Chiral, Sterically Demanding N-Heterocyclic Carbenes Fused into a Heterobiaryl Skeleton: Design, Synthesis, and Structural Analysis

A series of Cu(I), Ag(I), and Au(I) complexes incorporating a new family of imidazopyridin-3-ylidene ligands substituted by a diphenylpyrrolidino group at N(1) and aryl groups at C(5) has been synthesized and their structures determined by X-ray diffraction analysis. This structural study has revealed an extremely high steric protection of the metal center by the bulky heterobicyclic carbenes, while the inversion at the exocyclic N(sp3) atom provides a remarkable flexibility.