Catalytic activity of green synthesized iron-palladium bimetallic nanoparticles on Sonogashira and Stille cross-coupling reactions

Abstract

Catalytic applications of plant extract mediated green synthesized bimetallic NPs have attracted significant interest as an eco-friendly method. The Sonogashira and Stille carbon-carbon cross coupling reactions are widely used in the synthesis of complex organic molecules. The objective of this research was to investigate the catalytic activity of Fe-Pd bimetallic nanoparticles, synthesized using banana leaf extract of Musa Paradisiaca, on Sonogashira and Stille cross coupling reactions. Banana leaf extract (BLE) was prepared by boiling fresh banana leaves (50 g) in deionized water (150 mL) for 30 minutes. The UV-Vis spectrum of the BLE showed peaks at 200-270 nm range and 350 nm, which correspond to the polyphenolic compounds that can act as reducing, capping and stabilizing agents during nanoparticle synthesis. PdCl2 (0.050 M) and Fe2O3 (0.0028 M) were used as precursors to synthesize the bimetallic nanoparticles. Synthesized Fe Pd nanoparticles were characterized by X-ray diffraction. Reflections at 39.82⁰, 46.31⁰ and 67.65⁰ are well indexed to the (111), (200), and (220) planes of crystalline palladium. The powder X-ray diffraction study confirmed the crystal structure of zero-valent Pd. The synthesized Fe-Pd nanoparticles showed magnetic properties which is an important feature for catalytic reusability. The catalytic activity of synthesized Fe-Pd NPs was studied in Sonogashira and Stille C-C cross coupling reactions. The optimum reaction conditions for Sonogashira C-C cross-coupling reaction of bromobenzene and phenylacetylene were found out to be 0.63% Fe-Pd nanoparticles (with respect to bromobenzene) in water (solvent) using K2CO3 (2 mmol) as a base at 60 °C for 30 min. The purified product, diphenyl acetylene was isolated in 47% yield. Stille cross-coupling reaction was carried out using Fe-Pd NPs (2% w/w, relative to bromobenzene) as the catalyst and K2CO3 (2.0 mmol) as the base at 80 °C in water for 1 h. The Stille cross-coupling reaction of bromobenzene with tributylphenylstannane yielded pure biphenyl in 87%. It can be concluded that Fe-Pd bimetallic NPs synthesized using banana leaf extract can be applied as a catalyst on Sonogashira and Stille cross-coupling reactions.