Application of Tripodal Linker Units to Immobilized Diphenylphosphine Palladium Complex Catalysts for Suzuki-Miyaura Coupling Reactions of Aryl Bromide: Effect of Immobilization Method of Phosphine Ligand on Catalytic Performance

Abstract

A tripodal linker unit that tightly binds to a silica surface via three independent Si–O–Si bonds was applied to immobilize diphenylphosphino-palladium complex catalysts onto ordered mesoporous silica. The diphenylphosphino-functionalized silica materials were prepared by: (i) grafting the bromine-substituted tripodal linker unit onto mesoporous silica and a subsequent treatment with potassium diphenylphosphide (the “bottom-up” method), (ii) directly grafting pre-synthesized tripodal diphenylphosphino ligands onto silica (the “top-down” method). The catalytic properties were evaluated in the Suzuki-Miyaura coupling reaction of aryl bromides. The tripodally immobilized catalyst prepared via the “bottom-up” method showed lower leaching levels of palladium and phosphorus compared to catalyst prepared via the “top-down” method.