Palladium nanoparticles generated from allylpalladium chloride in situ: A simple and highly efficient catalytic system for Mizoroki–Heck reactions

The Mizoroki–Heck reactions of aryl halides catalyzed by palladium nanoparticles generated in situ from a simple allyl palladium precursor were investigated in argon. The high turnover numbers of 9,300,000 have been obtained with 4-bromobenzonitrile as substrate and 3500 with 4-nitrochlorobenzene. When the reaction was performed in air, a low yield was given, but it could be improved obviously by addition of PEG-400. The main reason was that inactive Pd(II) species could be rapidly reduced to the active Pd(0) by PEG. In other word, the existence of air and PEG led to a synergistic effect which the oxidation by air prevents the aggregation of Pd NPs and the reduction by PEG maintains the high activity of Pd(0) species.

Graphical abstractThe Mizoroki–Heck reactions of aryl halides catalyzed by palladium nanoparticles generated in situ from a simple allyl palladium precursor were investigated. Turnover numbers of 9,300,000 have been gained with 4-bromobenzonitrile as substrate and 3500 with 4-nitrochlorobenzene. A lower yield was gained in air, but it could be improved obviously by addition of PEG-400.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► TEM results explain the reactivity distinction of the different catalyst precursors for the Mizoroki–Heck reaction. ► The catalytic system of [Pd(C3H5)Cl]2 as catalyst precursor shows high activity toward aryl halides. ► The effect of air and PEG on the Mizoroki–Heck reaction is revealed.