Ni(i)–Ni(iii) cycle in Buchwald–Hartwig amination of aryl bromide mediated by NHC-ligated Ni(i) complexes

Abstract

Intermediate amide complexes of NHC-ligated monovalent nickel in Buchwald–Hartwig amination of aryl halides were isolated and structurally characterized. The amide complexes reacted with aryl bromide to form a cross-coupling product. Low-temperature observation of the oxidative addition product of the Ni(I) amide complex with aryl bromide indicated the presence of a Ni(III) intermediate. The results showed that a well-defined mononuclear NHC–Ni(I) complex can act as a key intermediate in homogeneous catalysis.