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. Lowerature 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.
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