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Crystalline Radicals Derived from Classical N‐Heterocyclic Carbenes
Author(s) -
Rottschäfer Dennis,
Neumann Beate,
Stammler HansGeorg,
van Gastel Maurice,
Andrada Diego M.,
Ghadwal Rajendra S.
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201801596
Subject(s) - radical , chemistry , stereochemistry , organic chemistry
Abstract One‐electron reduction of C2‐arylated 1,3‐imidazoli(ni)um salts (IPr Ar )Br (Ar=Ph, 3 a ; 4‐DMP, 3 b ; 4‐DMP=4‐Me 2 NC 6 H 4 ) and (SIPr Ar )I (Ar=Ph, 4 a ; 4‐Tol, 4 b ) derived from classical NHCs (IPr=:C{N(2,6‐ i Pr 2 C 6 H 3 )} 2 CHCH, 1 ; SIPr=:C{N(2,6‐ i Pr 2 C 6 H 3 )} 2 CH 2 CH 2 , 2 ) gave radicals [(IPr Ar )] . (Ar=Ph, 5 a ; 4‐DMP, 5 b ) and [(SIPr Ar )] . (Ar=Ph, 6 a ; 4‐Tol, 6 b ). Each of 5 a , b and 6 a , b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid‐state characterization of NHC‐derived carbon‐centered radicals 6 a , b by single‐crystal X‐ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group.