Pd immobilized on amidoxime-functionalized Mesoporous SBA-15: A novel and highly active heterogeneous catalyst for Suzuki-Miyaura coupling reactions

Herein we described the synthesis of a novel SBA-15/AO/Pd(II) nanocatalyst by grafting of amidoxime on SBA-15 and subsequent deposition of palladium chlorides. Prior to grafting of amidoxime (AO), the prepared [2-cyanoethyl]-functionalized Mesoporous SBA-15 through combining of 2-cyanoethyltriethoxysilane and SBA-15 was treated with hydroxylamine. The amidoxime grafted SBA-15 (SBA-15/AO) were then used as platform for in situ deposition of Pd complex. The materials were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), inductivity coupled plasma (ICP), nitrogen adsorption-desorption, and Fourier transform infrared (FTIR) spectroscopy. SBA-15/AO/Pd(II) are novel phosphine-free recyclable heterogeneous catalyst for Suzuki coupling reaction of aryl halides (I, Br, Cl) with phenylboronic acid to provide the corresponding products. These cross-coupled products were produced in excellent yields under mild conditions at extremely low palladium loading (similar to 0.2 mol%) with perfect high turnover frequencies (TOFs). The heterogeneous catalyst can be readily recovered by simple filtration and reused six times with loss in its activity. (C) 2014 Elsevier B.V. All rights reserved.