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 development of well‐defined nickel (pre)catalysts with diverse structure and reactivity. In this report, we present ten different bench‐stable, 18‐electron, formally zero‐valent nickel–olefin complexes that are competent pre‐catalysts in various reactions. Our investigation includes preparations of novel, bench‐stable Ni(COD)(L) complexes (COD=1,5‐cyclooctadiene), in which L=quinone, cyclopentadienone, thiophene‐S‐oxide, and fulvene. Characterization by 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. Applications in an assortment of nickel‐catalyzed reactions underscore the complementary nature of the different pre‐catalysts within this toolkit. A series of air‐stable Ni0 pre‐catalysts of the general type Ni (COD) (L) are described, where L=thiophene oxide, quinone, cyclopentadienone, or fulvene. The properties of the complexes are analyzed through computational and experimental techniques. The precatalysts are competent in a variety of nickel‐catalyzed reactions and together constitute a toolkit that overcomes the limitations of both Ni (COD)2 and Ni (COD) (DQ).