Catalyst Deactivation Modes in Nickel-Catalyzed Suzuki–Miyaura Cross-Coupling Reactions Using an NHC-Pyridonate Ligand

The catalytic activity of an NHC-pyridonate-supported nickel(0) complex for Suzuki–Miyaura coupling of aryl halides was evaluated. Product formation was observed in the absence of a basic additive. However, low turnover numbers resulted from competitive catalyst deactivation. The nature of catalyst deactivation—dimerization of the nickel(II) aryl intermediate—was elucidated through a combination of NMR monitoring, direct synthesis, and X-ray diffraction. This discovery was leveraged to identify additives that enable improved catalyst stability and turnover, thereby highlighting both the promise and pitfalls associated with incorporating secondary-sphere modifications for cooperative catalysis.