NHC/Phosphite Nickel (II) Precatalysts for the C-N Cross-Coupling of Aryl Chlorides under Mild Conditions

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We report the synthesis of three nickel complexes, based on Ni(NHC)[P(OR)3](Ar)Cl, which serve as precatalysts in the C(sp2)−N cross-coupling reaction between chlorobenzene and amines. Reactions involving secondary amines proceeded at room temperature and with low catalytic loading. While anilines and primary alkyl amines coupled at ambient temperatures, mild heating was necessary to achieve optimum yields. The Ni(NHC)[P(OR)3](Ar)Cl complexes are air-stable solids and are discrete precatalysts which operate without the need for an exogenous ligand. Preactivation studies suggest that a 14e- Ni(0) catalytically active species is formed and that both free and Ni-bound phosphite is pre-sent during the reaction.