Preparation of magnetic chitosan-supported palladium-5-amino-1H-tetrazole complex as a magnetically recyclable catalyst for Suzuki-Miyaura coupling reaction in green media

Abstract

The utilization of various tetrazoles as efficient ligands is a promising method for the functionalization of tetrazole-based heterogeneous catalysts. Their combination with magnetic species and natural supports exposes huge opportunities for the practical applications of heterogeneous catalysts. In this study, a green and novel strategy is applied to synthesize Fe3O4 magnetic nanoparticles (MNPs) incorporated with chitosan (CS) and 5-amino-1H-tetrazole with a long tail ((3-chloropropyl)trimethoxysilane) to immobilize palladium catalyst designated as Fe3O4[email protected](II). The prepared Fe3O4[email protected](II) was used as an efficient and magnetically recyclable catalyst for the Suzuki-Miyaura cross-coupling reaction (SMCR) using a mixture of EtOH/H2O as green media under aerobic conditions. All the expected products were obtained in high yields, indicating the high efficiency of this catalyst for the preparation of various biaryls by SMCR. Various latest techniques were used to characterize Fe3O4[email protected](II), e.g., Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDS) elemental mapping, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning TEM (STEM), high resolution TEM (HR-TEM), vibrating sample magnetometer (VSM), fast Fourier transform (FFT), thermogravimetric analysis (TGA), etc. This study presents a unique example of 5-amino-1H-tetrazole grafted on Fe3O4CS, which can easily be separated using an external magnet and reused five times without significant decrease of catalytic activity. In addition, the introduced method has significant advantages such as the utilization of natural and inexpensive materials, easy work-up, high yields of products, and high catalytic activity.