Nickel(II) complexes with bifunctional phosphine–imidazolium ligands and their catalytic activity in the Kumada–Corriu coupling reaction

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Zwitterionic Ni(II) complexes of type NiX 3(NCN +), (NCN + = 1-(2-diphenylphosphinoethyl)-3-(2,4,6-trimethylphenyl)imidazolium and X = Cl, 6; Br, 7), have been prepared by addition of NCN + bromide ( 1a) or tetrafluoroborate ( 1b) to NiX 2L, and characterised by X-ray crystallography. They have been used as catalytic precursors in the Kumada–Corriu coupling reaction between phenylmagnesium chloride and 4-chloroanisole, yielding high catalytic activities. Stoechiometric deprotonation investigations did not provide clear evidence for the formation of coordinated carbene species.