Preparation and Characterisation of Pd Nanoclusters in Hyperbranched Aramid Templates to be used in Homogeneous Catalysis

In the present paper the potential use of hyperbranched (HB) aramids as metallic solution stabilisers and carriers for homogeneous catalysis is outlined. Aramids, synthesised either from A2 + B3 reagents [namely, p‐phenylenediamine (PPD) and trimesic acid (TMA)] or from an AB2 monomer [i.e., 5‐(4‐aminobenzamido)isophtalic acid, named ABZAIA], have been used to stabilise palladium nanoclusters dispersed in two solvent media, namely N,N′‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The influence of the nature of the polymeric support as well as of the solvent medium on both cluster dimensions and stability of the solutions has been investigated. Indeed, the interactions between the polymeric support and the metallic precursor (PdCl2), as revealed by 1H NMR spectroscopy, involve only the amino groups of the HB aramids. Metal nanocluster dimensions and stability are strongly dependent on the polymer used as a stabilizer. Transmission electron microscopy (TEM) analysis has shown that the presence of HB polymer in the solution reduces cluster dimensions and allows the obtaining of stable systems. The low concentration of NH2 end groups in the poly(AB2) system leads to the formation of Pd particles of rather low dimensions with a high tendency to aggregate. All prepared solutions are stable under inert atmosphere for at least a month, with an improved stabilisation when using the poly(A2 + B3) system for more than five months. A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution. magnified image A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution.