N-heterocyclic carbene Pd(II) complex supported on Fe3O4@SiO2: Highly active, reusable and magnetically separable catalyst for Suzuki-Miyaura cross-coupling reactions in aqueous media

Abstract

A new type magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs heterogeneous catalyst was fabricated and characterized by Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Energy Disperse X-ray analysis (EDX), Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Scanning Electron Microscopy (SEM). The loading amount of Palladium (Pd) to magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs was measured by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. The catalytic activity of magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs heterogeneous catalyst was examined on Suzuki-Miyaura cross-coupling reactions of aryl halides with different substituted arylboronic acid derivatives. All coupling reactions yielded excellent results and high TOF (up to 76528 h−1) in the presence of 2 mg of Fe3O4@SiO2@NHC@Pd-MNPs catalyst (0.0197 mmolg−1, 0.00394 mmol%Pd) at 80 °C in 2-propanol/H2O (1:2). In addition, the magnetic nano Fe3O4@SiO2@NHC@Pd-MNPs catalyst was easily recovered by using an external Nd-magnet and reused for the Suzuki cross-coupling reactions. The catalyst showed strong structural and chemical stability and was reused six times without losing its catalytic activity substantially.