F:Highly flammable;
79-29-8Relevant academic research and scientific papers
A Large Isotope Effect on Formation of Tetramethylethylene Cations in γ-Irradiated 2,3-Dimethylbutane at 77 K. Tunneling of H2 Molecule
Miyazaki, Tetsuo,Kitamura, Susumu,Kozono, Yasusi,Matsunaga, Hiroaki
, p. 10767 - 10770 (1994)
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.
The partial hydrogenation of benzene to cyclohexene by nanoscale ruthenium catalysts in imidazolium ionic liquids
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
, p. 3734 - 3740 (2004)
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.
Catalytic olefin hydrogenation using N-heterocyclic carbene-phosphine complexes of iridium
Vazquez-Serrano, Leslie D.,Owens, Bridget T.,Buriak, Jillian M.
, p. 2518 - 2519 (2002)
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.
Boosting homogeneous chemoselective hydrogenation of olefins mediated by a bis(silylenyl)terphenyl-nickel(0) pre-catalyst
Lücke, Marcel-Philip,Yao, Shenglai,Driess, Matthias
, p. 2909 - 2915 (2021/03/14)
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.
Silylene-Bridged Tetranuclear Palladium Cluster as a Catalyst for Hydrogenation of Alkenes and Alkynes
Yanagisawa, Chikako,Yamazoe, Seiji,Sunada, Yusuke
, p. 169 - 173 (2020/10/29)
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.
Influence of Nitrate and Phosphate on Silica Fibrous Beta Zeolite Framework for Enhanced Cyclic and Noncyclic Alkane Isomerization
Hitam, Che Ku Nor Liana Che Ku,Izan, Siti Maryam,Jalil, Aishah Abdul,Nabgan, Walid
, p. 1723 - 1735 (2020/02/28)
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.
Tetraalkylammonium Functionalized Hydrochars as Efficient Supports for Palladium Nanocatalysts
Duarte, Tiago A. G.,Favier, Isabelle,Pradel, Christian,Martins, Luísa M. D. R. S.,Carvalho, Ana P.,Pla, Daniel,Gómez, Montserrat
, p. 2295 - 2303 (2020/03/23)
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.
Generalized Chemoselective Transfer Hydrogenation/Hydrodeuteration
Wang, Yong,Cao, Xinyi,Zhao, Leyao,Pi, Chao,Ji, Jingfei,Cui, Xiuling,Wu, Yangjie
supporting information, p. 4119 - 4129 (2020/08/10)
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.).
Highly Active Superbulky Alkaline Earth Metal Amide Catalysts for Hydrogenation of Challenging Alkenes and Aromatic Rings
Eyselein, Jonathan,F?rber, Christian,Grams, Samuel,Harder, Sjoerd,Knüpfer, Christian,Langer, Jens,Martin, Johannes,Thum, Katharina,Wiesinger, Michael
supporting information, p. 9102 - 9112 (2020/03/30)
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.
Mononuclear iron complex and organic synthesis reaction using same
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Page/Page column 32; 34, (2019/08/20)
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.)
