In recent years, the non‐covalent interaction of halogen bonding (XB) has found increasing application in organocatalysis. However, reports of the activation of metal‐ligand bonds by XB have so far been limited to a few reactions with elemental iodine or bromine. Herein, we present the activation of metal‐halogen bonds by two classes of inert halogen bond donors and the use of the resulting activated complexes in homogenous gold catalysis. The only recently explored class of iodolium derivatives were shown to be effective activators in two test reactions and their activity could be modulated by blocking of the Lewis acidic sites. Bis(benzimidazolium)‐based halogen bonding activators provided even more rapid conversion, while the non‐iodinated reference compound showed little activity. The role of halogen bonding in the activation of metal‐halogen bonds was further investigated by NMR experiments and DFT calculations, which support the mode of activation occurring via halogen bonding.

Gold catalysis has, over the past decades, provided innovative organic transformations under mild conditions with high chemoselectivities. It receives steadily growing attention thanks to its wide synthetic applicability. The catalytically active form, [L n -Au] + , of ligated gold complexes, [L n -Au-Cl], is formed via halide abstraction. This is typically achieved by anion exchange upon the addition of an appropriate silver salt to the reaction mixture. Herein, an alternative silver-free route for gold activation is presented, making use of halogen bonding to promote halide abstraction. We demonstrate that a catalytic amount of a strong halogen bond donor efficiently activates both gold(I) and gold(III) catalysts. Following the reaction, both the catalyst and the activator are easily recovered. Importantly, this not only reduces the metal waste in a gold-catalyzed process but also enables its upscaling, possibly opening new avenues for its use in industrial settings. Gold is an expensive and limited resource, and its recyclability is of supreme importance. Based on systematic reaction kinetics, NMR spectroscopic, and computational investigations, we describe the mechanism of halogen bond-activated gold(I/III) catalysis using cyclopropanation as a model reaction. Our discovery paves the way for the development of gold-mediated transformations that allow recycling of the precious gold catalyst and that may thereby become useful also for the large-scale generation of complex molecules.

In recent years, the non-covalent interaction of halogen bonding (XB) has found increasing application in organocatalysis. However, reports of the activation of metal-ligand bonds by XB have so far been limited to a few reactions with elemental iodine or bromine. Herein, we present the activation of metal-halogen bonds by two classes of inert halogen bond donors and the use of the resulting activated complexes in homogenous gold catalysis. The only recently explored class of iodolium derivatives were shown to be effective activators in two test reactions and their activity could be modulated by blocking of the Lewis acidic sites. Bis(benzimidazolium)-based halogen bonding activators provided even more rapid conversion, while the non-iodinated reference compound showed little activity. The role of halogen bonding in the activation of metal-halogen bonds was further investigated by NMR experiments and DFT calculations, which support the mode of activation occurring via halogen bonding.

In den letzten Jahren haben Halogenbrücken (XB) als nichtkovalente Wechselwirkung vermehrt Anwendung in der Organokatalyse gefunden. Jedoch beschränkten sich Berichte über die Aktivierung von Metall‐Ligand‐Bindungen durch XB bisher auf Reaktionen mit elementarem Iod oder Brom. Hier präsentieren wir die Aktivierung von Metall‐Halogen‐Bindungen durch zwei Klassen inerter Halogenbrückendonoren und die Anwendung der resultierenden aktivierten Komplexe in der homogenen Goldkatalyse. Iodolium‐Derivate erwiesen sich als effektive Aktivatoren in zwei Testreaktionen und ihre Aktivität konnte über das Blockieren der Lewis‐sauren Positionen moduliert werden. Bis(benzimidazolium)‐basierte Halogenbrückenaktivatoren lieferten noch schnelleren Umsatz, während die nicht‐iodierte Referenzverbindung nur geringe Aktivität zeigte. Die Rolle von Halogenbrücken in der Aktivierung von Metall‐Halogen‐Bindungen wurde darüber hinaus durch NMR‐Experimente und DFT‐Rechnungen untersucht, die Halogenbrücken als Hauptmodus der Aktivierung bestätigten.

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