Bis(Oxime Palladacycle) Supported on Magnetized SBA-15 as an Efficient and Retriveble Catalyst for the Mizoroki–Heck Reaction

Abstract

Herein, we report the anchoring of a bis(oxime palladacycle) adduct on magnetic mesoporous silica (Fe₃O₄@SBA-15). Magnetic mesoporous silica was successively treated with (3-aminopropyl) triethoxysilane (APTES), cyanuric chloride (CC), and 4-hydroxyacetophenone oxime-derived palladacycle to give Fe₃O₄@SBA-AP-CC-bis(oxime palladacycle). The obtained nano-catalyst was characterized by FT-IR spectroscopy, CP MAS ¹³C NMR spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), Brunauer–Emmett–Teller surface area measurement (S_BET) and X-ray diffraction spectroscopy (XRD). X‐Ray photoelectron spectroscopy (XPS) corroborated the (+ 2) oxidation number for palladium. The catalytic potential of Fe₃O₄@SBA-AP-CC-bis(oxime palladacycle) was explored in the Mizoroki–Heck reaction. The effects of different reaction conditions, including the solvent, the base, temperature, and palladium content, were studied in detail. The N-methylpyrrolidone (NMP) solvent, 0.5 mol% of the Pd-catalyst, the NaOAc base, and the reaction temperature of 120 °C, provided the best conditions for the Heck cross-coupling reaction. The catalyst showed a wide substrate scope, including aryl halides (I, Br, Cl) and olefins, in the Mizoroki–Heck reaction, using low catalyst loadings viz., Pd 0.09 mol%. The bis(oxime palladacycle) enjoys easy magnetic separation, stability, and recyclability over five runs.