Intraligand Charge Transfer Enables Visible‐Light‐Mediated Nickel‐Catalyzed Cross‐Coupling Reactions**
Cristian Cavedon, Sebastian Gisbertz, Susanne Reischauer, Sarah Vogl, Eric Sperlich, John H. Burke, Rachel F. Wallick, Stefanie Schrottke, Wei‐Hsin Hsu, Lucia Anghileri, Yannik Pfeifer, Noah Richter, Christian Teutloff, Henrike M. Müller‐Werkmeister, Dario Cambié, Peter H. Seeberger, Josh Vura‐Weis, Renske M. van der Veen, Arne Thomas, Bartholomäus Pieber
Abstract
Abstract We demonstrate that several visible‐light‐mediated carbon−heteroatom cross‐coupling reactions can be carried out using a photoactive Ni II precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl 2 ). The activation of this precatalyst towards cross‐coupling reactions follows a hitherto undisclosed mechanism that is different from previously reported light‐responsive nickel complexes that undergo metal‐to‐ligand charge transfer. Theoretical and spectroscopic investigations revealed that irradiation of Ni(Czbpy)Cl 2 with visible light causes an initial intraligand charge transfer event that triggers productive catalysis. Ligand polymerization affords a porous, recyclable organic polymer for heterogeneous nickel catalysis of cross‐coupling reactions. The heterogeneous catalyst shows stable performance in a packed‐bed flow reactor during a week of continuous operation.