Palladium immobilized on guanidine functionalized magnetic nanoparticles: a highly effective and recoverable catalyst for ultrasound aided Suzuki–Miyaura cross-coupling reactions

Abstract

We designed and prepared a palladium catalyst that can be magnetically recyclable by anchoring guanidine moiety on the surface of Fe₃O₄ nanoparticles, named Fe₃O₄@SiO₂-TCT-Gua-Pd. It was established to be a potent catalyst for the Suzuki–Miyaura cross-coupling reaction (SMCR) in the EtOH/H₂O system under ultrasonic conditions. FT-IR spectroscopy, field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) microanalysis, vibration sample magnetometry (VSM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and inductively coupled plasma atomic emission spectrometry (ICP-AES) analyses were used to characterize the structure of the Fe₃O₄@SiO₂-TCT-Gua-Pd nanoctalyst. The Fe₃O₄@SiO₂-TCT-Gua-Pd catalyst produced favorable coupled products with excellent yields and was harmonious with various aryl halides and aryl boronic acids. The stability, low palladium leaching, and heterogeneous nature of the nanocatalyst were confirmed by a hot-filtration test. The palladium nanocatalyst could be easily recovered by magnetic field separation and recycled at least 6 times in a row without noticeable loss in its catalytic activity.