Synthesis, Characterization and Catalytic Applications of Palladium Nanoparticle-Cored Dendrimers Stabilized by Metal-Carbon Bonds

The synthesis and characterization of four generations of palladium nanoparticle-cored Frechet-type dendrimers (Pd-Gn) possessing direct palladiumcarbon bonds are reported. These coreshell materials have been synthesized by the simultaneous reduction of different generation diazodendrons and PdII in an organic medium. The resulting organicinorganic hybrid materials were characterized by IR, NMR and UV/Vis spectroscopic techniques. The formation of nearly spherical particles of 24 nm diameter was confirmed by TEM studies. The efficiency of one member of this series, Pd-G1, in catalysing important CC bond-forming reactions such as Suzuki, Stille and Hiyama coupling reactions was investigated. The results clearly show that Pd-G1 can efficiently catalyse the cross-coupling of arylboronic acids, aryl stannanes and organosilicon compounds with differently substituted aryl halides in addition to efficiently catalysing hydrogenation reactions. The catalyst exhibited good recovery and recyclability in Suzuki coupling reactions. The study suggests that a single catalyst capable of catalysing several reactions can be designed.