Deactivation Modes in Nickel-Mediated Suzuki-Miyaura Cross-Coupling Reactions Using an NHC-Pyridonate Ligand
Abhishek A Kadam1, Medina Afandiyeva1, William W Brennessel1
1Department of Chemistry, University of Rochester, Rochester, New York 14627, United States.
Abstract:
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 deactivation-dimerization of the nickel(II) aryl intermediate-was elucidated through a combination of NMR monitoring, direct synthesis, and X-ray diffraction. Lewis basic and Lewis acidic additives were evaluated with the goal of improving the stability of the nickel(II) aryl intermediate but failed to enable catalytic turnover. Taken together, these findings highlight both the promise and the pitfalls associated with incorporating secondary-sphere Lewis basic groups for cooperative catalysis.
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