Carbon-Carbon Cross-Coupling Reactions Catalyzed by a Two-Coordinate Nickel(II)-Bis(amido) Complex via Observable NiI, NiII, and NiIII Intermediates

Recently, the development of more sustainable catalytic systems based on abundant first-row metals, especially nickel, for cross-coupling reactions has attracted significant interest. One of the key intermediates invoked in these reactions is a Ni-III-alkyl species, but no such species that is part of a competent catalytic cycle has yet been isolated. Herein, we report a carbon-carbon cross-coupling system based on a two-coordinate Ni-II-bis(amido) complex in which a Ni-III-alkyl species can be isolated and fully characterized. This study details compelling experimental evidence of the role played by this Ni-III-alkyl species as well as those of other key Ni-I and Ni-II intermediates. The catalytic cycle described herein is also one of the first examples of a two-coordinate complex that competently catalyzes an organic transformation, potentially leading to a new class of catalysts based on the unique ability of first-row transition metals to accommodate two-coordinate complexes.