Click Polymer-Supported Palladium Nanoparticles as Highly Efficient Catalysts for Olefin Hydrogenation and Suzuki Coupling Reactions under Ambient Conditions

Complexation of palladium(II) acetate [Pd(OAC)(2)] or dipotassium tetrachloropalladate [K2PdCl4] to click polymers functionalized with phenyl, ferrocenyl and sodium sulfonate groups gave polymeric palladium(II)-triazolyl complexes that were reduced to click polymer-stabilized palladium nanoparticles (PdNPs). Transmission electron microscopy (TEM) showed that reduction using sodium borohydride (NaBH,) produced PdNPs in the 1-3 run range of diameters depending on the nature of the functional group, whereas slow reduction using methanol yielded PdNPs in the 22-25 nm range. The most active of these PdNPs (0.01% mot Pd), stabilized by poly(ferrocenyltriazolylmethyl)styrene, catalyzed the hydrogenation of styrene at 25 degrees C and 1 atm hydrogen, with turnover numbers (TONs) of 200,000. When stabilized by the water-soluble poly(sodium sulfonate-triazolylmethyl)styrene, the PdNPs (0.01% mot Pd) catalyze the Suzuki-Miyaura coupling between iodobenzene (PhI) and phenylboronic acid [PhB(OH)(2)] in water/ethanol (H2O/EtOH) at 25 degrees C with TONs of 8,200. This high catalytic activity is comparable to that obtained with click dendrimer-stabilized PdNPs under ambient conditions.