Photoactive Nickel Complexes in Cross‐Coupling Catalysis

Transition metal catalyzed cross‐coupling reactions are important in chemical synthesis for the formation of C−C and C‐heteroatom bonds. Suitable catalysts are frequently based on palladium or nickel, and lately the cheaper and more abundant first‐row transition metal element has been much in focus. The combination of nickel catalysis with photoredox chemistry has opened new synthetic possibilities, and in some cases electronically excited states of nickel complexes play a key role. This is a remarkable finding, because photo‐excited metal complexes are underexplored in the context of organic bond‐forming reactions, and because the photophysics and the photochemistry of first‐row transition metal complexes are underdeveloped in comparison with their precious metal‐based congeners. Consequently, there is much potential for innovation at the interface of synthetic‐organic and physical‐inorganic chemistry. This Minireview highlights recent key findings in light‐driven nickel catalysis and identifies essential concepts for the exploitation of photoactive nickel complexes in organic synthesis. Photo‐excited about Ni: Photophysically and photochemically relevant aspects of light‐driven cross‐coupling reactions by nickel catalysis are reviewed. The importance of energetically low‐lying triplet excited states is highlighted, along with recent key findings in light‐driven nickel catalysis. Essential concepts for the use of photoactive nickel complexes in organic synthesis are identified.