Optimized Syntheses of Cyclopentadienyl Nickel Chloride Compounds Containing N-Heterocyclic Carbene Ligands for Short Laboratory Periods

Experiments are described for the preparation of imidazolium chloride precursors to N -heterocyclic carbenes and their cyclopentadienyl nickel chloride derivatives. The syntheses have been optimized for second- and third-year undergraduate laboratories that have a maximum programmed length of three hours per week. The experiments are flexible and are readily adapted to a variety of laboratory schedules and student skill levels. The compounds can be characterized by 1 H and 13 C NMR spectroscopy, and the interesting challenges presented by the NMR spectroscopy of the 2,6-diisopropylphenyl substituted imidazole ring are illustrated.