Synthesis and characterization of FePd magnetic nanoparticles modified with chiral BINAP ligand as a recoverable catalyst vehicle for the asymmetric coupling reaction

Abstract

The initial thermal decomposition of iron carbonyl (Fe(CO)₅), followed by reduction of palladium acetylacetonate (Pd(acac)₂) produced FePd nanoparticles (NPs) with an Fe_xO_y-rich core and a Pd-rich shell. The as-synthesized NPs were subsequently treated with (S)-2,2′-bis(diphenylphosphino)-1,1′-binaphthene ((S)-BINAP) as a chiral modifier, which provides them with the optical activity to show a negative Cotton effect in the circular dichroism (CD) spectrum. Characterization by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), superconducting quantum interface device (SQUID) and X-ray absorption fine structure (XAFS) measurements was performed. The FePd NPs modified with (S)-BINAP had a mean diameter of ca. 5.6 nm, and exhibited superparamagnetic behavior at 300 K with zero remanence and coercivity. The FePd-(S)-BINAP was shown to catalyze the asymmetric Suzuki–Miyaura coupling reaction with easy recovery from the reaction mixture by applying an external magnet. The designed architecture enabled the powerful combination of two functionalities, magnetism that responds to a magnetic field for easy recycling, as well as an optically active catalytic center that promotes the asymmetric coupling reaction.