Palladium nanoparticles (NPs) stabilized by ImS3-14, a zwitterionic surfactant structurally related to ionic liquids, are revealed here to be good catalysts for the reduction of a large number of substituted aromatic nitro compounds. Our mass spectrometry results are consistent with the formation of amino products in a direct route, where the aromatic nitro compounds are initially reduced to nitroso compounds, which are then reduced to the hydroxylamine derivatives and finally to the anilines. Activation parameters showed that for most Pd catalysts reported in the literature, the mechanism seems to be similar, with lower enthalpy of activation (ΔH‡) being compensated by more negative entropy of activation (ΔS‡). As a result, the reaction is thermally compensated and the rate constants for most reactions rather similar. Furthermore, Pd NPs stabilized by ImS3-14 showed efficient catalytic activities for the reduction of aromatic nitro compounds, with high conversion and good selectivity even using very low loadings of metal.
Keywords:
aromatic nitro reduction; mettalic nanoparticles; catalysis
