One-Pot, Single-Step, and Gram-Scale Synthesis of Mononuclear [(η6-arene)Ni(N-heterocyclic carbene)] Complexes: Useful Precursors of the Ni0-NHC Unit

Recently, the combination of Ni(0) and N-heterocyclic carbenes (NHCs) has been paid special attention because of its high reactivity toward bond-forming reactions and the activation of unreactive bonds. Thus, it would be very worthwhile to provide a highly reactive, easily accessible, and versatile (NiNHC)-N-0 precursor. Herein we report a one-pot, single-step, and gram-scale method for the synthesis of [(eta(6)-arene)Ni(NHC)] complexes from commercially available Ni(cod)(2) and NHC (or its salt) via hydrogenation of COD. The structure and bonding situations of [(eta(6)-arene)Ni(NHC)]s were evaluated by NMR, X-ray, and DFT studies. An application to the synthesis of Ni-0-NHC complexes via ligand exchange reactions is also demonstrated.