Synthesis, characterization, and reactivity of [Pd(phosphine)(py)Cl2] (PEPPSI) and [Pd(phosphine)Cl2]2 complexes

The synthesis of novel phosphine palladium PEPPSI and dimer complexes bearing RuPhos, SPhos and XPhos phosphines is reported. The crystal structures of XPhos Pd PEPPSI with pyridine, SPhos Pd PEPPSI with 3-chloropyridine as throw-away ligands and the RuPhos palladium dimer were obtained and compared with previously reported congeners. The catalytic activity of these novel complexes was examined via a C-N coupling reaction involving 4-chloroanisole and morpholine. RuPhos complex 2b proved most active, leading to 97% yield with a low (0.2 mol%) catalyst loading, while phosphine palladium dimers showed significantly lower catalytic activity. However, the addition of 3-pentanone as an activator/stabilizer significantly improved the yields of phosphine dimers and PEPPSI complexes when the reactions were performed in THF.