Synthesis and characterization of mesoporous Pd(II) organometal nanoplatelet catalyst for copper-free Sonogashira reaction in water

Abstract

Periodic mesoporous organopalladium(II)-bridged silica with platelet morphology (Pd(II)-PMO-P) was synthesized by the co-condensation of TEOS and Pd[PPh2(CH2)2Si(OC2H5)3]2Cl2 using P123 as structure-directing agent. The as-made Pd(II)-PMO-P samples were characterized with XRD, BET, ICP, SEM, TEM, solid NMR, XPS, as well as FT-IR. It was found that these products were composed of platelets (300–400 nm) with short and straight mesoporous channels (100–200 nm). Organopalladium (II) was integrally incorporated into the walls of silica. Compared to the organopalladium(II)-bridged PMO with irregular pore structure, Pd(II)-PMO-P catalyst exhibited high catalytic efficiency in the water-medium Sonogashira reaction because its short pore channels and nano-sized structures could accelerate the diffusion and adsorption of reactant molecules. Furthermore, the heterogeneous catalyst could be reused several times without significant loss of activity, which efficiently decreases the cost as well as the pollution in order to meet the criteria of green chemistry.