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
coordination sphere effects with these single-component precatalysts
for reagent activation and delivery.