ortho-Phenylene bridged palladium bis-N-heterocyclic carbene complexes: synthesis, structure and catalysis

A series of ortho-phenylene bridged palladium bis-NHC complexes has been synthesized. Complexes with imidazolium and benzimidazolium derived NHCs and methyl-/benzyl-wingtips are reported. Bis(benz)imidazoles with a doubly brominated ortho-phenylene bridge could be obtained by an electrophilic substitution reaction. The structure of the complexes could be confirmed by three solid-state structures. All catalysts have been tested in the catalytic functionalisation of propane. The catalytic activity is highly dependent on the ligand, whereas ligand effects on the regioselectivity (n/iso) are much smaller.