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 2 L, 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.

Five new, bifunctional imidazolium-thioether ligands of the general formula RS(CH 2 ) n (imidazolium) + ArBr -(n = 2 or 3, R = Et or tBu, Ar = 2,4,6-trimethylphenyl or 2,6-diisopropylphenyl) have been synthesised in good overall yields by a general method and used as N-heterocyclic carbene precursors for complexation studies on various transition metals (Ni II , Pd II and Rh I ). Sulfur does not coordinate the nickel cen-