Development of Palladium Precatalysts that Efficiently Generate LPd(0) Active Species

Palladium catalysts have become central to modern organic synthesis, particularly in the context of cross-coupling reactions to form C-C and C-heteroatom bonds. The development of highly efficient catalyst systems has seen a transition from the use of in situ-generated catalysts derived from a ligand source and palladium precursor to the use of preformed palladium-ligand complexes that can efficiently generate the active species. The design of these systems has focused on optimizing the generation of the LPd(0) species presumed to be the active catalysts with most state-of-the-art ligand systems. This review will highlight the development of Pd(0), Pd(I), and Pd(II) precatalysts that efficiently generate LPd(0) active species with a focus on their activation mechanisms and applications in catalysis.