Cation-Controlled Olefin Isomerization Catalysis with Palladium Pincer Complexes

A series of palladium(II) pincer complexes with different substituents on the amine donor has been prepared and studied in olefin isomerization catalysis. Installing a macrocycle into the pincer ligand enables cation-switchable positional olefin isomerization: no reaction is observed with the catalyst alone, while in the presence of Li+ salts isomerization proceeds cleanly. Mechanistic studies implicate a key role of highly electrophilic Pd centers with accessible olefin binding sites in catalysis.