Multi-Layered, Covalently Supported Ionic Liquid Phase (mlc-SILP) as Highly Cross-Linked Support for Recyclable Palladium Catalysts for the Suzuki Reaction in Aqueous Medium

The reaction between an excess of 1,4‐bis(3‐vinylimidazolium‐1‐yl) bromide and a mercaptopropyl‐modified amorphous silica gel or ordered mesoporous silica SBA‐15 in the presence of azobisisobutyronitrile (AIBN) afforded new materials, which have a high loading of imidazolium moieties. These materials, which contain a highly cross‐linked polymeric network, have been denoted as multi‐layered, covalently supported ionic liquid phase (mlc‐SILP) and have been used as support for palladium catalysts containing a high loading of the metal (10 wt%). Such materials were characterized by several techniques (13C magic angle spinning nuclear magnetic resonance, the Brunauer–Emmett–Teller technique, small‐angle X‐ray scattering, X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission electron microscopy). The presence of a homogeneous distribution of palladium nanoparticles was established. The palladium catalysts displayed good activity allowing the synthesis of several biphenyl compounds in high yields working with only 0.1 mol% of palladium loading at mild temperatures (room temperature or 50 °C) in ethanol/water. Reactions carried out on a 10‐mmol scale required only 10 mg of catalysts. Good recyclability was observed.