Air-stable, recyclable, and regenerative phosphine sulfide palladium(0) catalysts for C-C coupling reaction

Mononuclear phosphine sulfide Pd(0) complexes and a polymer-supported triphenylphosphine sulfide Pd(0) complex were prepared as new air-stable Pd(0) catalysts for C-C coupling reactions. The phosphine sulfide Pd(0) complexes are not decomposed after completion of Suzuki-Miyaura coupling, and the polymer-supported Pd(0) catalyst is practically recyclable, while phosphine Pd(0) complexes are decomposed into inactive Pd(0) black after consuming the substrates. New catalytic activity of Pd(0) that promotes chalcogen atom replacement of phosphine chalcogenides (R₃P=X, X = O, S, Se) is reported. A mechanistic study revealed that the new catalytic chalcogen replacement results from activation of the P=X bond as well as promotion of the oxidative chalcogenide formation. The intermediate phosphine was successfully trapped as a phosphine Pd(II) complex, and the P=X bond activation is applicable to regeneration of phosphine or phosphine sulfide from oxidized phosphine.