(IPr)Pd(pydc) (pydc = pyridine-2,6-dicarboxylate) – A highly active precatalyst for the sterically hindered C–N coupling reactions

A new class of well-defined NHC–Pd complexes incorporating a pyridine-2-carboxylate or pyridine-2,6-dicarboxylate ligand has been synthesized. These novel complexes exhibited prominent catalytic activity in the sterically hindered C–N coupling reactions at elevated temperature, but relatively inferior reactivity at low temperature. The distinctly different reactivity of these NHC–Pd complexes was presumed to be associated with their unique structures of ancillary ligands.