- A Large Isotope Effect on Formation of Tetramethylethylene Cations in γ-Irradiated 2,3-Dimethylbutane at 77 K. Tunneling of H2 Molecule
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The significant isotope effect on hydrogen elimination reaction from 2,3-dimethylbutane (h-DMB) cations was studied by ESR at 77 K.When a h-DMB-SF6 (0.6 mol percent) mixture is γ-irradiated at 70 K, h-DMB+ ions in addition to h-DMB radicals are produced.When the irradiated mixture is stored at 77 K for 10 min, tetramethylene (TME) cations are produced by H2 elimination from h-DMB+ ions.The rate constant for the H2 elimination reaction was measured as 1.1*1E-3 S-1 at 77 K.When a 2,3-dimethylbutane-2,3-D2 (d-DMB)-SF6 (0.6 molpercent) mixture is γ-irradiated at 70 K and then stored at 77 K, TME+ ions are scarcely produced upon the storage of the irradiated mixture at 77 K even for 5 days.The rate constant for the D2 elimination reaction from d-DMB+ ions was measured as 6.5*1E-8 s-1, which is much smaller than the rate constant for the H2 elimination reaction.The significant isotope effect on the reactions was explained in terms of a model of the tunnaeling elimination of a hydrogen molecule from a DMB+ ion.
- Miyazaki, Tetsuo,Kitamura, Susumu,Kozono, Yasusi,Matsunaga, Hiroaki
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- The partial hydrogenation of benzene to cyclohexene by nanoscale ruthenium catalysts in imidazolium ionic liquids
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The controlled decomposition of an Ru0 organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI·PF6), tetrafluoroborate (BMI·BF4) or trifluoromethane sulfonate (BMI·CF3SO3) ionic liquids with H2 represents a simple and efficient method for the generation of Ru0 nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of ≈57 nm that contain dispersed Ru0 nanoparticles with diameters of 2.6 ± 0.4 run. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75°C). The ternary diagram (benzene/cyclohexene/ BMI·PF6) indicated a maximum of 1% cyclohexene concentration in BMI·PF6, which is attained with 4% benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI·PF6. Selectivities of up to 39% in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2% in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.
- Silveira, Edson T.,Umpierre, Alexandre P.,Rossi, Liane M.,Machado, Giovanna,Morais, Jonder,Soares, Gabriel V.,Baumvol, Israel J. R.,Teixeira, Sergio R.,Fichtner, Paulo F. P.,Dupont, Jairton
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- Catalytic olefin hydrogenation using N-heterocyclic carbene-phosphine complexes of iridium
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N-heterocyclic carbene-phosphine complexes of iridium have been synthesized and examined for their performance in the catalytic homogeneous hydrogenation of a range of olefins; the reaction was further explored using parahydrogen induced polarization (PHIP) 1H NMR.
- Vazquez-Serrano, Leslie D.,Owens, Bridget T.,Buriak, Jillian M.
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- Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
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The isolable chelating bis(N-heterocyclic silylenyl)-substituted terphenyl ligand [SiII(Terp)SiII] as well as its bis(phosphine) analogue [PIII(Terp)PIII] have been synthesised and fully characterised. Their reaction with Ni(cod)2(cod = cycloocta-1,5-diene) affords the corresponding 16 VE nickel(0) complexes with an intramolecularη2-arene coordination of Ni, [E(Terp)E]Ni(η2-arene) (E = PIII, SiII; arene = phenylene spacer). Due to a strong cooperativity of the Si and Ni sites in H2activation and H atom transfer, [SiII(Terp)SiII]Ni(η2-arene) mediates very effectively and chemoselectively the homogeneously catalysed hydrogenation of olefins bearing functional groups at 1 bar H2pressure and room temperature; in contrast, the bis(phosphine) analogous complex shows only poor activity. Catalytic and stoichiometric experiments revealed the important role of the η2-coordination of the Ni(0) site by the intramolecular phenylene with respect to the hydrogenation activity of [SiII(Terp)SiII]Ni(η2-arene). The mechanism has been established by kinetic measurements, including kinetic isotope effect (KIE) and Hammet-plot correlation. With this system, the currently highest performance of a homogeneous nickel-based hydrogenation catalyst of olefins (TON = 9800, TOF = 6800 h?1) could be realised.
- Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
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p. 2909 - 2915
(2021/03/14)
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- Silylene-Bridged Tetranuclear Palladium Cluster as a Catalyst for Hydrogenation of Alkenes and Alkynes
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A planar tetranuclear palladium cluster was obtained from the reaction of a cyclotetrasilane with [Pd(CNtBu)2]3. Single-crystal X-ray diffraction analysis and DFT calculations revealed that the tetranuclear framework of the cluster was supported effectively by the bridging organosilylene ligand. Although [Pd(CNtBu)2]3 as well as mononuclear palladium bis(silyl) complex, cis-Pd(SiMePh2)2(CNtBu)2, do not act as the effective catalyst, the planar tetranuclear palladium cluster acts as an efficient catalyst for the hydrogenation of alkenes and alkynes including sterically hindered tri- and tetra-substituted alkenes.
- Yanagisawa, Chikako,Yamazoe, Seiji,Sunada, Yusuke
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p. 169 - 173
(2020/10/29)
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- Influence of Nitrate and Phosphate on Silica Fibrous Beta Zeolite Framework for Enhanced Cyclic and Noncyclic Alkane Isomerization
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Phosphate and nitrate were loaded on silica BEA (P/HSi?BEA and N/HSi?BEA), which is fibrously protonated by the impregnation method for n-hexane and cyclohexane isomerization. The characterization analysis specified the removal of tetrahedral aluminum atoms in the framework, which was triggered by the existence of phosphate and nitrate groups in the catalyst. The exchanged role of Si(OH)Al to P-OH as active acidic sites in the P/HSi?BEA catalyst reduced its acidic strength, which was confirmed by the FTIR results. Lewis acidic sites of P/HSi?BEA performance are a significant part in the generation of high protonic acid sites, as proven by the in situ ESR study. However, FTIR evacuation and 27Al NMR revealed that the reduction in the amount of extraframework Al (EFAl) is due to its interaction with the nitrate group on the outside of the catalyst surface. The N/HSi?BEA catalyst exhibited high acidic strength because of the existence of more Si(OH)Al, which was initiated during the nitrate-incorporation process. Of significance is that the catalytic performance of n-hexane isomerization in the presence of hydrogen reached 50.3% product isomer yield at 250 °C, which might be ascribed to the presence of P-OH active sites that are responsible for accepting electrons, forming active protonic acid sites. NO3-EFAl interaction induced the formation of Br?nsted acid sites, and higher mesopore volume favors the production of cyclohexane isomers up to 48.4% at 250 °C. This fundamental study exhibits that significant interactions given by such phosphate and nitrate groups with the unique silica fibrous BEA support could enhance isomerization, which contributes to the high quality of fuel.
- Hitam, Che Ku Nor Liana Che Ku,Izan, Siti Maryam,Jalil, Aishah Abdul,Nabgan, Walid
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p. 1723 - 1735
(2020/02/28)
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- Tetraalkylammonium Functionalized Hydrochars as Efficient Supports for Palladium Nanocatalysts
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With the aim of preparing bio-sourced supports with enhanced properties in catalysis, we devised an original strategy allowing the immobilization of metal nanoparticles. Thus, size-controlled hydrochars with a high degree of hydroxyl functionalities, from both neat sucrose or modified with acrylic acid (10 wt.%), were derivatized with ether linkers containing ammonium groups. These non-porous carbon-based materials were used as suitable supports for the immobilization of palladium nanoparticles. The catalytic materials were synthesized by reduction of Pd(OAc)2 to Pd(0) under H2 atmosphere in the presence of the corresponding hydrochar, and fully characterized by standard methods. Among the different hydrochar-supported palladium materials, those functionalized with tetraalkylammonium groups afforded heterogeneous catalysts, exhibiting high activity in hydrogenations of different types of substrates (alkynes, alkenes, and carbonyl and nitro derivatives). The most efficient catalyst was recycled up to ten runs without loss of catalytic behavior, in agreement with the unchanged composite materials after catalysis (Transmission Electron Microscopy (TEM) analyses) and the lack of metal leaching in the extracted organic products (no palladium detected by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES)); these systems exhibited enhanced recyclability properties as compared to commercial Pd/C catalyst.
- Duarte, Tiago A. G.,Favier, Isabelle,Pradel, Christian,Martins, Luísa M. D. R. S.,Carvalho, Ana P.,Pla, Daniel,Gómez, Montserrat
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p. 2295 - 2303
(2020/03/23)
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- Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
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A generalized, simple and efficient transfer hydrogenation of unsaturated bonds has been developed using HBPin and various proton reagents as hydrogen sources. The substrates, including alkenes, alkynes, aromatic heterocycles, aldehydes, ketones, imines, azo, nitro, epoxy and nitrile compounds, are all applied to this catalytic system. Various groups, which cannot survive under the Pd/C/H2 combination, are tolerated. The activity of the reactants was studied and the trends are as follows: styrene'diphenylmethanimine'benzaldehyde'azobenzene'nitrobenzene'quinoline'acetophenone'benzonitrile. Substrates bearing two or more different unsaturated bonds were also investigated and transfer hydrogenation occurred with excellent chemoselectivity. Nano-palladium catalyst in situ generated from Pd(OAc)2 and HBPin extremely improved the TH efficiency. Furthermore, chemoselective anti-Markovnikov hydrodeuteration of terminal aromatic olefins was achieved using D2O and HBPin via in situ HD generation and discrimination. (Figure presented.).
- Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
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supporting information
p. 4119 - 4129
(2020/08/10)
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- Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
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Two series of bulky alkaline earth (Ae) metal amide complexes have been prepared: Ae[N(TRIP)2]2 (1-Ae) and Ae[N(TRIP)(DIPP)]2 (2-Ae) (Ae=Mg, Ca, Sr, Ba; TRIP=SiiPr3, DIPP=2,6-diisopropylphenyl). While monomeric 1-Ca was already known, the new complexes have been structurally characterized. Monomers 1-Ae are highly linear while the monomers 2-Ae are slightly bent. The bulkier amide complexes 1-Ae are by far the most active catalysts in alkene hydrogenation with activities increasing from Mg to Ba. Catalyst 1-Ba can reduce internal alkenes like cyclohexene or 3-hexene and highly challenging substrates like 1-Me-cyclohexene or tetraphenylethylene. It is also active in arene hydrogenation reducing anthracene and naphthalene (even when substituted with an alkyl) as well as biphenyl. Benzene could be reduced to cyclohexane but full conversion was not reached. The first step in catalytic hydrogenation is formation of an (amide)AeH species, which can form larger aggregates. Increasing the bulk of the amide ligand decreases aggregate size but it is unclear what the true catalyst(s) is (are). DFT calculations suggest that amide bulk also has a noticeable influence on the thermodynamics for formation of the (amide)AeH species. Complex 1-Ba is currently the most powerful Ae metal hydrogenation catalyst. Due to tremendously increased activities in comparison to those of previously reported catalysts, the substrate scope in hydrogenation catalysis could be extended to challenging multi-substituted unactivated alkenes and even to arenes among which benzene.
- Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
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supporting information
p. 9102 - 9112
(2020/03/30)
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- Mononuclear iron complex and organic synthesis reaction using same
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A mononuclear iron bivalent complex having iron-silicon bonds, which is represented by formula (1), can exhibit an excellent catalytic activity in at least one reaction selected from three reactions, i.e., a hydrosilylation reaction, a hydrogenation reaction and a reaction for reducing a carbonyl compound. (In the formula, R1 to R6 independently represent a hydrogen atom, an alkyl group which may be substituted by X, or the like; X represents a halogen atom, or the like; L1 represents at least one two-electron ligand selected from an isonitrile ligand, an amine ligand, an imine ligand, a nitrogenated heterocyclic ring, a phosphine ligand, a phosphite ligand and a sulfide ligand, wherein, when multiple L1's are present, two L1's may be bonded to each other; L2 represents a two-electron ligand that is different from a CO ligand or the above-mentioned L1, wherein, when multiple L2's are present, two L2's may be bonded to each other; and m1 represents an integer of 1 to 4 and m2 represents an integer of 0 to 3, wherein the sum total of m1 and m2 (i.e., m1+m2) satisfies 3 or 4.)
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Page/Page column 32; 34
(2019/08/20)
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- Mechanistic Characterization of (Xantphos)Ni(I)-Mediated Alkyl Bromide Activation: Oxidative Addition, Electron Transfer, or Halogen-Atom Abstraction
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Ni(I)-mediated single-electron oxidative activation of alkyl halides has been extensively proposed as a key step in Ni-catalyzed cross-coupling reactions to generate radical intermediates. There are four mechanisms through which this step could take place: oxidative addition, outer-sphere electron transfer, inner-sphere electron transfer, and concerted halogen-atom abstraction. Despite considerable computational studies, there is no experimental study to evaluate all four pathways for Ni(I)-mediated alkyl radical formation. Herein, we report the isolation of a series of (Xantphos)Ni(I)-Ar complexes that selectively activate alkyl halides over aryl halides to eject radicals and form Ni(II) complexes. This observation allows the application of kinetic studies on the steric, electronic, and solvent effects, in combination with DFT calculations, to systematically assess the four possible pathways. Our data reveal that (Xantphos)Ni(I)-mediated alkyl halide activation proceeds via a concerted halogen-atom abstraction mechanism. This result corroborates previous DFT studies on (terpy)Ni(I)- and (py)Ni(I)-mediated alkyl radical formation, and contrasts with the outer-sphere electron transfer pathway observed for (PPh3)4Ni(0)-mediated aryl halide activation. This study of a model system provides insight into the overall mechanism of Ni-catalyzed cross-coupling reactions and offers a basis for differentiating electrophiles in cross-electrophile coupling reactions.
- Diccianni, Justin B.,Katigbak, Joseph,Hu, Chunhua,Diao, Tianning
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supporting information
p. 1788 - 1796
(2019/01/26)
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- Tailoring the structure and acid site accessibility of mordenite zeolite for hydroisomerisation of n-hexane
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Mordenite zeolites with diffusion-restricted access to the acid sites located in mono-dimensional 12-ring channels and 8-ring side pockets have found broad applications as catalysts for hydroisomerisation of linear C5 and C6 alkanes and other highly relevant acid-catalysed processes. The accessibility of the porous structure of mordenite (MOR) zeolite is traditionally enhanced by dealumination, but this is invariably connected with a dramatic reduction in the aluminium content and corresponding concentration of the acid sites in the zeolites. Here we describe the preparation of MOR zeolite with high micropore volume, three-dimensional supermicropores (d ~ 7.5 ?) and good acid site accessibility by concurrent extraction of Si and Al using postsynthesis fluorination-alkaline-acid treatment. The concurrent extraction of Si and Al enables formation of more developed supermicroporous structure and preservation of the molecular Si/Al. The procedure yields MOR with a crystalline structure in which the Si/Al ratio and the micropore volume can be tailored (Si/Al from ~ 6, VMI up to 0.25 cm3.g?1) by the chemical conditions of the treatment. The Al-rich 3D supermicroporous structure with accessible Br?nsted and Lewis active sites provides strongly enhanced activity, selectivity and long-term catalytic stability in the transformation of n-hexane into the corresponding branched isomers.
- Pastvova, Jana,Pilar, Radim,Moravkova, Jaroslava,Kaucky, Dalibor,Rathousky, Jiri,Sklenak, Stepan,Sazama, Petr
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p. 159 - 172
(2018/06/14)
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- Mononuclear ruthenium complex and organic synthesis reaction using same
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A neutral or cationic mononuclear ruthenium divalent complex represented by formula (1) can actualize exceptional catalytic activity in at least one reaction among a hydrosilylation reaction, hydrogenation reaction, and carbonyl compound reduction reaction. (In the formula, R1-R6 each independently represent a hydrogen atom or an alkyl group, aryl group, aralkyl group, organooxy group, monoorganoamino group, diorganoamino group, monoorganophosphino group, diorganophosphino group, monoorganosilyl group, diorganosilyl group, triorganosilyl group, or organothio group optionally substituted by X; at least one pair comprising any of R1-R3 and any of R4-R6 together represents a crosslinkable substituent; X represents a halogen atom, organooxy group, monoorganoamino group, diorganoamino group, or organothio group; L each independently represent a two-electron ligand other than CO and thiourea ligands; two L may bond to each other; and m represents an integer of 3 or 4.)
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Page/Page column 42; 46
(2018/03/26)
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- Air-Stable α-Diimine Nickel Precatalysts for the Hydrogenation of Hindered, Unactivated Alkenes
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Treatment of a mixture of air-stable nickel(II) bis(octanoate), Ni(O2CC7H15)2, and α-diimine ligand, iPrDI or CyADI (iPrDI = [2,6-iPr2-C6H3N=C(CH3)]2, CyADI = [C6H11N=C(CH3)]2) with pinacolborane (HBPin) generated a highly active catalyst for the hydrogenation of hindered, essentially unfunctionalized alkenes. A range of tri- and tetrasubstituted alkenes was hydrogenated and a benchtop procedure for the hydrogenation of 1-phenyl-1-cyclohexene on a multigram scale was demonstrated and represents an advance in catalyst activity and scope for the nickel-catalyzed hydrogenation of this challenging class of alkenes. Deuteration of 1,2-dimethylindene with the in situ-generated nickel catalyst with iPrDI exclusively furnished the 1,2-syn-d2-dimethylindane. With cyclic trisubstituted alkenes, such as 1-methyl-indene and methylcyclohexene, deuteration with the in situ generated nickel catalyst under 4 atm of D2 produced multiple deuterated isotopologues of the alkanes, signaling chain running processes that are competitive with productive hydrogenation. Stoichiometric studies, titration, and deuterium labeling experiments identified that the borane reagent served the dual role of reducing nickel(II) bis(carboxylate) to the previously reported nickel hydride dimer [(iPrDI)NiH]2 and increasing the observed hydrogenation activity. Performing the catalyst activation procedure with D2 gas and HBPin generated both HD and DBPin, establishing that the borane is involved in H2 activation as judged by 1H and 11B nuclear magnetic resonance spectroscopies.
- Léonard, Nadia G.,Chirik, Paul J.
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p. 342 - 348
(2018/01/17)
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- [(NHC)CoR2]: pre-catalysts for homogeneous olefin and alkyne hydrogenation
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A novel synthesis for dialkyl cobalt compounds [(tmeda)CoR2] is presented. In these complexes tmeda is readily replaced by an NHC or a bidentate phosphine ligand to form 3- and 4-coordinate compounds, respectively. [(ItBu)Co(CH2SiMe3)2] (ItBu = 1,3-di-tert-butylimidazolin-2-ylidene) serves as an efficient, homogeneous olefin hydrogenation pre-catalyst and allows the preparation of the novel cobalt bis(alkyne) complex [(ItBu)Co(η2-PhCCPh)2].
- Enachi, Andreea,Baabe, Dirk,Zaretzke, Marc-Kevin,Schweyen, Peter,Freytag, Matthias,Raeder, Jan,Walter, Marc D.
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supporting information
p. 13798 - 13801
(2018/12/14)
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- Disilaruthena- and Ferracyclic Complexes Containing Isocyanide Ligands as Effective Catalysts for Hydrogenation of Unfunctionalized Sterically Hindered Alkenes
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Disilaferra- and disilaruthenacyclic complexes containing mesityl isocyanide as a ligand, 3′ and 4′, were synthesized and characterized by spectroscopy and crystallography. Both 3′ and 4′ showed excellent catalytic activity for the hydrogenation of alkenes. Compared with iron and ruthenium carbonyl analogues, 1′ and 2′, the isocyanide complexes 3′ and 4′ were more robust under the hydrogenation conditions, and were still active even at higher temperatures (~80 °C) under high hydrogen pressure (~20 atm). The iron complex 3′ exhibited the highest catalytic activity toward hydrogenation of mono-, di-, tri-, and tetrasubstituted alkenes among currently reported iron catalysts. Ruthenium complex 4′ catalyzed hydrogenation under very mild conditions, such as room temperature and 1 atm of H2. The remarkably high catalytic activity of 4′ for hydrogenation of unfunctionalized tetrasubstituted alkenes was especially notable, because it was comparable to the activity of iridium complexes reported by Crabtree and Pfaltz, which are catalysts with the highest activity in the literature. DFT calculations suggested two plausible catalytic cycles, both of which involved activation of H2 assisted by the metal-silicon bond through σ-bond metathesis of late transition metals (oxidative hydrogen migration). The linear structure of M C≡N - C (ipso carbon of the mesityl group) played an essential role in the efficient hydrogenation of sterically hindered tetrasubstituted alkenes.
- Sunada, Yusuke,Ogushi, Hajime,Yamamoto, Taiji,Uto, Shoko,Sawano, Mina,Tahara, Atsushi,Tanaka, Hiromasa,Shiota, Yoshihito,Yoshizawa, Kazunari,Nagashima, Hideo
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supporting information
p. 4119 - 4134
(2018/03/29)
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- STABILIZATION OF ACTIVE METAL CATALYSTS AT METAL-ORGANIC FRAMEWORK NODES FOR HIGHLY EFFICIENT ORGANIC TRANSFORMATIONS
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Metal-organic framework (MOFs) compositions based on post?synthetic metalation of secondary building unit (SBU) terminal or bridging OH or OH2 groups with metal precursors or other post-synthetic manipulations are described. The MOFs provide a versatile family of recyclable and reusable single-site solid catalysts for catalyzing a variety of asymmetric organic transformations, including the regioselective boryiation and siiylation of benzyiic C—H bonds, the hydrogenation of aikenes, imines, carbonyls, nitroarenes, and heterocycles, hydroboration, hydrophosphination, and cyclization reactions. The solid catalysts can also be integrated into a flow reactor or a supercritical fluid reactor.
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Paragraph 0335; 0338
(2019/01/07)
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- Dual Rh?Ru Catalysts for Reductive Hydroformylation of Olefins to Alcohols
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An active and selective dual catalytic system to promote domino hydroformylation–reduction reactions is described. Apart from terminal, di- and trisubstituted olefins, for the first time the less active internal C?C double bond of tetrasubstituted alkenes can also be utilized. As an example, 2,3-dimethylbut-2-ene is converted into the corresponding n-alcohol with high yield (90 %) as well as regio- and chemoselectivity (>97 %). Key for this development is the use of a combination of Rh complexes with bulky monophosphite ligands and the Ru-based Shvo's complex. A variety of aromatic and aliphatic alkenes can be directly used to obtain mainly linear alcohols.
- Rodrigues, Fábio M. S.,Kucmierczyk, Peter K.,Pineiro, Marta,Jackstell, Ralf,Franke, Robert,Pereira, Mariette M.,Beller, Matthias
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p. 2310 - 2314
(2018/07/31)
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- Superior activity of non-interacting close acidic protons in Al-rich Pt/H-*BEA zeolite in isomerization of n-hexane
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Skeletal isomerization of linear alkanes, an essential reaction for the production of gasoline, relies on environmentally questionable chlorinated catalysts, whose activity exceeds that of alternative zeolite catalysts. This work describes an attempt to understand relations between the local arrangement of active sites and skeletal isomerization of n-hexane in order to adapt the structure of zeolite catalysts to increase the reaction rates. For this purpose, we used a combination of synthesis of zeolites of*BEA structural topology with unique density and distribution of strongly acid sites, analysis of the nature of the acid sites by1H MAS NMR spectroscopy and FTIR spectroscopy of the OH groups and adsorbed d3-acetonitrile, UV–vis-NIR spectroscopy of carbocations formed by protonization, and kinetic analysis. We demonstrate that the high density of non-interacting but close and strongly acidic structural hydroxyl groups significantly lower the activation barrier in the isomerization reaction compared to far-distant acid sites. The organotemplate-free synthesized Al-rich Pt/H-*BEA zeolite (Si/Al 4.2) with an unparalleled high concentration of the non-interacting close H+ions balancing the charge of the Al-Si-Al sequences forming a wall between the two channels yields 6 times higher reaction rates compared to state-of-the-art Si-rich Pt/H-zeolite catalysts.
- Sazama, Petr,Kaucky, Dalibor,Moravkova, Jaroslava,Pilar, Radim,Klein, Petr,Pastvova, Jana,Tabor, Edyta,Sklenak, Stepan,Jakubec, Ivo,Mokrzycki, Lukasz
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- Alkanethiolate-capped palladium nanoparticles for selective catalytic hydrogenation of dienes and trienes
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Selective hydrogenation of dienes and trienes is an important process in the pharmaceutical and chemical industries. Our group previously reported that the thiosulfate protocol using a sodium S-alkylthiosulfate ligand could generate catalytically active Pd nanoparticles (PdNP) capped with a lower density of alkanethiolate ligands. This homogeneously soluble PdNP catalyst offers several advantages such as little contamination via Pd leaching and easy separation and recycling. In addition, the high activity of PdNP allows the reactions to be completed under mild conditions, at room temperature and atmospheric pressure. Herein, a PdNP catalyst capped with octanethiolate ligands (C8 PdNP) is investigated for the selective hydrogenation of conjugated dienes into monoenes. The strong influence of the thiolate ligands on the chemical and electronic properties of the Pd surface is confirmed by mechanistic studies and highly selective catalysis results. The studies also suggest two major routes for the conjugated diene hydrogenation: the 1,2-addition and 1,4-addition of hydrogen. The selectivity between two mono-hydrogenation products is controlled by the steric interaction of substrates and the thermodynamic stability of products. The catalytic hydrogenation of trienes also results in the almost quantitative formation of mono-hydrogenation products, the isolated dienes, from both ocimene and myrcene.
- Chen, Ting-An,Shon, Young-Seok
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p. 4823 - 4829
(2017/10/19)
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- Alkene Hydrogenations by Soluble Iron Nanocluster Catalysts
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The replacement of noble metal technologies and the realization of new reactivities with earth-abundant metals is at the heart of sustainable synthesis. Alkene hydrogenations have so far been most effectively performed by noble metal catalysts. This study reports an iron-catalyzed hydrogenation protocol for tri- and tetra-substituted alkenes of unprecedented activity and scope under mild conditions (1–4 bar H2, 20 °C). Instructive snapshots at the interface of homogeneous and heterogeneous iron catalysis were recorded by the isolation of novel Fe nanocluster architectures that act as catalyst reservoirs and soluble seeds of particle growth.
- Gieshoff, Tim N.,Chakraborty, Uttam,Villa, Matteo,Jacobi von Wangelin, Axel
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supporting information
p. 3585 - 3589
(2017/03/21)
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- α-CAM mechanisms for the hydrogenation of alkenes by cis- and trans- disilametallacyclic carbonyl complexes (M = Fe, Ru, Os): Experimental and theoretical studies
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The hydrogenation of alkenes catalyzed by disilametallacyclic carbonyl complexes of iron, ruthenium or osmium was studied experimentally and theoretically. The disilaruthenacycle 2 with two CO ligands in the trans-configuration was prepared, characterized, and its ability to catalyze hydrogenation was studied. Similar to the corresponding iron analogue 1 in which the CO ligands are in the cis-configuration, 2 contains a H2MSi4 core with SiHSi SISHA (secondary interaction of silicon and hydrogen atoms) and catalyzed the hydrogenation of several alkenes under mild conditions. DFT calculations of 1 and 2 with cis- and trans-CO configurations (cis-1, trans-1, cis-2 and trans-2) revealed that the mechanism of ethylene hydrogenation comprises three catalytic cycles, and a key step involves the H-H bond of H2 being activated by an M-Si bond through oxidative hydrogen migration. These mechanisms are a variety of α-CAM (complex-assisted metathesis) mechanisms. Further calculations suggest that these catalytic cycles can apply to the catalytic hydrogenation of ethylene by osmium analogues of 1 and 2 (cis-3 and trans-3). Some of the elementary reactions in the cycles are dependent on the metal, and the osmium complexes show different performance from the iron and ruthenium analogues due to the characteristic natures of the third-row transition metals.
- Hoshi, Konoka,Tahara, Atsushi,Sunada, Yusuke,Tsutsumi, Hironori,Inoue, Ryoko,Tanaka, Hiromasa,Shiota, Yoshihito,Yoshizawa, Kazunari,Nagashima, Hideo
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p. 613 - 626
(2017/06/19)
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- Divalent Silicon-Assisted Activation of Dihydrogen in a Bis(N-heterocyclic silylene)xanthene Nickel(0) Complex for Efficient Catalytic Hydrogenation of Olefins
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The first chelating bis(N-heterocyclic silylene)xanthene ligand [SiII(Xant)SiII] as well as its Ni complexes [SiII(Xant)SiII]Ni(η2-1,3-cod) and [SiII(Xant)SiII]Ni(PMe3)2 were synthesized and fully characterized. Exposing [SiII(Xant)SiII]Ni(η2-1,3-cod) to 1 bar H2 at room temperature quantitatively generated an unexpected dinuclear hydrido Ni complex with a four-membered planar Ni2Si2 core. Exchange of the 1,3-COD ligand by PMe3 led to [SiII(Xant)SiII]Ni(PMe3)2, which could activate H2 reversibly to afford the first SiII-stabilized mononuclear dihydrido Ni complex characterized by multinuclear NMR and single-crystal X-ray diffraction analysis. [SiII(Xant)SiII]Ni(η2-1,3-cod) is a strikingly efficient precatalyst for homogeneous hydrogenation of olefins with a wide substrate scope under 1 bar H2 pressure at room temperature. DFT calculations reveal a novel mode of H2 activation, in which the SiII atoms of the [SiII(Xant)SiII] ligand are involved in the key step of H2 cleavage and hydrogen transfer to the olefin.
- Wang, Yuwen,Kostenko, Arseni,Yao, Shenglai,Driess, Matthias
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supporting information
p. 13499 - 13506
(2017/10/05)
-
- Supported Aluminum Catalysts for Olefin Hydrogenation
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Three-coordinate alkylaluminum sites were developed on a catechol-containing porous organic polymer support (CatPOP A2B1). The CatPOP-based alkylaluminum sites were characterized by solid-state attenuated total reflectance IR spectroscopy, 1H and 27Al magic-angle-spinning NMR spectroscopy, pair-distribution function X-ray absorption spectroscopy, and elemental analysis. The low-coordinate organoaluminum sites can hydrogenate and isomerize a range of mono- and disubstituted alkenes and alkynes under mild conditions (75-100 °C, 5-14 bar H2, 20 h). Results of experimental and computational mechanistic investigations suggest a heterolytic mechanism for the observed hydrogenation-isomerization activity.
- Camacho-Bunquin, Jeffrey,Ferrandon, Magali,Das, Ujjal,Dogan, Fulya,Liu, Cong,Larsen, Casey,Platero-Prats, Ana E.,Curtiss, Larry A.,Hock, Adam S.,Miller, Jeffrey T.,Nguyen, Sonbinh T.,Marshall, Christopher L.,Delferro, Massimiliano,Stair, Peter C.
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p. 689 - 694
(2017/05/31)
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- In Situ Generation and Immobilization of an Activated Rh Complex Catalyst in a Metal–Organic Framework for Hydrogenation at Low H2 Pressure
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Hydrogenation reactions under low-pressure H2 atmosphere are highly relevant from the safety viewpoint, because H2 gas is highly flammable in air and explosions can be triggered by spark, heat, or sunlight. In this work, an Rh complex/MOF hybrid was synthesized and used as catalyst for the hydrogenation of alkene substrates. Thanks to the activation of the Rh complex catalyst during the immobilization process and the intrinsic gas-condensation property of MOFs, the resulting composite showed much higher catalytic activity than the complex catalyst itself. Moreover, the composite can maintain its catalytic activity even at low H2 pressures that cannot support the reaction with the complex catalyst alone. Furthermore, in contrast to the complex catalyst, the composite maintained its catalytic activity even without solvent, and thus provides an environmentally friendly approach to catalysis.
- Takashima, Yohei,Fukuhara, Yoshimasa,Sato, Yasushi,Tsuruoka, Takaaki,Akamatsu, Kensuke
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p. 5344 - 5349
(2017/12/04)
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- Production of Gasoline Fuel from Alga-Derived Botryococcene by Hydrogenolysis over Ceria-Supported Ruthenium Catalyst
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Hydrogenolysis of hydrogenated botryococcene (Hy-Bot) was conducted over various supported Ru catalysts, Ir/SiO2, and Pt/SiO2–Al2O3. Ru/CeO2 with very high dispersion showed the highest yield (70 %) of gasoline-range (C5–C12) alkanes at 513 K. The main gasoline-range products were dimethylalkanes. This yield is comparable to or higher than the gasoline yields from botryococcene in the literature, which were obtained at much higher temperature. Ir/SiO2 also showed a high fuel yield, but the activity was much lower than that with the Ru catalysts. The reaction over Pt/SiO2–Al2O3 slowed down before total conversion of Hy-Bot was achieved. Ru/CeO2 was stable in the hydrogenolysis of Hy-Bot without loss of activity and selectivity during reuses. The carbon balance was low for the hydrogenolysis of Hy-Bot over all catalysts if the main products are heavy hydrocarbons, whereas for the hydrogenolysis of squalane the carbon balance was kept near 100 %. 1H NMR spectra of the product mixture and thermogravimetric analyses of the product mixture and the recovered catalyst revealed that the formation of aromatic compounds, polymeric products, and coke was negligible for the carbon balance. In a model reaction using substrate compounds with a substructure of Hy-Bot, only 2,5-dimethylhexane, which has a C6 chain with two Cprimary?Ctertiary bonds, produced a cyclic product, 1,4-dimethylcyclohexane, which has a higher boiling point than the substrate. This dehydrocyclization reaction makes the product distribution in the hydrogenolysis of Hy-Bot more complex.
- Nakaji, Yosuke,Oya, Shin-Ichi,Watanabe, Hideo,Watanabe, Makoto M.,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi
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p. 2701 - 2708
(2017/07/28)
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- Isomerization of n-hexane on binder-free shaped platinum-containing mordenite
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A catalyst has been prepared as binder-free shaped MOR-type zeolite in the H form promoted with 0.5 wt % platinum, and n-hexane conversion over this catalyst has been studied. It has been found that the selectivity for C4-C6 isoparaffins on the new catalyst is about 90% at 300°C, a feed space velocity of 1.5 h-1, and a hydrogen pressure of 3 MPa, with the hexane conversion being 80.0-83.0 wt % and the selectivity for isohexane making 83.0-86.0%. It has been shown that the new catalyst is stable for 50 h on-stream under these conditions.
- Travkina,Kuvatova,Pavlova,Ramadan, Ahmed Kanaan,Akhmetov,Kutepov
-
-
- Facile Synthesis, Characterization, and Catalytic Behavior of a Large-Pore Zeolite with the IWV Framework
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Large-pore microporous materials are of great interest to process bulky hydrocarbon and biomass-derived molecules. ITQ-27 (IWV) has a two-dimensional pore system bounded by 12-membered rings (MRS) that lead to internal cross-sections containing 14MRS. Investigations into the catalytic behavior of aluminosilicate (zeolite) materials with this framework structure have been limited until now due to barriers in synthesis. The facile synthesis of aluminosilicate IWV in both hydroxide and fluoride media is reported herein using simple, diquaternary organic structure-directing agents (OSDAs) that are based on tetramethylimidazole. In hydroxide media, a zeolite product with Si/Al=14.8-23.2 is obtained, while in fluoride media an aluminosilicate product with Si/Al up to 82 is synthesized. The material produced in hydroxide media is tested for the hydroisomerization of n-hexane, and results from this test reaction suggest that the effective pore size of zeolites with the IWV framework structure is similar to but slightly larger than that of ZSM-12 (MTW), in fairly good agreement with crystallographic data. Microporous materials: Synthesis of aluminosilicate IWV under industrially relevant conditions has been demonstrated, and the material can be produced in both fluoride and hydroxide media across a wide composition range. The zeolite demonstrates catalytic activity in the hydroisomerization of n-hexane (see figure).
- Schmidt, Joel E.,Chen, Cong-Yan,Brand, Stephen K.,Zones, Stacey I.,Davis, Mark E.
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p. 4022 - 4029
(2016/03/16)
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- Isomerization of n-hexane over Pt‐H3PW12O40/SBA-15 bifunctional catalysts: Effect of the preparation method on catalytic performance
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Pt-H3PW12O40 based bifunctional catalysts immobilized on SBA-15 were prepared either by mechanically mixing of acidic (HPW/SBA-15 or HPW@SBA-15) and metallic (Pt/SBA-15) monofunctional materials or by incorporation of the two active phases within the same composite using dual encapsulation (Pt@HPW@SBA-15) and encapsulation/impregnation (Pt/HPW@SBA-15) methodologies. The phase structure, chemical composition and surface physico-chemical properties were characterized in details by XRD, FT-IR, 31P MAS NMR, N2 adsorption‐desorption and HRTEM, STEM and EDX microscopy techniques. All hybrid materials showed highly ordered mesostructuration of the SBA-15 matrix with homogeneous dispersion of both metallic and HPW phases. In the case of the monophase bifunctional catalysts, Pt/HPW@SBA-15 and Pt@HPW@SBA-15, both functions were found to coexist in close vicinity, with the HPW crystallites mainly located in the silica walls whereas Pt was found either in the channels or as part of the walls depending on the preparation route. Their catalytic performance was then evaluated in the isomerization of n-hexane. The catalysts prepared by mechanical mixing exhibited higher activity than those where the Pt and HPW were integrated within a single solid. These results were interpreted by assuming that the carbocations in the latter case were hydrogenated faster on the Pt particles thus decreasing their preponderance at the steady-state compared to the mechanical mixture.
- Pinto, Teresa,Arquillière, Philippe,Dufaud, Véronique,Lefebvre, Frédéric
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-
- Deep hydrodesulfurization of FCC gasoline and gas oil cuts: Comparison of CO effect, a by-product from biomass
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Regarding the composition of the various feedstocks which should be hydrotreated in order to obtain fuels with amount of sulfur less than 10 wt ppm, we have shown that the presence of traces of CO, a by-product from lignocellulosic biomass feedstock conversion, inhibited the transformation of model compounds representative of FCC gasolines and gas oils over CoMo-based sulfide catalysts. Thus, this effect is more significant in the presence of 2-methylthiophene and 2,3-dimethylbut-2-ene representative of a FCC gasoline than in the presence of dibenzothiophene and 4,6-dimethyldibenzothiophene representative of a straight run gas oil, even if the operating conditions are not the same. This effect is attributed to phenomena of competitive adsorption between sulfur compounds, alkenes and CO on the catalyst surface.
- Pelardy, Florian,Philippe, Maxime,Richard, Frédéric,Daudin, Antoine,Devers, élodie,Hudebine, Damien,Brunet, Sylvette
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p. 1266 - 1275
(2016/10/13)
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- Metal-Organic Frameworks Stabilize Mono(phosphine)-Metal Complexes for Broad-Scope Catalytic Reactions
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Mono(phosphine)-M (M-PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal-organic framework (MOF) exhibited excellent activity in the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C-H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M-PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.
- Sawano, Takahiro,Lin, Zekai,Boures, Dean,An, Bing,Wang, Cheng,Lin, Wenbin
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supporting information
p. 9783 - 9786
(2016/08/19)
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- Sterically congested phosphonium borate acids as effective Br?nsted acid catalysts
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Phosphonium borate acids [HPPh2(C6F5)][B(C6F5)4] (2), [HPMes2(C6F5)][B(C6F5)4] (3) and [HPMes(C6F5)2][B(C6F5)4] (4) were synthesized via heterolytic dihydrogen cleavage in the presence of triisopropylsilylium and characterized by spectroscopic and crystallographic methods. Br?nsted acid catalysis using compounds 2–4 proved to be efficient for a number of challenging reactions (namely ionic hydrogenation, hydroamination and hydroarylation), owing to the restrained nucleophilicity of the sterically hindered conjugate bases. Reactivity of compounds 2–4 suggests that their pKavalues are similar to that of diethyl oxonium acid.
- Sinha, Arup,Jaiswal, Amit K.,Young, Rowan D.
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- Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations
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New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 106 and turnover frequencies of ~1.1 × 105 h-1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy?-)CoI(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.
- Zhang, Teng,Manna, Kuntal,Lin, Wenbin
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supporting information
p. 3241 - 3249
(2016/03/19)
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- Transition-Metal Oxos as the Lewis Basic Component of Frustrated Lewis Pairs
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The reaction of oxorhenium complexes that incorporate diamidopyridine (DAP) ligands with B(C6F5)3 results in the formation of classical Lewis acid-base adducts. The adducts effectively catalyze the hydrogenation of a variety of unactivated olefins at 100 °C. Control reactions with these complexes or B(C6F5)3 alone did not yield any hydrogenated products under these conditions. Mechanistic studies suggest a frustrated Lewis pair is generated between the oxorhenium DAP complexes and B(C6F5)3, which is effective at olefin hydrogenation. Thus, we demonstrate for the first time that the incorporation of a transition-metal oxo in a frustrated Lewis pair can have a synergistic effect and results in enhanced catalytic activity.
- Lambic, Nikola S.,Sommer, Roger D.,Ison, Elon A.
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supporting information
p. 4832 - 4842
(2016/05/09)
-
- Tetrahydroxydiboron-Mediated Palladium-Catalyzed Transfer Hydrogenation and Deuteriation of Alkenes and Alkynes Using Water as the Stoichiometric H or D Atom Donor
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There are few examples of catalytic transfer hydrogenations of simple alkenes and alkynes that use water as a stoichiometric H or D atom donor. We have found that diboron reagents efficiently mediate the transfer of H or D atoms from water directly onto unsaturated C-C bonds using a palladium catalyst. This reaction is conducted on a broad variety of alkenes and alkynes at ambient temperature, and boric acid is the sole byproduct. Mechanistic experiments suggest that this reaction is made possible by a hydrogen atom transfer from water that generates a Pd-hydride intermediate. Importantly, complete deuterium incorporation from stoichiometric D2O has also been achieved.
- Cummings, Steven P.,Le, Thanh-Ngoc,Fernandez, Gilberto E.,Quiambao, Lorenzo G.,Stokes, Benjamin J.
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supporting information
p. 6107 - 6110
(2016/06/09)
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- Rhodium Hydrogenation Catalysts Supported in Metal Organic Frameworks: Influence of the Framework on Catalytic Activity and Selectivity
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The cationic rhodium complexes (dppe)Rh(COD)BF4 and (MeCN)2Rh(COD)BF4 have been supported in metal-organic frameworks bearing anionic nodes (ZJU-28) and anionic linkers (MIL-101-SO3) via ion exchange. These MOF-supported Rh species serve as recyclable catalysts for the hydrogenation of both the terminal alkene substrate 1-octene and the internal alkene substrate 2,3-dimethylbutene. The nature of the MOF support impacts various aspects of catalysis, including: (i) the rate of 1-octene hydrogenation, (ii) the activity and recyclability of the catalyst in 2,3-dimethylbutene hydrogenation, and (iii) the size selectivity of hydrogenation with alkene substrates appended to calixarenes.
- Genna, Douglas T.,Pfund, Laura Y.,Samblanet, Danielle C.,Wong-Foy, Antek G.,Matzger, Adam J.,Sanford, Melanie S.
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p. 3569 - 3574
(2016/07/06)
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- Single-Site Cobalt Catalysts at New Zr8(μ2-O)8(μ2-OH)4 Metal-Organic Framework Nodes for Highly Active Hydrogenation of Alkenes, Imines, Carbonyls, and Heterocycles
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We report here the synthesis of robust and porous metal-organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M8(μ2-O)8(μ2-OH)4 and octahedral M6(μ3-O)4(μ3-OH)4. While the M6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M8-SBU is composed of eight MIV ions in a cubic fashion linked by eight μ2-oxo and four μ2-OH groups. The metalation of Zr-MTBC SBUs with CoCl2, followed by treatment with NaBEt3H, afforded highly active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.
- Ji, Pengfei,Manna, Kuntal,Lin, Zekai,Urban, Ania,Greene, Francis X.,Lan, Guangxu,Lin, Wenbin
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supporting information
p. 12234 - 12242
(2016/09/28)
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- SSZ-87: A borosilicate zeolite with unusually flexible 10-ring pore openings
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The structure of the as-synthesized borosilicate zeolite SSZ-87 has been solved by combining high-resolution X-ray powder diffraction (XPD) and rotation electron diffraction (RED) techniques. The unit cell and space group symmetry were found from the XPD data, and were essential for the initial analysis of the RED data. Although the RED data were only 15% complete, this proved to be enough for structure solution with the program Focus. The framework topology is the same as that of ITQ-52 (IFW), but for SSZ-87 the locations of the structure directing agent (SDA) and the B atoms could also be determined. SSZ-87 has large cages interconnected by 8- and 10-rings. However, results of hydroisomerization and Al insertion experiments are much more in line with those found for 12-ring zeolites. This prompted the structure analyses of SSZ-87 after calcination, and Al insertion. During calcination, the material is also partially deboronated, and the location of the resulting vacancies is consistent with those of the B atoms in the as-synthesized material. After Al insertion, SSZ-87 was found to contain almost no B and to be defect free. In its calcined and deboronated form, the pore system of SSZ-87 is more flexible than those of other 10-ring zeolites. This can be explained by the fact that the large cages in SSZ-87 are connected via single rather than double 10-ring windows and that there are vacancies in some of these 10-rings.
- Smeets, Stef,McCusker, Lynne B.,Baerlocher, Christian,Xie, Dan,Chen, Cong-Yan,Zones, Stacey I.
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p. 2015 - 2020
(2015/03/04)
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- The comparison of two classes of bifunctional SBA-15 supported platinum-heteropolyacid catalysts for the isomerization of n-hexane
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Mono- and bifunctional catalysts composed of silicotungstic acid (H4SiW12O40) and/or platinum nanoparticles supported on SBA-15 mesostructured silica were comparatively tested for the isomerization of n-hexane. Monofunctional catalysts were produced by impregnating the SBA-15 support with either H4SiW12O40 or the platinum particle precursor, H2PtCl6. In the bifunctional catalysts, both metallic and acidic functions were combined either by mechanically mixing the monofunctional solids yielding a multiphase bifunctional material (HSiW/SBA-15 + Pt/SBA-15), or by dual impregnation of H4SiW12O40 and Pt within a single material leading to the monophasic bifunctional catalyst, HSiW/Pt/SBA-15. These hybrid materials, with the exception of the monofunctional platinum catalyst, were all active for the gas-phase isomerization of n-hexane. The two bifunctional catalyst systems showed high activity and selectivity for branched isomers with no catalyst degradation over 3 days of reaction.
- Pinto, Teresa,Arquillière, Philippe,Niccolai, Gerald P.,Lefebvre, Frédéric,Dufaud, Véronique
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p. 5300 - 5308
(2015/07/07)
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- Effect of the doping agent nature on the characteristic and catalytic properties of aerogel zirconia catalysts doped with sulfate groups or heteropolytungstic acid
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Zirconia catalysts doped with sulfates or heteropolytungstic acid (HPW) prepared by sol-gel method and dried in supercritical conditions of solvent have been evaluated in n-hexane isomerization in the temperature range 150-220°C. Using HPW as dopant, the obtained catalyst is active at 220°C and selective towards isomers having higher Individual Octane Number, i.e., 2,2-DMB and 2,3-DMB compared with using sulfates as dopant. Based on N2-physisorption, XRD, SEM and TEM analyses, low specific area, particular morphology of grains and the lack of tetragonal ZrO2 particles reduce the adsorption of n-hexane reactant and led to inefficient catalyst throughout the temperature range 150-200°C. The catalyst doped with sulfur deactivates at T > 200°C since agglomerates of zirconia particles (TEM and SEM results) favor the coke formation. Using HPW, agglomerates of W oxide as well as phosphate groups (revealed by TGA, FTIR, EDX and UV/visible DRS) favor the formation of more valuable isomers at 220°C.
- Chakhari, Samir,Younes, Mohamed Kadri,Rives, Alain,Ghorbel, Abdelhamid
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- Phosphido- and Amidozirconocene Cation-Based Frustrated Lewis Pair Chemistry
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Methyl abstraction from neutral [Cp2ZrMe(ERR)] complexes 1 (E = N, P; R, R'; = alkyl, aryl) with either B(C6F5)3 or [Ph3C][B(C6F5)4] results in the formation of [Cp2Zr(ERR′)][X] complexes 2 (X- = MeB(C6F5)3-, B(C6F5)4-). The X-ray structure of amido complexes [Cp2Zr(NPh2)][MeB(C6F5)3] (2d) and [Cp2Zr(NtBuAr)][B(C6F5)4] (2e′, Ar = 3,5-C6H3(CH3)2) is reported, showing a sterically dependent Zr/N' interaction. Complexes 2 catalyze the hydrogenation of electron-rich olefins and alkynes under mild conditions (room temperature, 1.5 bar H2). Complex 2e binds CO2, giving [Cp2Zr(CO2)(NtBuAr)]2[MeB(C6F5)3]2 (3e). Amido complex 2d reacts with benzaldehyde yielding [Cp2Zr(OCH2Ph)((OC)PhNPh2)][MeB(C6F5)3] (7d). Phosphido complex [Cp2Zr(PCy2)][MeB(C6F5)3] (2a) reacts with diphenylacetylene to yield frustrated Lewis pair [Cp2Zr(PhCCPh)(PCy2)][MeB(C6F5)3] (8a) which further reacts with a range of carbonyl substrates.
- Normand, Adrien T.,Daniliuc, Constantin G.,Wibbeling, Birgit,Kehr, Gerald,Le Gendre, Pierre,Erker, Gerhard
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supporting information
p. 10796 - 10808
(2015/09/28)
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- Zirconium-Catalyzed Amine Borane Dehydrocoupling and Transfer Hydrogenation
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κ5-(Me3SiNCH2CH2)2N(CH2CH2NSiMe2CH2)Zr (1) has been found to dehydrocouple amine borane substrates, RR′NHBH3 (R = R′ = Me; R = tBu, R′ = H; R = R′ = H), at low to moderate catalyst loadings (0.5-5 mol %) and good to excellent conversions, forming mainly borazine and borazane products. Other zirconium catalysts, (N3N)ZrX [(N3N) = N(CH2CH2NSiMe2CH2)3, X = NMe2 (2), Cl (3), and OtBu (4)], were found to exhibit comparable activities to that of 1. Compound 1 reacts with Me2NHBH3 to give (N3N)Zr(NMe2BH3) (5), which was structurally characterized and features an η2 B-H σ-bond amido borane ligand. Because 5 is unstable with respect to borane loss to form 2, rather than β-hydrogen elimination, and 2-4 do not exhibit X ligand loss during catalysis, dehydrogenation is hypothesized to proceed via an outer-sphere-type mechanism. This proposal is supported by the catalytic hydrogenation of alkenes by 2 using amine boranes as the sacrificial source of hydrogen.
- Erickson, Karla A.,Stelmach, John P. W.,Mucha, Neil T.,Waterman, Rory
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p. 4693 - 4699
(2015/10/28)
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- MONONUCLEAR IRON COMPLEX AND ORGANIC SYNTHESIS REACTION USING SAME
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Provided is a mononuclear iron complex that comprises an iron-silicon bond that is represented by formula (1) and that exhibits excellent catalyst activity in each of a hydrosilylation reaction, a hydrogenation reaction, and reduction of a carbonyl compound. In formula (1), R 1 -R 6 either independently represent an alkyl group, an aryl group, an aralkyl group or the like that may be substituted with a hydrogen atom or X, or represent a crosslinking substituent in which at least one pair comprising one of R 1 -R 3 and one of R 4 -R 6 is combined. X represents a halogen atom, an organoxy group, or the like. L represents a two-electron ligand other than CO. When a plurality of L are present, the plurality of L may be the same as or different from each other. When two L are present, the two L may be bonded to each other. n and m independently represent an integer of 1 to 3 with the stipulation that n+m equals 3 or 4.
- -
-
Paragraph 0239-0241
(2016/12/01)
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- Cyclic bent allene hydrido-carbonyl complexes of ruthenium: Highly active catalysts for hydrogenation of olefins
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A new family of ruthenium complexes bearing the carbodicarbene-type ligand "cyclic bent allene" (CBA) have been synthesized from the common precursor RuHCl(CO)(PPh3)3. Complexes were evaluated for catalytic activity in the room-temperature hydrogenation of unactivated olefins and were found to be significantly more active than known ruthenium hydrido-carbonyl phosphine or NHC complexes. In particular, RuH(OSO2CF3)(CO)(SIMes)(CBA) was found to be among the most active hydrogenation catalysts, achieving comparable activity to Crabtree's catalyst in the hydrogenation of unactivated trisubstituted olefins and superior activity in the hydrogenation of styrene derivatives in side-by-side catalytic runs. RuH(OSO2CF3)(CO)(SIMes)(CBA) was also found to be highly active in olefin selective hydrogenation in the presence of a variety of unsaturated functional groups, and can achieve exceptional diastereoselectivity in functional-group-directed hydrogenations at very low catalyst loadings.
- Pranckevicius, Conor,Fan, Louie,Stephan, Douglas W.
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p. 5582 - 5589
(2015/05/13)
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- Transition metal nanoparticles stabilized by ammonium salts of hyperbranched polystyrene: effect of metals on catalysis of the biphasic hydrogenation of alkenes and arenes
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Abstract Hyperbranched polystyrene bearing ammonium salts (HPS-NR3+Cl-) behaves as an excellent stabilizer of ruthenium, rhodium, iridium, palladium, and platinum nanoparticles from 1 to 3 nm in size uniformly dispersed in the polymer matrix. The catalytic performance of the resulting metal-polymer composites, M@HPS-NR3+Cl-, is dependent on the metal. This dependence was investigated by assessing the hydrogenation of alkenes and arenes. The utility of M@HPS-NR3+Cl- as reusable catalysts in aqueous/organic biphasic systems was demonstrated by examining the catalysis of the hydrogenation of aromatic compounds containing various functional groups by Ru@HPS-NR3+Cl-.
- Gao, Lei,Kojima, Keisuke,Nagashima, Hideo
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supporting information
p. 6414 - 6423
(2015/08/18)
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- MONONUCLEAR RUTHENIUM COMPLEX AND ORGANIC SYNTHESIS REACTION USING SAME
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Provided is a mononuclear ruthenium complex that comprises a ruthenium-silicon bond that is represented by formula (1) and that exhibits excellent catalyst activity in each of a hydrosilylation reaction, a hydrogenation reaction, and reduction of a carbonyl compound. In formula (1), R 1 -R 6 either independently represent an alkyl group, an aryl group, an aralkyl group or the like that may be substituted with a hydrogen atom or X, or represent a crosslinking substituent in which at least one pair comprising one of R 1 -R 3 and one of R 4 -R 6 is combined. X represents a halogen atom, an organoxy group, or the like. L represents a two-electron ligand other than CO and phosphine. When a plurality of L are present, the plurality of L may be the same as or different from each other. When two L are present, the two L may be bonded to each other. n and m independently represent an integer of 1 to 3 with the stipulation that n+m equals 3 or 4.
- -
-
Paragraph 0212-0213; 0215
(2017/01/02)
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- Effect of acidic properties of mesoporous zeolites supporting Pt nanoparticles on hydrogenative conversion of methylcyclopentane
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The effect of acidic properties of mesoporous zeolites on the control of product selectivity during the hydrogenative isomerization of methylcyclopentane has been investigated. A series of mesoporous zeolites with controlled acidic properties were prepared by postdealumination process with hydrochloric acid under hydrothermal conditions, and the resultant zeolites used for supporting colloidal Pt nanoparticles (NPs) with a mean size of 2.5 nm (±0.6 nm). As compared to the pure Pt NPs supported on catalytically inert mesoporous silica (MCF-17) as the reference catalyst that can produce isomers most selectively (~80%), the Pt NPs supported on mesoporous zeolites produced C6-cyclic hydrocarbons (i.e., cyclohexane and benzene) most dominantly. The type and strength of the Br?nsted (B) and Lewis (L) acid sites of those zeolites with a controlled Al amount are analyzed by using FT-IR after the adsorption of pyridine and NH3 temperature-programmed desorption measurements, and they are correlated with the selectivity change between cyclohexane and benzene. From this investigation, we found a linear relationship between the number of Br?nsted acid sites and the formation rate for cyclohexane. In addition, we revealed that more Lewis acidic zeolite having relatively smaller B/L ratio is effective for the cyclohexane formation, whereas more Br?nsted acidic zeolite having relatively larger B/L ratio is effective for the benzene formation.
- Na, Kyungsu,Alayoglu, Selim,Ye, Rong,Somorjai, Gabor A.
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supporting information
p. 17207 - 17212
(2015/02/19)
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- Rhodium-catalyzed hydrogenation of olefins in γ-valerolactone-based ionic liquids
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γ-Valerolactone-based ionic liquids were successfully used as the catalyst phase for [Rh(cod)2][BF4]/RP(C6H 4-m-SO3Na)2 (R = Me, Pr, Bu, Cp) catalyzed hydrogenation of different olefins. Compared to broadly used ionic liquids e.g. 1-butyl-3-methylimidazolium chloride [bmim][Cl], the turnover frequencies were significantly higher and the reaction was selective for the CC double bonds in the presence of carbonyl, cyano, and phenyl groups. The catalyst was recycled for ten consecutive runs under regular or biphasic conditions without loss of activity. The vapour pressure and viscosity of γ-valerolactone-based ionic liquids were determined as well.
- Stradi, Andrea,Molnar, Mark,Ovari, Mihaly,Dibo, Gabor,Richter, Frank U.,Mika, Laszlo T.
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p. 1857 - 1862
(2013/09/24)
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- Metal-free HB(C6F5)2-catalyzed hydrogenation of unfunctionalized olefins and mechanism study of borane-mediated σ-bond metathesis
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Out with the metal: Metal-free hydrogenation of unfunctionalized olefins can be achieved by employing HB(C6F5)2 as the catalyst. The key step in the catalytic reaction is believed to involve a novel borane-mediated σ-bond metathesis, which has been investigated both experimentally and theoretically. Copyright
- Wang, Yuwen,Chen, Weiqiang,Lu, Zhenpin,Li, Zhen Hua,Wang, Huadong
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supporting information
p. 7496 - 7499
(2013/07/26)
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- Catalytic hydrogenation activity and electronic structure determination of bis(arylimidazol-2-ylidene)pyridine Cobalt Alkyl and Hydride Complexes
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The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, ( iPrCNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 C and 4 atm of H2 pressure, ( iPrCNC)CoCH3 is an effective precatalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene, and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, (iPrCNC)CoH, was accomplished by hydrogenation of (iPrCNC)CoCH3. Over the course of 3 h at 22 C, migration of the metal hydride to the 4-position of the pyridine ring yielded (4-H2-iPrCNC)CoN2. Similar alkyl migration was observed upon treatment of (iPrCNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redox-active, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic, and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2- ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity, and suggest that a wide family of pyridine-based pincers may also be redox-active.
- Yu, Renyuan Pony,Darmon, Jonathan M.,Milsmann, Carsten,Margulieux, Grant W.,Stieber, S. Chantal E.,Debeer, Serena,Chirik, Paul J.
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supporting information
p. 13168 - 13184
(2013/09/24)
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- Iridium(I) complexes with anionic N-heterocyclic carbene ligands as catalysts for the hydrogenation of alkenes in nonpolar media
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A series of lithium complexes of anionic N-heterocyclic carbenes that contain a weakly coordinating borate moiety (WCA-NHC) was prepared in one step from free N-heterocyclic carbenes by deprotonation with n-butyl lithium followed by borane addition. The reaction of the resulting lithium-carbene adducts with [M(COD)Cl]2 (M = Rh, Ir; COD = 1,5-cyclooctadiene) afforded zwitterionic rhodium(I) and iridium(I) complexes of the type [(WCA-NHC)M(COD)], in which the metal atoms exhibit an intramolecular interaction with the N-aryl groups of the carbene ligands. For M = Rh, the neutral complex [(WCA-NHC)Rh(CO)2] and the ate complex (NEt4)[(WCA-NHC) Rh(CO)2Cl] were prepared, with the latter allowing an assessment of the donor ability of the ligand by IR spectroscopy. The zwitterionic iridium-COD complexes were tested as catalysts for the homogeneous hydrogenation of alkenes, which can be performed in the presence of nonpolar solvents or in the neat alkene substrate. Thereby, the most active complex showed excellent stability and activity in hydrogenation of alkenes at low catalyst loadings (down to 10 ppm).
- Kolychev, Eugene L.,Kronig, Sabrina,Brandhorst, Kai,Freytag, Matthias,Jones, Peter G.,Tamm, Matthias
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supporting information
p. 12448 - 12459
(2013/09/23)
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- Catalyst design for iron-promoted reductions: An iron disilyl-dicarbonyl complex bearing weakly coordinating η2-(H-Si) moieties
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Iron disilyl dicarbonyl complex 1, in which two H-Si moieties of the 1,2-bis(dimethylsilyl)benzene ligand were coordinated to the iron center in an η2-(H-Si) fashion, was synthesized by the reaction of (η4-C6H8)Fe(CO)3 with 2 equiv. of 1,2-bis(dimethylsilyl)benzene under photo-irradiation. Complex 1 demonstrated high catalytic activity toward the hydrogenation of alkenes, the hydrosilylation of alkenes and the reduction of carbonyl compounds.
- Sunada, Yusuke,Tsutsumi, Hironori,Shigeta, Keisuke,Yoshida, Ryota,Hashimoto, Toru,Nagashima, Hideo
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supporting information
p. 16687 - 16692
(2013/12/04)
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- Iridium-catalyzed hydrosilylative reduction of glucose to hexane(s)
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In light of diminishing petroleum feedstocks, there is significant interest in developing carbohydrate defunctionalization reactions. In this context we have examined the use of iridium pincer catalysts for the hydrosilylative reduction of sugars, and we report herein complete reduction of silyl-protected glucose to a mixture of hexane isomers.
- McLaughlin, Matthew P.,Adduci, Laura L.,Becker, Jennifer J.,Gagné, Michel R.
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supporting information
p. 1225 - 1227
(2013/03/28)
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