Preparation and Characterization of Palladium Nanoparticles Supported on Phosphinated Poly(Vinyl Alcohol) As New Recyclable Catalyst and Their Application for Heck Cross-coupling Reactions

Diphenylphosphinated poly(vinyl alcohols) (DPP-PVA) were synthesized by the insertion of chlorodiphenylphosphine to PVA in the presence of triethyl amine as base. The structure of this new polymer was confirmed by FT-IR and NMR spectroscopy. This polymer can be used as ligand for the preparation of nanoparticles of palladium. The complexation of PVA-grafted phosphinite with palladium(II) acetate was carried out to obtain the heterogeneous catalytic system. X-ray diffraction techniques, X-ray photoelectron spectroscopy, and transmission electron microscopy imaging revealed that palladium was dispersed into the nanometer scale through the support. This catalytic system showed excellent activity in the cross-coupling Heck reactions of olefinic compounds with aryl iodides, bromides as well as chlorides and gave high yields within short reaction times. Elemental analysis of Pd by the inductively coupled plasma technique on the supported catalyst exhibited low leaching of the metal into the solution. The catalyst can be reused several times in the repeated Heck reaction cycles without considerable loss in its activity.