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

Rhodium Nanoparticles Stabilized by PEG-Tagged Imidazolium Salts as Recyclable Catalysts for the Hydrosilylation of Internal Alkynes and the Reduction of Nitroarenes

PEGylated imidazolium (bromide and tetrafluoroborate) and tris-imidazolium (bromide) salts containing triazole linkers have been used as stabilizers for the preparation of water-soluble rhodium(0) nanoparticles by reduction of rhodium trichloride with sodium borohydride in water at room temperature. The nanomaterials have been characterized (Transmission Electron Microscopy, Electron Diffraction, X-ray Photoelectron Spectroscopy, Inductively Coupled Plasma-Optical Emission Spectroscopy). They proved to be efficient and recyclable catalysts for the stereoselective hydrosilylation of internal alkynes, in the presence or absence of solvent, and in the reduction of nitroarenes to anilines with ammonia-borane as hydrogen donor in aqueous medium (1:4 tetrahydrofuran/water).

Gold nanoparticles stabilized by PEG-tagged imidazolium salts as recyclable catalysts for the synthesis of propargylamines and the cycloisomerization of γ-alkynoic acids

Water-soluble gold nanoparticles prepared in the presence of PEG-tagged tris-imidazolium bromide, containing Au(0) and Au(i) species, are reusable catalysts.

Synthesis of nickel/gallium nanoalloys using a dual-source approach in 1-alkyl-3-methylimidazole ionic liquids

NiGa is a catalyst for the semihydrogenation of alkynes. Here we show the influence of different dispersion times before microwave-induced decomposition of the precursors on the phase purity, as well as the influence of the time of microwave-induced decomposition on the crystallinity of the NiGa nanoparticles. Microwave-induced co-decomposition of all-hydrocarbon precursors [Ni(COD)2] (COD = 1,5-cyclooctadiene) and GaCp* (Cp* = pentamethylcyclopentadienyl) in the ionic liquid [BMIm][NTf2] selectively yields small intermetallic Ni/Ga nanocrystals of 5 ± 1 nm as derived from transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and supported by energy-dispersive X-ray spectrometry (EDX), selected-area energy diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). NiGa@[BMIm][NTf2] catalyze the semihydrogenation of 4-octyne to 4-octene with 100% selectivity towards (E)-4-octene over five runs, but with poor conversion values. IL-free, precipitated NiGa nanoparticles achieve conversion values of over 90% and selectivity of 100% towards alkene over three runs.

Nickel Nanowires: Synthesis, Characterization and Application as Effective Catalysts for the Reduction of Nitroarenes

We have demonstrated a convenient method of synthesizing nickel nanowires (NiNWs), which could be easily tuned to produce materials with a carefully defined nanostructure. By varying the concentration of the Ni precursor, pH of the medium or reaction temperature, we directly affected the diameter of the formed product as well as the yield of the process. The obtained material consisted of straight bundles of NiNWs, which revealed powerful catalytic action for the reduction of nitroarenes to appropriate amine derivatives. A selection of substrates were employed and all of them were successfully converted into the corresponding aromatic amine despite the presence of different substituents on the aromatic ring with high yields, even in large scale reactions. The results showed that NiNW-based catalysts could constitute efficient catalytic systems for the synthesis of aryl amines at industrial levels.