Phosphinite-functionalized silica and hexagonal mesoporous silica containing palladium nanoparticles in Heck coupling reaction: synthesis, characterization, and catalytic activity

A series of mono, di and tri phosphinite ligands functionalized on modified silica and modified hexagonal mesoporous silica (HMS) were synthesized and characterized. The complexation of these ligands with PdCl2 was carried out to obtain palladium supported on phosphinite functionalized silica. TEM images of the catalysts showed that Pd dispersed in nanoparticle size on these heterogeneous catalytic systems. Hexagonal and mesoporous structures with high surface area of HMS were examined by SEM, TEM and BET techniques. In a typical Heck coupling reaction (HCR), catalytic activity of the Pd catalysts was compared. It was shown that di-functionalized phosphinite ligands react better for both silica and HMS. Aryl halides (also known as haloarenes or halogenoarenes) of different varieties with olefinic substrates in the HCR exhibited high efficiency and stability for the selected catalyst. Repeating Heck reaction cycles illustrated that the catalyst could be recycled.