New Pincer CC′C Complexes of Nickel(II) via Chloronickelation of Alkyne-Bearing N-Heterocyclic Carbenes

Pincer-like nickel complexes of N-heterocyclic carbenes, [Ni(3-chloro-1,4-di(N-aryl-N′-imidazolylidene)but-2-en-2-yl)(CH3CN)](PF6), have been prepared from the transmetalation reactions of the corresponding [Ag2(1,4-di(N-aryl-N′-imidazol-2-ylidene)but-2-yne)2](PF6)2 and [Ni(PPh3)2Cl2]. X-ray diffraction studies show that the distorted square-planar nickel(II) complexes are supported by anionic terdentate ligands with two imidazolylidenes and one vinyl carbon donor originated from chloronickelation of the triple bond. Further studies suggest that the nickel complexes are excellent catalysts for Kumada−Corriu coupling reactions of aryl chlorides even at room temperature.