Highly active recyclable heterogeneous Pd/ZnO nanoparticle catalyst: sustainable developments for the C-O and C-N bond cross-coupling reactions of aryl halides under ligand-free conditions

Efficient Pd supported on ZnO nanoparticles for the ligand-free O-arylation and N-arylation of phenols and various N-H heterocycles with aryl chlorides, bromides, and iodides were readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% (0.005 g of the catalyst contains 462 x 10(-8) mol% of Pd) which was determined by ICP analysis. This nano sized Pd/ZnO with an average particle size of 20-25 nm and specific surface area 40.61 m(2) g(-1) was used as a new reusable heterogeneous catalyst for the formation of C-O and C-N bonds in organic synthesis. This protocol gives the arylated product in satisfactory yields without any N-2 or Ar flow. The catalyst can be recovered and recycled several times without marked loss of activity.