Amorphous-carbon-activated palladium metallic clusters

Similar studies in an organic solvent yielded almost the same product [66]. Nanostructured particles of amorphous carbon-activated palladium metallic clusters have been prepared (in situ) at room temperature by ultrasound irradiation of an organometallic precursor, tris-//-[dibenzylideneacetone]dipalladium [(p-CH= CH-CO-CH=CH-5 )3Pd2] in mesitylene. Characterization studies show that the product powder consists of nanosize particles, agglomerated in clusters of approximately 800 A. Each particle is found to have a metallic core, covered by a carbonic shell that plays an important role in the stability of the nanoparticles. The catalytic activity in a Heck reaction, in the absence of phosphine ligands, has been demonstrated. 

Gedanken and coworkers [194] exploited power ultrasound to generate in situ amorphous-carbon-activated palladium metallic clusters that proved to be a catalyst for Mizoroki-Heck reactions (without phosphine ligands) of bromobenzene and styrene (yield to an appreciable extent of 30%). The catalyst is stable in most organic solvents, without showing any palladium powder segregation, even after heating them to 400 °C. 

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