Water soluble polymer–surfactant complexes-stabilized Pd(0) nanocatalysts: Characterization and structure–activity relationships in biphasic hydrogenation of alkenes and α,β-unsaturated ketones

Abstract

A suitable approach to stabilize palladium nanoparticles in water as a green reaction medium for catalytic hydrogenation reactions is described. Supramolecular self-assemblies, obtained through the mixture of modified polyethyleneimines as amphiphilic polymers and water-soluble ammonium salts as surfactants, were used as efficient protective agents in the synthesis of Pd(0) nanospecies. The size and dispersion of the nanoparticles prepared with these original self-assemblies were characterized by TEM, SAXS and DLS techniques. The performances of the catalysts according to the polymer–surfactant mixtures were investigated in the hydrogenation of alkenes and α,β-unsaturated ketones in pure biphasic water/substrate medium, under mild conditions (room temperature and 1bar H2). The nanocatalysts showed efficient catalytic activities and selectivity towards CC bonds. From investigations, the polymer–surfactant complexes act as cooperative protective agents and a pertinent structure–activity relationship was proposed based on the zeta-potential values and the catalytic activity of the resulting colloids.