Palladium complexes of o-xylylene-linked alkoxybenzimidazolin-2-ylidenes containing aryl N-substituents: examples of C-H activation and the formation of a tri-nuclear palladium complex

摘要

Palladium complexes of new bidentate N-heterocyclic carbene (NHC) incorporating benzimidazolin-2-ylidene units have been synthesized and structurally and spectroscopically characterised. The NHC ligands are furnished with aryl substituents on the nitrogen atoms and electron-donating butoxy groups on the benzo-fused ring. The incorporation of these aryl substituents on the bis(NHC) ligands leads to interesting and unexpected conformations around the palladium atoms, and interesting reactivity, including cyclometallation and the formation of a tri-nuclear species. One of the complexes has been studied in an initial series of Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions but shows moderate to poor activity.