Simple Synthesis of CpNi(NHC)Cl Complexes (Cp = Cyclopentadienyl; NHC = N-Heterocyclic Carbene)

The reaction of saturated and unsaturated imidazolium salts with nickelocene in refluxing THF results in the formation of NHC complexes of general formula CpNi(NHC)Cl (NHC = SIMes ( 2 ), IPr ( 3 ), SIPr ( 4 )). This protonation of Cp 2 Ni was also tested using phosphonium salts, and the reaction of nickelocene with triethylphosphonium chloride leads to CpNi(PEt 3 )Cl ( 5 ). All compounds were characterized by NMR and X-ray crystallography. The catalytic activity of the NHC compounds was tested in aryl amination (Buchwald−Hartwig reaction) and in aryl halide dehalogenation reactions.