Highly Active Fe3O4@SBA-15@NHC-Pd Catalyst for Suzuki–Miyaura Cross-Coupling Reaction

Abstract

A novel Pd-NHC functionalized magnetic Fe3O4@SBA-15@NHC-Pd was synthesized and used as an efficient heterogeneous catalyst in the Suzuki–Miyaura C–C bond formation reactions. The Fe3O4@SBA-15@NHC-Pd characterized by X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray analysis (EDX), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA). The Inductively Coupled Plasma-Optical emission spectroscopy (ICP-OES) analysis was used to determine the exact amount of Pd (0.33 wt%) in Fe3O4@SBA-15@NHC-Pd. The TEM images of the catalyst showed the existence of palladium nanoparticles immobilized in the catalyst's structure, while no reducing agent was used. The NHC moieties in the catalyst structure could be stabilize Pd(0) nanoparticles prevents agglomeration. The magnetic catalyst was effectively used in the Suzuki–Miyaura cross-coupling reaction of substituted phenylboronic acid derivatives with (hetero)aryl bromides in the presence of a K2CO3 at room temperature in aqueous media and magnetic catalyst could be simply extracted from the reaction mixture by an external magnet. Different aryl bromides were converted to coupled-products in excellent yields with spectacular TOFs values (up to 1,960,339 h−1); in the presence of 1 mg of Fe3O4@SBA-15@NHC-Pd catalyst (contains 3.1 × 10–6 mol% Pd) at room temperature in aqueous media. After reusability experiments, it is found that this catalyst was effectively used up to ten times in the reaction with almost consistent catalytic efficiency. A decrease in the activity of the 10th reused catalyst was found as 9%.