Green reusable Pd nanoparticles embedded in phytochemical resins for mild hydrogenations of nitroarenes

A green chemical preparation of Pd nanoparticles (NPs) embedded in phytochemical resins using a plant extract from Pulicaria odora L. and PdCl2 under ambiant conditions is reported. Two batches of Pd NPs have been prepared: they present homogeneous sizes of respectively 2.2 nm and 3.2 nm depending on the preparation conditions. The Pd NPs were characterized by different techniques (TEM, HRTEM, XRD, XPS and BET) and have been successfully used for the reduction of nitroarenes in EtOH under H-2 at atmospheric pressure at rt in the presence of only 5 mequiv. of Pd. Finally the Pd NPs embedded in resin particles were easily recovered by filtration and used at least seven times without significant loss in efficiency. The residual amount of palladium found in the reaction product is very low (<0.6% of the initial amount). Therefore both preparation of the Pd NPs and their use for hydrogenations of nitroarenes are environmentally benign.