Preparation of a novel heterogeneous palladium nanocatalyst based on carboxyl modified magnetic nanoparticles and its applications in Suzuki-Miyaura coupling reactions

Abstract

In this paper, an active, recyclable and stable magnetic palladium nanocatalyst (Fe3O4@SiO2-DTPA-Pd) was reported which could catalyze Suzuki coupling reaction. The Pd was stably hold by the three nitrogen atoms at the inside and four acetic acid groups at the outside of the chelating ligand ethylenediaminepentaacetic acid (DTPA) on the surface of core-shell magnetic Fe3O4@SiO2 microspheres. The prepared Fe3O4@SiO2-DTPA-Pd was systematically characterized. Results showed its size was 10–20 nm with 0.535 mmol/g Pd2+/Pd0. It could monodisperse in liquid, was thermally stable and good magnetic response from the high saturation magnetization value at 35.9 emu/g. Its activity was evaluated through Suzuki coupling reactions between 14 types of aryl halides and phenylboronic acid under optimized reaction conditions. It exhibited excellent activities and good applicability to substituted iodobenzene and bromobenzene. The yield of 4-bromobenzonitrile was up to 97.93%. Furthermore, the Fe3O4@SiO2-DTPA-Pd catalyst was stable, reusable and conveniently recovered by applying an external magnetic field. After 20 consecutive reaction cycles, the yield was still above 85%, which showed a superior heterogeneous advantage over other catalysts reported in the literature and had the huge potential in actual application of industry.