 6 HF 5 and 2,3,5,6‐[C 6 H 2 F 4 ]. In contrast, the cation radicals [C 6 F 6 ] + , [C 6 Cl 6 ] + , and possibly also [C 6 Br 6 ] + exhibited Jahn–Teller‐distorted geometries in the crystalline state. In the case of C 6 F 6 + Sb 2 F 11 − , two low‐symmetry geometries were observed in the same crystal. Interestingly, the structures of the cation radicals 2,4,6‐[C 6 H 3 F 3 ] + and C 6 I 6 + did not exhibit Jahn–Teller distortions. DFT calculations showed that the explanation for the lack of distortion of these cations from the D 3 h or D 6 h symmetry of the neutral benzene precursor was different for 2,4,6‐[C 6 H 3 F 3 ] + than for [C 6 I 6 ] + .