Intraligand Charge Transfer Enables Visible-Light-Mediated Nickel-Catalyzed Cross-Coupling Reactions

• Cristian Cavedon^a,b, Sebastian Gisbertz^a,b,Susanne Reischauer^a,b, Sarah Vogl^c, Eric Sperlich^d, John H. Burke^e, Rachel F. Wallick^e, Stefanie Schrottke^f, Wei-Hsin Hsu^a, Lucia Anghileri^a,b, Yannik Pfeifer^d, Noah Richter^a, Christian Teutloff^f, Henrike Müller-Werkmeister^d, Dario Cambié^a, Peter H. Seeberger^a,b, Josh Vura-Weis^e, Renske M. van der Veen^e,g, Arne Thomas^c, Bartholomäus Pieber^a

• ^aDepartment of Biomolecular Systems, Max-Planck-Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany
• ^bDepartment of Chemistry and Biochemistry, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
• ^cDepartment of Chemistry, Functional Materials, Technische Universität Berlin, Hardenbergstraße 40, 10623 Berlin, Germany
• ^dInstitute of Chemistry, University of Potsdam, Karl-Liebknecht-Strasse 24–25, 14476 Potsdam, Germany
• ^eDepartment of Chemistry, University of Illinois Urbana-Champaign, Urbana, Illinois, 61801 USA
• ^fDepartment of Physics, Freie Universität Berlin, Arnimallee 22, 14195 Berlin, Germany
• ^gHelmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

We demonstrate that several visible-light-mediated carbon−heteroatom cross-coupling reactions can be carried out using a photoactive NiII precatalyst that forms in situ from a nickel salt and a bipyridine ligand decorated with two carbazole groups (Ni(Czbpy)Cl2). 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)Cl2 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.

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