Carbene Transfer Reactivities of Nickel(II)–N-Heterocyclic Carbene Complexes and Their Applications in the Synthesis of Metal–NHC Complexes

We describe a new synthetic procedure for transition-metal N-heterocyclic carbene complexes (NHCs). A number of Pd­(II), Pt­(II), Co­(III), and Ru­(II) complexes containing functionalized NHCs have been obtained in good to excellent yields using NiII–NHC complexes as carbene transfer reagents. NiII–NHC complexes are easily prepared from the direct reactions of the corresponding imidazolium salts with commercially available Raney nickel powder. The byproduct of transmetalation reactions, NiCl2, can be easily removed by simple filtration. This study offers a new, economical, and practical synthetic method for metal–NHC complexes.