L-Shaped Heterobidentate Imidazo[1,5-a]pyridin-3-ylidene (N,C)-Ligands for Oxidant-Free AuI/AuIII Catalysis

In the last decade, major advances have been made in homogeneous gold catalysis. However, Au-I/Au-III catalytic cycle remains much less explored due to the reluctance of Au-I to undergo oxidative addition and the stability of the Au-III intermediate. Herein, we report activation of aryl halides at gold(I) enabled by NHC (NHC=N-heterocyclic carbene) ligands through the development of a new class of L-shaped heterobidentate ImPy (ImPy=imidazo[1,5-a]pyridin-3-ylidene) N,C ligands that feature hemilabile character of the amino group in combination with strong sigma-donation of the carbene center in a rigid conformation, imposed by the ligand architecture. Detailed characterization and control studies reveal key ligand features for Au-I/Au-III redox cycle, wherein the hemilabile nitrogen is placed at the coordinating position of a rigid framework. Given the tremendous significance of homogeneous gold catalysis, we anticipate that this ligand platform will find widespread application.

Automated summary

In the past decade, significant progress has been made in homogeneous gold catalysis. However, the exploration of Au-I/Au-III catalytic cycle has been less extensive due to the reluctance of Au-I to undergo oxidative addition and the stability of the Au-III intermediate. In this study, we report the activation of aryl halides at gold(I) by NHC (N-heterocyclic carbene) ligands, achieved through the development of a new class of L-shaped heterobidentate ImPy (imidazo[1,5-a]pyridin-3-ylidene) N,C ligands. This ligand platform shows great potential for widespread application in homogeneous gold catalysis.