hide
Free keywords:
density functional calculations; EPR spectroscopy; N-hetero-cyclic carbenes; radicals; X-ray diffraction
Abstract:
One‐electron reduction of C2‐arylated 1,3‐imidazoli(ni)um salts (IPrAr)Br (Ar=Ph, 3 a; 4‐DMP, 3 b; 4‐DMP=4‐Me2NC6H4) and (SIPrAr)I (Ar=Ph, 4 a; 4‐Tol, 4 b) derived from classical NHCs (IPr=:C{N(2,6‐iPr2C6H3)}2CHCH, 1; SIPr=:C{N(2,6‐iPr2C6H3)}2CH2CH2, 2) gave radicals [(IPrAr)]. (Ar=Ph, 5 a; 4‐DMP, 5 b) and [(SIPrAr)]. (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.
