Inhibited Catalyst Activation in (N-Heterocyclic carbene)PdCl2(diethylamine) Complexes by Intramolecular Hydrogen Bonding

The synthesis and characterization of two new (N-heterocyclic carbene)PdCl2(diethylamine) complexes is reported. When compared to the more sigma-donating triethylamine ligand, diethylamine is more tightly bound to Pd due to a rare intramolecular hydrogen bonding interaction with an adjacent chloride. The effect of this stronger coordination in the activation and in the activity of these complexes as precatalysts in the Suzuki-Miyaura cross-coupling reaction is discussed.