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 σ-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.