Structurally Diverse Bench-Stable Nickel(0) Pre-Catalysts: A Practical Toolkit for In Situ Ligation Protocols

A flurry of recent research has centered on harnessing the power of nickel catalysis in organic synthesis. These efforts have been bolstered by contemporaneous synthesis, characterization, and optimization of well-defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present the development of ten different bench-stable, 18-electron, formally zero-valent nickel–olefin complexes that are shown to be competent pre-catalysts in various reactions. Our investigation includes preparations of novel, bench stable Ni(COD)(L) complexes, in which L = quinone, cyclopentadienone, thiophene-S-oxide, and fulvene. Characterization by a battery of techniques, including NMR, IR, single-crystal X-ray diffraction, cyclic voltammetry, thermogravimetric analysis, and natural bond orbital analysis sheds light on the structure, bonding, and properties of these complexes. Kinetic profiling across a series of representative reactions reveals reactivity differences that stem from the nature of the ancillary ligand, underscoring the complementary relationships between each pre-catalyst within this toolkit.