F:Highly flammable;
79-29-8Relevant articles and documents
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.
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.
Feinland et al.
, p. 991,992-994 (1961)
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.
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.
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.
