Impregnation of hyper-cross-linked polystyrene (HPS) with tetrahydrofuran (THF) or methanol (ML) solutions containing platinic acid results in the formation of Pt(II) complexes within the nanocavities of HPS. Subsequent reduction of the complexes by H2 yields stable Pt nanoparticles with a mean diameter of 1.3 nm in THF and 1.4 nm in ML. The highest selectivity (98% at 100% conversion) measured during the catalytic oxidation of L-sorbose in water is obtained with the HPS-Pt-THF complex prior to H2 reduction. During an induction period of about 100 min, L-sorbose conversion is negligible while catalytic species develop in situ. The structure of the catalyst isolated after the induction period is analyzed by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Electron micrographs reveal a broad distribution of Pt nanoparticles, 71% of which measure less than or equal to 2.0 nm in diameter. These nanoparticles are most likely responsible for the high catalytic activity and selectivity observed. The formation of nanoparticles measuring up to 5.9 nm in diameter is attributed to the facilitated intercavity transport and aggregation of smaller nanoparticles in swollen HPS. The catalytic properties of these novel Pt nanoparticles are highly robust, remaining stable even after 15 repeated uses.

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Au/Al 2 O 3 and Ni/Al 2 O 3 prepared by deposition-precipitation and impregnation methods, respectively, and Au-Ni/Al 2 O 3 prepared by impregnation of the Au/ Al 2 O 3 system with nickel have been studied by physicochemical methods. The catalysts were tested in allylbenzene isomerization at 443 K. The isomerization on Au/Al 2 O 3 proceeds with a rather low rate, while monometallic Ni/Al 2 O 3 is inactive. Unlike monometallic catalysts, Au-Ni/Al 2 O 3 demonstrates a strong synergetic effect: the isomerization rate on the bimetallic sample exceeds the sum of the rates over the individual metals by an order of magnitude. The catalysts structure was estimated by XPS, DRIFT, and XAS techniques. It was revealed that nickel in Au-Ni/Al 2 O 3 and Ni/Al 2 O 3 exist as Ni 2? cations with the coordination state close to that in the precursor, gold in Au/Al 2 O 3 exist as Au 0 nanoclusters, whereas the Au 0 nanoclusters co-exist with Au 3? cations in the bimetallic Au-Ni/Al 2 O 3 sample. Reasons of the synergetic catalytic effect for Au-Ni/Al 2 O 3 are discussed in terms of the formation of new positively charged Au catalytic centers.

In the present study, we report the synthesis of a series of copper(II) complexes with a wide range of ligands and their testing in the copper catalyzed Chan‐Evans‐Lam (CEL) coupling of aniline and phenylboronic acid. The efficiency of the coupling was directly connected with the ease of the reduction of Cu(II) to Cu(I) of the complexes. The most efficient catalyst was derived from 4‐t‐butyl‐2,5‐bis[(quinolinylimino)methyl]phenolate and two Cu(II) ions. Depending on the counter‐anion nature and the concentration of the reaction mixture, the reaction can be directed to predominant C−N‐bond formation. Forty‐three derivatives of diphenylamine were prepared under the optimized conditions. The proposed mechanism of the catalysis was based on the reduction potential of a series of complexes, molecular weight measurements of the catalytic complex in MeOH and the kinetic studies of aniline and phenylboronic acid coupling. In addition, an 1H NMR experiment in a sealed NMR tube, without external oxygen supply available, proved that no complete Cu(II) to Cu(I) conversion was observed under the condition, ruling out the usually accepted mechanism of the C−N coupling, which included the oxygenation of the intermediately formed Cu(I) complexes after the key step of C−N conversion had already been completed. Instead, a mechanism was proposed, involving an oxygen molecule coordinated to two copper ions in the key C−N bond formation without any detectable conversion of the Cu(II) complexes to Cu(I).