The Synthesis and Catalytic Activity of New Mixed NHC-Phosphite Nickel(0) Complexes

Herein we describe the synthesis and isolation of the first low-valent NHC-phosphite nickel complexes of general formula Ni(NHC)[P(OAr)₃]₂. These three-coordinate Ni(0) compounds were fully characterized, including by X-ray crystallography that highlighted their trigonal planar geometry. The representative complex Ni(IMes)[P(OPh)₃]₂ was used to show that a phosphite ligand is readily substituted in the presence of an aldehyde or nitrile. These stoichiometric studies then led to an investigation of their catalytic properties in the Suzuki-Miyaura cross-coupling reactions between aryl tosylates and aryl boronic acids, a first for such a NHC-Ni catalyst. Finally, mechanistic investigations led to the isolation of a well-defined oxidative addition product.