| In this paper, palladium nanoparticles and a kind of palladium complex containing SNS ligand have been synthesized and applied in the Heck reaction. Silver nanoparticles and cuprous oxide nanoparticles have been obtained by the same method.(1) Palladium nanoparticles with narrow size distribution were prepared by applying poly(ethyleneglycol) (PEG) and Pd(OAc)2 in the absence of other chemical agents. PEG appeared to act as mild, economic and safe reducing agent compared to other common reducing agent such as N2H2·H2O, NaBH4, and H2. PEG served as stabilizer for the palladium nanoparticles too. The as-prepared catalyst system of palladium nanoparticles/PEG was found to be highly stable and could be reused for 5 times without significant reduce of activity.(2) Ag and Cu2O nanoparticles were successfully fabricated as well by this technique. Ethylene glycol, which was used as reducing agent for the preparation of metal particles at high temperatures (>170℃), was inactive for the reducing of silver at 80℃. Further studies demonstrated that the reducing rate of Ag+ to nano-Ag was remarkably enhanced with the increase of polymer chain length of PEG. The particle size depended upon the reaction temperatures and concentration of the precursor, and an increase in temperature effected a shift of particle size range from ca. 10 nm to 80 nm. In addition, a noticeable change of sphere to polyprism nano-silver was observed when the reaction temperature was elevated to 120℃. The similar phenomena can be observed in the preparation of Cu2O nanoparticles.(3) 4-Hydroxyl-2,6-bis(phenylthiornethyl)pyridine (SNS) palladium(Ⅱ) complex was synthesized and it was applied in Heck reaction. To use K3PO4 as base high to moderate yields could be obtained for phenyl bromides and substituted aryl bromides. To incorporate this Pd-complex into polyglycol (PEG) the catalyst can be recycled conveniently. The rusults shown that SNS-Pd complex is more active than palladium nanoparticles.
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