Reactivity-Tunable Palladium Precatalysts with Favorable Catalytic Properties in Suzuki–Miyaura Cross-Coupling Reactions

Abstract In this study, two (HO)R2P→Pd(II)Cl2←NHC precatalysts (1s) were designed and synthesized. Using these precatalysts, yields of unreactive aryl chloride, benzyl chloride, and benzoyl chloride were obtained in three to tens of minutes. Upon deprotonation, density-functional theory calculations and electrospray ionization mass spectrometry revealed that NHC was dissociated from the deprotonated precatalysts. Subsequently, the anionic (O−)R2P→Pd(II)Cl2 species could be reduced using ethoxide to form Pd(0) catalytic species. The cation and anion functions of salt additives were elucidated. The cation size could be used to modulate the catalytic properties of 1s through outer-sphere electrostatic interactions between the coordinated R2P(O−) and alkali metal ions. Through this study, we newly designed Pd(II) precatalysts with superb catalytic properties that are stable and highly efficient.