Facile-prepared sulfonated water-soluble PEPPSI-Pd-NHC catalysts for aerobic aqueous Suzuki–Miyaura cross-coupling reactions†
Four sulfonated water-soluble PEPPSI-Pd-NHC complexes (2a–2d) are prepared in a straightforward two-step synthesis. Their activities have been examined in Suzuki–Miyaura cross-coupling reactions in water under air. Complex 2d, bearing a 2,6-diisopropylphenyl substituent, shows the best catalytic activity and a variety of aryl bromides with a catalyst loading of 0.1 mol% can be efficiently activated even at room temperature. The catalyst is recyclable and can be employed in at least four consecutive runs without significant loss in performance. Furthermore, TEM analysis, kinetic studies and mercury poisoning experiments indicate that Pd nanoparticles are formed during the reactions.