2-Pyridyl-benzimidazole-Pd(II)/Pd(0) Supported on Magnetic Mesoporous Silica: Aerobic Oxidation of Benzyl Alcohols/Benzaldehydes and Reduction of Nitroarenes.

2-(2-Pyridyl)benzimidazole (PyBzIm) was supported onto magnetic mesoporous silica, Fe3O4@SiO2@SBA-15 via the click chemistry. The supported ligand was treated with Na2PdCl4 in methanol to afford Fe3O4@SiO2@SBA-PyBzIm-Pd(II) as a magnetically retrievable supported catalyst. The catalyst was fully characterized by conventional methods. X-ray photoelectron spectroscopy (XPS) studies confirmed some C = N nitrogen atoms interact with palladium in the + 2 oxidation state. The prepared catalyst was found to catalyze the aerobic oxidation of benzyl alcohols and benzaldehydes to the corresponding benzoic acids, and excellent conversions were obtained. The magnetic catalyst showed a very low metal leaching (3.9%) in the first run. Fe3O4@SiO2@SBA-PyBzIm-Pd(II) was then treated with aqueous NaBH4 to give Fe3O4@SBA-PyBzIm-Pd(0). The obtained catalyst was found to catalyze the transfer hydrogenation of nitroarenes to the corresponding anilines in the presence of hydrazine, and excellent yields were obtained. The prepared catalysts present an excellent recycling efficiency over seven consecutive runs without significant loss of catalyst reactivity. [ABSTRACT FROM AUTHOR]