Stoichiometric and Catalytic Reactions of Thermally Stable Nickel(0) NHC Complexes

Although there are many organic reactions that are catalyzed by either Ni-0 or Pd-0 complexes, in comparison with the case for Pd-0 there has been significantly less work studying coordinatively unsaturated Ni-0 complexes. Here, we develop a simple synthetic route for preparing a number of thermally stable NHC-supported Ni-0 hexadiene complexes in good yield. We examine the stoichiometric reactivity of one of these species and demonstrate that the coordinated hexadiene moiety is labile and can be replaced with a variety of different ligands, including CO, phosphines, isonitriles, and olefins. In addition, we show that the Ni-0 hexadiene complexes are relatively rare examples of homogeneous first-row transition-metal catalysts for the hydrogenation of olefins.