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

Zwitterionic Ni(II) complexes of type NiX3(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 NiX2L, 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.