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submitted on 09.04.2020 and posted on 10.04.2020by Stefan Huber, Julian Wolf, Florian Huber, Nikita Erochok, Flemming Heinen, Vincent Guerin, Claude Legault, Stefan Kirsch
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.