Synthesis, Structure, and Hydroboration Reactivity of Anionic Nickel(0) Complexes Supported by Bidentate NHC-Pyridone Ligands

A family of anionic, formally nickel(0) complexes supported by bidentate NHC–pyridone ligands is described. The unsymmetric chelating environment and capping [K(18-crown-6)]+ countercation allow isolation of single-component, monometallic complexes in high yield. The steric and electronic properties are assessed through a battery of experimental (NMR, IR, UV/vis, X-ray diffraction) and computational tools. Catalytic activity for highly branched-selective hydroboration of styrene with HBpin is demonstrated. Control experiments implicate an important role of the pyridone in establishing reactivity and regioselectivity, suggesting the potential to leverage secondary coordina-tion sphere effects with these single-component precatalysts for reagent activation and delivery.