Comparison of dppf-Supported Nickel Precatalysts for the Suzuki-Miyaura Reaction: The Observation and Activity of Nickel(I).

Ni-based precatalysts for the Suzuki-Miyaura reaction have potential chemical and economic advantages compared to commonly used Pd systems. Here, we compare Ni precatalysts for the Suzuki-Miyaura reaction supported by the dppf ligand in 3 oxidation states, 0, I and II. Surprisingly, at 80 °C they give similar catalytic activity, with all systems generating significant amounts of Ni(I) during the reaction. At room temperature a readily accessible bench-stable Ni(II) precatalyst is highly active and can couple synthetically important heterocyclic substrates. Our work conclusively establishes that Ni(I) species are relevant in reactions typically proposed to involve exclusively Ni(0) and Ni(II) complexes.