Nickel Nanoparticles Stabilized by Trisimidazolium Salts: Synthesis, Characterization and Application as Recyclable Catalysts for the Reduction of Nitroarenes

Abstract Nickel nanoparticles (Ni NPs) from 10 to 17 nm have been prepared by hydrogenation of Ni(COD) 2 (3 bar H 2 , 70 °C) in the presence of trisimidazolium salts (iodide and tetrafluoroborate). The nanoparticles have been structurally and compositionally characterized by transmission electron microscopy (TEM), high‐resolution (HR) TEM, electron diffraction (ED), energy‐dispersive X‐ray spectroscopy (EDS), X‐ray photoelectron spectroscopy (XPS) and elemental analysis. Magnetic measurements reveal that, as expected, the Ni NPs are superparamagnetic at room temperature. These nanomaterials prove efficient as magnetically recoverable catalysts for the transfer hydrogenation of nitroarenes with hydrazine as hydrogen donor. Their superparamagnetic character also ensures no interparticle aggregation once the external magnetic field is removed.