1193-81-3Relevant articles and documents
Synthesis and Applications of (Pyridyl)imine Fe(II) Complexes as Catalysts in Transfer Hydrogenation of Ketones
Kumah, Robert T.,Vijayan, Paranthaman,Ojwach, Stephen O.
, p. 344 - 352 (2021)
Abstract: Chiral (pyridyl)imine Fe(II) complexes, [Fe(L1)3]2+[PF6?]2, (Fe1), [Fe(L2)3]2+[PF6?]2, (Fe2), [Fe(L3)3]2+[PF6?]2 (Fe3), and [Fe(L4)3]2+[PF6?]2 (Fe4) were synthesised by reactions of synthons (S-)-1-phenyl-N-(pyridine-2-yl) ethylidine)ethanamine (L1), (R-)-1-phenyl-N-(pyridine-2-yl) ethylidine) ethanamine (L2), (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3) and (S)-1-phenyl-N-(pyridine-2-yl methylene)ethanamine (L4) with the FeCl2 salt. The solid-state structure of complex Fe4 showed that the?Fe atom contains three units of bidentate bound ligand L4 to form a six-coordinate cationic compound. The Fe(II) complexes were evaluated as catalysts in asymmetric transfer hydrogenation of ketones reactions and showed moderate catalytic activities with low enantioselectivity. Catalytic activities of the respective complexes were regulated by the nature of the metal complexes, ketone substrate and reaction conditions. Mercury and sub-stoichiometric poisoning experiments implicate possible formation of both active Fe(0) nanoparticles and Fe(II) homogeneous intermediates. Graphic Abstract: [Figure not available: see fulltext.]
Nanoheterogeneous catalytic hydrogenation of arenes: Evaluation of the surfactant-stabilized aqueous ruthenium(O) colloidal suspension
Nowicki, Audrey,Boulaire, Virginie Le,Roucoux, Alain
, p. 2326 - 2330 (2007)
The hydrogenation of various aromatic compounds by a surfactant-stabilized aqueous ruthenium(O) colloidal suspension was investigated. The nanocatalysts in the size range of 2.5-3.5 nm were synthesized by reducing ruthenium trichloride salt with sodium borohydride and were stabilized by the highly water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride salt according to our classical approach. The efficient catalytic reactions were performed at room temperature and under hydrogen pressure. The effect of the stirring, namely magnetic stir bar or gas projection impeller, was also studied. A comparison with an analogous rhodium nanocatalyst is described.
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Johnson
, p. 864 (1959)
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Tuning the structure and catalytic activity of Ru nanoparticle catalysts by single 3d transition-metal atoms in Ru12-metalloporphyrin precursors
Muratsugu, Satoshi,Yamaguchi, Atsuki,Yokota, Gen-Ichi,Maeno, Tomoaki,Tada, Mizuki
, p. 4842 - 4845 (2018)
Ru nanoparticle catalysts were prepared from Ru12-metalloporphyrin complex precursors containing 3d transition-metal atoms attached to SiO2 surfaces. The single 3d metal atoms at the central position of the Ru12-metalloporphyrin complex precursors exerted a significant influence on the structures and hydrogenation performance of the Ru nanoparticles on the SiO2 surfaces. The Ru12-Cu-porphyrin complex afforded positively charged Ru nanoparticles, which would provide high activity toward aromatic hydrogenation.
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Nishida,S. et al.
, p. 939 - 942 (1967)
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Water-soluble carbene complexes as catalysts for the hydrogenation of acetophenone under hydrogen pressure
Syska, Hitrisia,Herrmann, Wolfgang A.,Kühn, Fritz E.
, p. 56 - 62 (2012)
The synthesis of water-soluble Rh(I), Ir(I), and Ru(II) N-heterocyclic carbene complexes is described. These complexes are applied as catalysts for aqueous phase hydrogenation reactions. Good hydrogenation activities under ca. 40 atm pressure H2/sub
Active hydrogenation Rh nanocatalysts protected by new self-assembled supramolecular complexes of cyclodextrins and surfactants in water
Thanh Chau, Nguyet Trang,Menuel, Stéphane,Colombel-Rouen, Sophie,Guerrero, Miguel,Monflier, Eric,Philippot, Karine,Denicourt-Nowicki, Audrey,Roucoux, Alain
, p. 108125 - 108131 (2016)
The stability of inclusion complexes between randomly methylated β-cyclodextrin (RaMeCD) or its leucine-grafted analogue (RaMeCDLeu) with two hydroxylated ammonium surfactants was investigated. The binding isotherms and complexation constants were measured using the Isothermal Titration Calorimetry (ITC) technique. These host-guest inclusion complexes were used as protective agents during the formation of rhodium(0) nanoparticles by chemical reduction of rhodium trichloride in water. The amount of protective agent was adjusted in order to ensure both stability and reactivity of the rhodium nanocatalysts under the catalytic conditions. The size and dispersion of air-stable and water-soluble rhodium suspensions were determined by Transmission Electron Microscopy (TEM) analyses. These spherical nanoparticles, with sizes between 1.20 to 1.50 nm according to the nature of inclusion complexes, were evaluated in the biphasic hydrogenation of various reducible compounds (olefins, linear or aromatic ketones), showing promising results in terms of activity and selectivity.
Aromatic ring hydrogenation catalysed by nanoporous montmorillonite supported Ir(0)-nanoparticle composites under solvent free conditions
Das, Prabin,Sarmah, Podma Pollov,Borah, Bibek Jyoti,Saikia, Lakshi,Dutta, Dipak Kumar
, p. 2850 - 2855 (2016)
Ir(0)-nanoparticles (Ir-NPs) were synthesized into the nanopores of modified montmorillonite clay by incipient wetness impregnation of IrCl3 followed by reduction with ethylene glycol. The activation of the montmorillonite clay was carried out by treatment with HCl under controlled conditions to increase the surface area by generating nanopores which act as host for the metal nanoparticles. The synthesized Ir-NP-montmorillonite composites were characterized by N2-sorption, powder XRD, SEM, EDS, TEM, XPS, etc. The composites exhibit high surface area of 327 m2 g-1 and the Ir-NPs with size around 4 nm are uniformly distributed on the support. The Ir-NPs show efficient catalytic activity in aromatic ring hydrogenation under solvent free conditions with maximum conversion up to 100% and Turn Over Frequency (TOF) up to 79 h-1. The catalyst can be easily separated by simple filtration and remained active for several runs without significant loss of catalytic efficiency.
Synthesis, characterization, and reactivity of Cp*Rh(III) complexes having functional N,O chelate ligands
Munjanja, Lloyd,Yuan, Hongmei,Brennessel, William W.,Jones, William D.
, p. 28 - 32 (2017)
Cp*Rh(III) complexes 1a and 1b (Cp* = 1, 2, 3, 4, 5-pentamethylcyclopentadienyl) having functional N,O chelate ligands have been synthesized and characterized by 1H, 13C{1H} NMR spectroscopy, elemental analysis, IR spectroscopy and X-ray diffraction. Reactivity of these complexes has been investigated towards dehydrogenation of alcohols and hydrogenation of ketones. It was found that these compounds are precursors to the formation of Rh nanoparticles which serve as catalysts, as evidenced by mercury poisoning of the catalysis and direct observation of the particles by TEM, EDX, and XRD.
Nickel(0)-catalyzed three-component connection reaction of dimethylzinc, 1,3-dienes, and carbonyl compounds
Kimura, Masanari,Matsuo, Shintaro,Shibata, Kazufumi,Tamaru, Yoshinao
, p. 3386 - 3388 (1999)
Linear 1:1:1 coupling of dimethylzinc, 1,3-dienes, and carbonyl compounds in this order is facilitated by catalytic amounts of [Ni(acac)2] to give (E)-3-hexen-1-ols in good yields under mild conditions [Eq. (a)]. Increasing steric hindrance at the carbonyl group favors formation of the 1:2:1 adduct, and this is the sole product when the carbonyl compound is acetone, acac = acetylacetonate.
Aza versus Oxophilicity of SmI2: A Break of a Paradigm
Maity, Sandeepan,Flowers, Robert A.,Hoz, Shmaryahu
, p. 17070 - 17077 (2017)
Ligands that coordinate to SmI2 through oxygen are prevalent in the literature and make up a significant portion of additives employed with the reagent to perform reactions of great synthetic importance. In the present work a series of spectroscopic, calorimetric and kinetic studies demonstrate that nitrogen-based analogues of many common additives have a significantly higher affinity for Sm than the oxygen-based counterparts. In addition, electrochemical experiments show that nitrogen-based ligands significantly enhance the reducing power of SmI2. Overall, this work demonstrates that the use of nitrogen-based ligands provides a useful alternative approach to enhance the reactivity of reductants based on SmII.
Role of NaBH4 stabilizer in the oxazaborolidine-catalyzed asymmetric reduction of ketones with BH3-THF
Nettles, Shawn M.,Matos, Karl,Burkhardt, Elizabeth R.,Rouda, Dave R.,Corella, Joseph A.
, p. 2970 - 2976 (2002)
When stabilized BH3-THF (BTHF) was added to a mixture of ketone and tetrahydro-1-methyl-3,3-diphenyl-1H,3H-pyrrolo[1,2-c] [1,3,2]oxazaborole (MeCBS-ozaxaborolidine, MeCBS) catalyst 1, low enantioselectivities resulted. Several relative rate experiments showed that a borohydride species in BTHF catalyzed the nonselective borane reduction of ketones, effectively competing with enantioselective MeCBS reduction of ketones, lowering the overall selectivity of the reaction. Improved enantioselectivities in the reaction are obtained by reversing the mode of addition (ketone to BTHF and catalyst), lowering the concentration of NaBH4 stabilizer in the BTHF solution (87- 95% ee) and increasing the concentration or addition rate of BTHF. Decreased reaction temperature and increased catalyst loading only slightly improved the selectivity of the reaction. Upon reaction parameter optimization, simultaneous addition of substrate and BTHF to MeCBS catalyst stabilizer resulted in the highest overall enantioselectivities (96% ee) and diminished the effect of the borohydride. Alternatively, the addition of Lewis acids such as BF3-THF to the reaction mixture effectively destroyed the NaBH4 stabilizer in BTHF solutions, restoring the enantioselectivity to acceptable levels.
Selective hydrosilylation of ketones catalyzed by in situ -generated iron NHC complexes
Buitrago, Elina,Zani, Lorenzo,Adolfsson, Hans
, p. 748 - 752 (2011)
Aryl alkyl-, heteroaryl alkyl- and dialkyl ketones were readily reduced to their corresponding secondary alcohols in high yields, using the commercially available and inexpensive polymeric silane polymethylhydrosiloxane (PMHS), as reducing agent. The reaction is catalyzed by an in situ-generated iron complex, conveniently generated from iron(II) acetate and the commercially available N-heterocyclic carbene (NHC) precursor IPr·HCl.
Selective Hydrogenation of Aromatic Ketone over Pt@Y Zeolite through Restricted Adsorption Conformation of Reactants by Zeolitic Micropores
Chen, Qiang,Kang, Haozhe,Liu, Xuan,Jiang, Kun,Bi, Yunfei,Zhou, Yiming,Wang, Mengyue,Zhang, Meng,Liu, Lei,Xing, Enhui
, p. 1948 - 1952 (2020)
With thermodynamically favorable prevailing flat-lying adsorption of aromatic ketone molecules on Pt/Y catalyst via π-electron interaction, the 100 % selective hydrogenation toward aromatic alcohols is hardly achieved because of competitive hydrogenation on benzene rings. Here we developed a general method to prepare encapsulated Pt nanoparticles into Y Zeolite (Pt@Y), which provided a novel method to retard hydrogenation of benzene rings via thermodynamically unfavorable end-on adsorption conformation for almost 100 % selectivity from aromatic ketones to aromatic alcohols even at conversion close to 100 %.
Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
Oestreich, Martin,Seliger, Jan
supporting information, p. 247 - 251 (2020/10/29)
A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
supporting information, p. 5544 - 5553 (2021/02/05)
Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
