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    Wyświetlanie 1-3 z 3
    Tytuł:
    Ionic [Ru] complex with recyclability by electro-adsorption for efficient catalytic transfer hydrogenation of aryl ketones
    Autorzy:
    Yue, C. J.
    Xue, Q. N.
    Gu, L. P.
    Wang, J. F.
    Powiązania:
    https://bibliotekanauki.pl/articles/778543.pdf
    Data publikacji:
    2017
    Wydawca:
    Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
    Tematy:
    ionic Ru complex
    transfer hydrogenation
    electron-adsorption
    catalyst recovery
    Opis:
    The efficient reuse of homogeneous catalyst is important. Cation complex of [Ru(η6 -p-cymene)(PPh3 )(CH3 CN) Cl]PF6  with different ligands was synthesized and characterized by infrared spectroscopy (IR), 1 H-, 13 C- and 31 P-nuclear magnetic resonance spectroscopy (1 H-, 1 3C- and 31 P-NMR), element analysis (EA), and high resolution mass spectrometry (HR-MS). The complex was used as a catalyst for the hydrogen transfer reduction of carbonyl for the first time, presenting an excellent catalytic performance of 89%–98% conversion of acetophenone and its derivatives. The catalyst may be efficiently reused by the electro-adsorption of 10 times to one catalyst recovery. The cation [Ru] complex presented advantages of both homogeneous and heterogeneous catalysts.
    Źródło:
    Polish Journal of Chemical Technology; 2017, 19, 4; 75-79
    1509-8117
    1899-4741
    Pojawia się w:
    Polish Journal of Chemical Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Asymetryczne przeniesienie wodoru do ketonów katalizowane związkami Rutenu(II) i Rodu(III)
    Asymmetric transfer hydrogenation of ketones catalyzed by Ruthenium(II) and Rhodium(III) complexes
    Autorzy:
    Karczmarska-Wódzka, A.
    Kołodziejska, R.
    Studzińska, R.
    Wróblewski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/172550.pdf
    Data publikacji:
    2012
    Wydawca:
    Polskie Towarzystwo Chemiczne
    Tematy:
    transfer wodoru asymetryczny
    związki kompleksowe Ru(II) i Rh(III)
    chiralne ligandy
    prochiralne związki karbonylowe
    asymmetric transfer hydrogenation
    Ru(II) and Rh(III) complexes
    chiral ligands
    prochiral carbonyl compounds
    Opis:
    Asymmetric hydrogen transfer (ATH) is one of the methods of stereoselective reduction of prochiral carbonyl compounds (Scheme 6). Complexes of the platinum group metals (Noyori catalysts) are the most common catalysts for AT H reactions. The specific structure of the Noyori catalyst allows to activate two hydrogen atoms. These atoms are transferred from donor to acceptor in the form of hydride ion and proton (Scheme 1). Depending on the used catalyst the transfer hydrogenation of ketons can proceed by direct and indirect transfer mechanism. The direct hydride transfer from a donor to an acceptor proceeds via a six-membered transition state (3) (Scheme 2). The indirect hydride transfer proceeds through the formation of an intermediate metal hydride. A monohydride (HLnMH) and or a dihydride (LnMH2) can be formed depending on the catalyst that is used (Scheme 3). In the monohydride route, the reduction proceeds in the inner sphere of the metal (four-membered transition state (4)) or in the outer sphere of the metal (six-membered transition state (5)) (Scheme 4). The proposed reduction of carbonyl compounds in the AT H reaction by Noyori catalysts uses the mechanism of the hydride ion and proton transfer from the donor to the catalyst and the formation of the monohydride. In the indirect transfer hydrogenation the hydride ion and proton are transferred from the monohydride to the acceptor (Scheme 5, 7). AT H reactions that lead to chiral alcohols are conducted in organic solvents or in water. Hydrogen donors most often used in organic solvent reactions are propan-2-ol or an azeotropic mixture of formic acid and triethylamine (Tab. 1, 6). Sodium formate is usually used as hydrogen donor in the reactions conducted in water. Yield and enantioselectivity of the reaction depend on many factors the most important of which are: the structure of a substrate, hydrogen donor and solvent that were used, the reaction time, substrate concentration, and the S/C ratio [2]. In the case of asymmetric reduction conducted in water the solvent pH is also of great importance [3, 7, 8]. An optimal pH range depends on the type of a catalyst [7, 8]. AT H reactions conducted in water are distinguished by a shorter reaction time and higher enantioselectivity than the reactions conducted in organic solvents. In addition, catalysts used in the AT H reactions are more stable in water allowing reuse of the catalyst without loss of its activity. This paper presented examples of the use of specific catalysts in asymmetric reactions of hydrogen transfer. In particular, I drew attention to the reactions running in the aquatic environment due to the above-mentioned advantages of this solvent. The authors focused specifically on bifunctional catalysts based on Ru(II) and Rh(III) on the account of wide usage of the catalysts of that type in AT H reactions in water and their good performance [8, 9, 15, 16, 17, 19, 20, 21, 22]. p-Cymene is the most common aromatic ligand in catalysts based on Ru(II) while in the case of catalysts with Rh(III) the most common is anionic pentamethylcyclopentadienyl ligand. In both cases the second most common ligands are diamines or amino alcohols (Scheme 8). There are better performance and enantioselectivity when diamines are used as ligands. Attempts to replace diamines and amino alcohols by Schiff bases (Scheme 13) in the catalysts containing Rh(III) proved poor results due to a very low enantioselectivity of conducted reactions (Tab. 7).
    Źródło:
    Wiadomości Chemiczne; 2012, 66, 3-4; 273-295
    0043-5104
    2300-0295
    Pojawia się w:
    Wiadomości Chemiczne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A study of ruthenium-based catalysts used in homogeneous transfer hydrogenation of acetophenone
    Autorzy:
    Mikołajczyk, Filip
    Kamiński, Kamil
    Powiązania:
    https://bibliotekanauki.pl/articles/185307.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ruthenium-based catalysts
    transfer hydrogenation
    ketones
    catalysis
    RuCl2(PPh3)3
    katalizatory na bazie rutenu
    przeniesienie uwodornienia
    ketony
    kataliza
    RuCl2 (PPh3) 3
    Opis:
    A detailed comparison of catalytic properties of two different ruthenium-based catalysts in the reaction of homogeneous hydrogenation of acetophenone was performed. Additionally, methods of synthesis of both catalysts were tested and optimized in order to achieve the best possible quality and purity of the final catalysts. NMR analysis was used to analyze and identify the composition of ruthenium compounds and gas chromatography was used to analyze the conversion rate of hydrogenation reactions. It was determined that RuCl2(PPh3)3 obtained with a modified method described by Shaw’s group (Shawet al., 2007) had the best catalytic properties in the reaction performed under conditions described in Liang Wang’s publication (Wang et al., 2014). It was also determined that for concentration ratio of substrate to RuCl2(PPh3)3 amounting to 250:1 the conversion rate was much higher than that of the reaction performed with a double dose of the catalyst. Results of experiments also show that samples of the post-reaction solution should be analyzed right after the reaction, because even if they are stored in low temperature the amount of product can change up to 3–5% compared to the base sample and this change is not predictable. These findings have significant implications for further research of the reaction of homogeneous transfer hydrogenation of ketones. With the right catalysts and methods of their synthesis other parameters of this reaction can be optimized. The most important one is a change of solvent from isopropyl alcohol to a less toxic substance like water. This may increase the value of the reaction in green chemistry and chemical industry.
    Źródło:
    Chemical and Process Engineering; 2019, 40, 2; 213--222
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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