Abstract: Ordered mesoporous Pd(II) organometallic catalyst Pd(II)-PMO(Et) was synthesized by surfactant-directed co-polymerization of ethyl- and Pd(II) organometal-bridged silanes, and was characterized by Fourier transform infrared spectroscopy, NMR, X-ray powder diffraction, transmission electron microscopy, and nitrogen sorption techniques. Compared with the as-prepared Pd(II)-PMO(Et)-G by the grafting method, Pd(II)-PMO(Et) catalyst showed high dispersion of Pd(II) active sites and reduced diffusion limit. Moreover, this catalyst exhibited similar activity to the corresponding Pd(PPh₃)₂Cl₂ homogeneous catalyst in water-medium Suzuki reactions. This can be attributed to the high dispersion of Pd(II) active sites, ordered mesoporous channels, and strong surface hydrophobicity resulted from ethyl fragments embedded in silica walls, the facilitating diffusion and adsorption of organic molecules onto the catalyst in aqueous solution. The Pd(II)-PMO(Et) could be used repeatedly and showed excellent durability, which can be attributed to the effective inhibition of Pd(II) leaching and the high hydrothermal stability of the mesoporous structure.

Key words: ordered mesoporous Pd(II) organometallic catalyst, immobilization of homogeneous catalyst, water medium, arylhalide, Suzuki reaction, co-polymerization