Pd(0)-Catalyzed Phosphorus−Carbon Bond Formation. Mechanistic and Synthetic Studies on the Role of the Palladium Sources and Anionic Additives

Pd(PPh3)4, Pd(dba)2, Pd(OAc)2, and PdCl2, have been evaluated as possible Pd(0) sources for the palladium-catalyzed P−C bond formation via a cross-coupling of aryl halides with H-phosphonate diesters. It was found that the most efficient catalytic system can be generated from Pd(OAc)2 with a key role being played by Pd(II) and Pd(0) species with coordinated acetate ions. The reactivity of differently ligated Pd(II) complexes was determined, and 31P NMR spectroscopy studies were carried out to provide mechanistic interpretations for the observed differences between the catalytic systems.