Excellent Pd-Loaded Magnetic Nanocatalyst on Multicarboxyl and Boronic Acid Biligands

An effective palladium nanocatalyst (Fe₃O₄@SiO₂-FPBA-DTPA-Pd) was proposed and prepared, which was immobilized on magnetic silica with ethylenediamine pentaacetic acid and formylphenylboronic acid as biligands. A series of characterizations showed that Fe₃O₄@SiO₂-FPBA-DTPA-Pd was 5-15 nm and contained 1.44 mmol/g Pd²⁺/Pd⁰. It was stable below 232.7 °C, and its saturation magnetization value was 21.17 emu/g which was easily recycled by a magnet. Its catalytic ability was evaluated through 7 Suzuki reactions and 15 Heck reactions. Results showed that the yields of 14 reactions catalyzed by Fe₃O₄@SiO₂-FPBA-DTPA-Pd were more than 90%, while were better than those of the other two immobilized Pd catalysts on a single diethyltriamine pentaacetic acid (DTPA) group or boronic acid group. Moreover, Fe₃O₄@SiO₂-FPBA-DTPA-Pd showed good reusability in both Suzuki and Heck reactions. In two model Suzuki and Heck reactions, after seven cycles, its yields were still above 95% without significant loss, which exceeded those of many reported catalysts; therefore, it has great potential in future large-scale industrial production.