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.

A Mukaiyama aldol reaction can be catalyzed by bidentate halogen bond donors with very high efficiency. The halogenated catalysts were stable over multiple consecutive runs, which supports the halogen-bond-based mode of catalysis.

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.

A series of cationic monodentate and bidentate iodo(benz)­imidazolium-based halogen bond (XB) donors were employed as catalysts in a Mukaiyama aldol reaction. While 5 mol% of a monodentate variant showed noticeable activity, a <i>syn</i>-preorganized bidentate XB donor provided a strong performance even with 0.5 mol% loading. In contrast to the very active BAr^F₄ salts, PF₆ or OTf salts were either inactive or showed background reaction. Repetition experiments clearly ruled out a potential hidden catalysis by elemental iodine and demonstrated the stability of our catalyst over three consecutive cycles.