Evaluation of metal catalysts functionalized with well-defined thiolate ligands can be potentially important because such systems can provide a spatial control in the reactivity and selectivity of catalysts. Our group recently discovered a synthetic method utilizing Bunte salts (sodium S-alkylthiosulfates) to generate catalytically active Pd nanoparticles capped with a low density of alkanethiolate ligands. It turned out that the mechanism and selectivity of Pd nanoparticles in different environments was determined by steric hindrance, which was the result of the interaction between substrate and alkanethiolate ligands on Pd nanoparticles. In general, nonpolar or weakly polar solvents such as benzene and chloroform, respectively, promoted the isomerization of allyl alcohol to propanal via the formation of the branched Pd-alkyl intermediate. On the other hand, polar protic solvents such as methanol and water fostered the hydrogenation of allyl alcohol to 1-propanol involving the steric induced formation of linear Pd-alkyl intermediate. The catalysis studies on various Pd nanoparticles with different surface ligand density and average core size showed a strong correlation between the Pd nanoparticle composition and the turnover frequency (TOF) of the isomerization of allyl alcohol. Optimized �Good� Pd nanoparticles with lower surface ligand coverage and larger core size catalyzed the isomerization of various allyl alcohols to carbonyl analogues with high activity and selectivity. Other organic transformations including the tandem semi-hydrogenation and isomerization of propargyl alcohols and the microwave-assisted isomerization of terminal alkenes were also studied using these �Good� Pd nanoparticle catalysts. The synthesis of water soluble Pd nanoparticles using ?-carboxylate-S-alkanethiosulfate salts was also successfully achieved. In general, a decrease in ligand precursor concentration led to an increase in core size and a decrease in ligand surface coverage. Water soluble Pd nanoparticles were examined for the hydrogenation of various unsaturated compounds in both homogeneous and heterogeneous environments.

Synthesis of thiolate-capped Pd nanoparticle catalysts with novel reactivity and selectivity

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.