Pd nanoparticles catalyzed ligand-free Heck reaction in ionic liquid microemulsion

Abstract

The H₂O/TX-100/1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) microemulsion is a new green medium, in which the Pd nanoparticles were prepared in situ for the first time. Surfactant TX-100 served as the reductant and the stabilizer of the nanoparticles. The TEM images presented that the monodispersed Pd nanoparticles have a mean particle size of 3 nm. The new medium containing the Pd nanoparticles was used to catalyse the Heck reaction of butyl acrylate with iodobenzene. The effects of various reaction parameters on the Heck reaction are herein discussed. The results indicate that the reaction temperature and the base play key roles in the product yield. The H₂O/TX-100/[BMIM]PF₆ microemulsion containing Pd nanoparticles was found to decrease the reaction time for the Heck reaction compared with conventional solvent system. After the fourth cycle, the catalytic activity of the Pd nanoparticles decreased. Moreover, other Heck reactions relating to the coupling of iodobenzene and methyl acrylate, ethyl acrylate and styrene were also investigated with the high yields determined. All the results indicated that the H₂O/TX-100/[BMIM]PF₆ microemulsion containing the Pd nanoparticles was a very efficient catalyst system for the ligand-free Heck reaction.