Unexpected C_(carbene)-X (X: I, Br, Cl) reductive elimination from N-heterocyclic carbene copper halide complexes under oxidative conditions

摘要

The non-spectator roles of NHC ligands have attracted wide attention due to their important implications for reaction mechanisms and subsequent impact on catalyst design. Herein, we report facile C_(carbene)-halogen reductive eliminations from NHC copper halide complexes at RT under oxidative conditions. Density functional calculations on a simplified model system suggest that the reactions occur through oxidation of Cu(I) species to Cu(III) species followed by C_(carbene)-halogen reductive eliminations from NHC Cu(III) halide complexes. Remarkably short C_(carbene)-chloride contacts and rare interactions between the chloride lone pair electrons and the C _(carbene) p_μ orbital were found for the calculated NHC Cu(III) chlorides. The facile C_(carbene)-X reductive elimination reported here warrants consideration as a potential decomposition pathway in reactions involving NHC-supported high-valent metal complexes, especially with late transition metals.