Deactivation\nModes in Nickel-Mediated Suzuki–Miyaura\nCross-Coupling Reactions Using an NHC-Pyridonate Ligand

The catalytic activity of an NHC-pyridonate-supported\nnickel(0)\ncomplex for Suzuki–Miyaura coupling of aryl halides was evaluated.\nProduct formation was observed in the absence of a basic additive.\nHowever, low turnover numbers resulted from competitive catalyst deactivation.\nThe nature of deactivationdimerization of the nickel(II) aryl\nintermediatewas elucidated through a combination of NMR monitoring,\ndirect synthesis, and X-ray diffraction. Lewis basic and Lewis acidic\nadditives were evaluated with the goal of improving the stability\nof the nickel(II) aryl intermediate but failed to enable catalytic\nturnover. Taken together, these findings highlight both the promise\nand the pitfalls associated with incorporating secondary-sphere Lewis\nbasic groups for cooperative catalysis.