Catalytic Properties of Sterically Shielded Carbene Complexes of Palladium in C–C and C–N Coupling Reactions of Haloarenes

New carbene complex catalysts based on palladium chloride, including PEPPSI-complexes (PEPPSI = Pyridine-Enhanced Precatalyst Preparation Stabilization and Initiation), have been synthesized. These catalysts show high efficiency in Buchwald–Hartwig C–N cross-coupling between aryl chlorides/bromides and amines, including sterically shielded reagents, and high efficiency in the Suzuki–Miyaura C–C cross-coupling reaction, where their use results in the formation of several tetra-ortho-substituted biaryls at very low amounts of catalyst under mild conditions. Modification of the catalyst structure to the PEPPSI complex leads to an unexpected decrease in activity in the Buchwald–Hartwig amination, in contrast to the Suzuki–Miyaura reaction, in which the PEPPSI complex showed greater activity in some cases.