- Iridium complexes of new NCP pincer ligands: Catalytic alkane dehydrogenation and alkene isomerization
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Iridium complexes of novel NCP pincer ligands containing pyridine and phosphinite arms have been synthesized. One Ir complex shows good catalytic activity for alkane dehydrogenation, and all complexes are highly active for olefin isomerization. A combination of the Ir complex and a (PNN)Fe pincer complex catalyzes the formation of linear alkylboronates selectively from internal olefins via sequential olefin isomerization-hydroboration. This journal is the Partner Organisations 2014.
- Jia, Xiangqing,Zhang, Lei,Qin, Chuan,Leng, Xuebing,Huang, Zheng
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- Photocatalytic properties of new cyclopentadienyl and indenyl rhodium(I) carbonyl complexes with water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) and tris(2-cyanoethyl)phosphine
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Reactions of [(η5-R)Rh(CO)2] (R = cp, ind) with water-soluble phosphines (L = 1,3,5-triaza-7-phosphaadamantane and tris(2-cyanoethyl)phosphine) give the new rhodium(I) complexes of the types [Rh(η5-cp)(CO)(PTA)] (1), [Rh(η5-cp)(CO)(P(CH 2CH2CN)3)] (2), [Rh(η5-ind)(CO) (PTA)] (3) and [Rh(η5-ind)(CO)(P(CH2CH 2CN)3)] (4) in isolated yields of 52-75%. All these compounds have been fully characterized by IR, 1H, 31P{1H} and 13C{1H} NMR, FAB-MS spectroscopies and elemental analyses. Reactivity for the substitution of phosphine is greater for [(η5-ind)Rh(CO)(L)] comparing to [(η5-cp)Rh(CO)(L)] because of a flexibility of the indenyl ligand to undergo facile η5-η3 coordinative isomerizations. The obtained complexes are active catalyst precursors for the dehydrogenation of propan-2-ol, octane and cyclooctane under photoassisted conditions without any organic hydrogen transfer acceptors, giving TOFs of 26-56 using 3 as precatalyst.
- Smoleński, Piotr
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- The First Successful Direct Metallation of Ethene
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Vinyl potassium was formed directly from ethene by use of a new butyl-lithium-potassium t-butoxide-tetramethylethylenediamine metallating reagent; typical products were obtained with 1-bromo-octane and after addition of LiBr in tetrahydrofuran, with benzaldehyde and diphenyl disulphide.
- Brandsma, Lambert,Verkruijsse, Hermann D.,Schade, Christian,Rague Schleyer, Paul von
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- Influence of elevated temperature and pressure on the chromium-catalysed tetramerisation of ethylene
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A catalyst system comprising a diphenylphosphineamine (PNP) ligand, chromium(III) acetylacetonate and a methylaluminoxane-based activator was studied for the selective tetramerisation of ethylene. The reaction was investigated over a broad temperature and pressure range and the resulting product mixture was interpreted in the light of the recently published, enlarged metallacycle mechanism. Vapour-liquid equilibrium (VLE) data were calculated for the binary ethylene-cyclohexane mixture over the relevant temperature and pressure ranges to deconvolute the influence of ethylene concentration and temperature. Good agreement of the experimental data with the proposed mechanism was found. Enlargement of the metallacycloheptane ring by insertion of ethylene was found to be dependent on the ethylene concentration, albeit to a lesser extent than assumed. The 1-octene selectivity, which reaches a maximum of 72-74 mass %, thus seems to be primarily dependent on the temperature. The formation of the cyclic side products methyl- and methylenecyclopentane was in effect independent of the ethylene concentration. This is in good accordance with the proposed mechanism, since it indicates that the formation of the products occurs via rearrangement of a metallacycle intermediate.
- Kuhlmann, Sven,Dixon, John T.,Haumann, Marco,Morgan, David H.,Ofili, Jimmy,Spuhl, Oliver,Taccardi, Nicola,Wasserscheid, Peter
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- Synthesis of Pincer Hydrido Ruthenium Olefin Complexes for Catalytic Alkane Dehydrogenation
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A series of new hydrido Ru(II) olefin complexes supported by isopropyl-substituted pincer ligands have been synthesized and characterized. These complexes are thermally robust and active for catalytic transfer and acceptorless alkane dehydrogenation. Notably, the alkane dehydrogenation catalysts are tolerant of a number of polar functional species.
- Zhang, Yuxuan,Fang, Huaquan,Yao, Wubing,Leng, Xuebing,Huang, Zheng
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- Highly active chromium-based selective ethylene tri-/tetramerization catalysts supported by N,N-diphospholylamines
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We have developed novel Cr(III) catalysts supported by asymmetic N,N-diphospholylamine ligands bearing a phenoxaphosphine group. Upon activation with MMAO-3A, the Cr(III) catalysts supported by the PNP ligands are highly active for ethylene tri-/tetramerization with considerable selectivity. The ligand substitution and oligomerization conditions are found to be essential to achieve high activity and controllable selectivity. The catalytic system with asymmetric diphospholylamine ligands exhibited higher activity than that supported by symmetric ligands. Asymmetric diphospholylamine ligand with a N-cyclohexyl group achieved the highest activity of 282.2?kg/(g?Cr/h) with a high total selectivity of 83.2% toward valuable 1-hexene (28.7%) and 1-octent (54.5%) at 35?bar under 80?°C.
- Ji, Xiaoyu,Song, Liubing,Zhang, Chengye,Jiao, Jiajun,Zhang, Jun
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- Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron–Ligand Cooperation in Concert
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The metal-free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal-free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron-ligand cooperation.
- Wech, Felix,Hasenbeck, Max,Gellrich, Urs
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- A NEW METHOD FOR THE in Situ GENERATION OF Cp2Zr(H)Cl (SCHWARTZ' REAGENT)
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Treatment of Cp2ZrCl2 with LiEt3BH in THF leads to formation of Cp2Zr(H)Cl.Subsequently introduced terminal acetylenes undergo hydrozirconation without compromising acid-sensitive functionality present in the alkyne.
- Lipshutz, Bruce H.,Keil, Robert,Ellsworth, Edmund L.
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- Switching a catalyst system from ethene polymerization to ethene trimerization with a hemilabile ancillary ligand
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A drastic ligand effect was observed in the catalytic ethene conversion by the substituted mono(cyclopentadienyl)titaniumtrichloride/methylalumoxane (MAO) catalysts shown. The catalyst with R = Me produces polyethene, whereas the catalyst with R = Ph selectively trimerizes ethene to 1-hexene. This switch in catalyst performance appears to be the result of a hemilabile behavior of the cyclopentadienyl ligand with the pendant arene group, involving reversible coordination of the arene moiety.
- Deckers, Patrick J. W.,Hessen, Bart,Teuben, Jan H.
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- Phospholane-Based Ligands for Chromium-Catalyzed Ethylene Tri- And Tetramerization
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Chromium complexes with bis(phospholane) ligands were synthesized and evaluated for ethylene tetramerization in a high-throughput reactor. Three ligand parameters - the phospholane substituent, the ligand backbone, and the type of phosphine (cyclic vs acyclic) - were investigated. The size of the phospholane substituent was found to impact the selectivity of the resulting catalysts, with smaller substituents leading to the production of larger proportions of 1-octene. Changing the ligand backbone from 1,2-phenylene to ethylene did not impact catalysis, but the use of acyclic phosphines in place of the cyclic phospholanes had a detrimental effect on catalytic activity. Selected phospholane-chromium complexes were evaluated in a 300 mL Parr reactor at 70 °C and 700 psi of ethylene pressure, and the ethylene oligomerization performance was consistent with that observed in the smaller, high-throughput reactor. MeDuPhos-CrCl3(THF) (MeDuPhos = 1,2-bis(2,5-dimethylphospholano)benzene; THF = tetrahydrofuran) gave activity and selectivity for 1-octene (54.8 wt %) similar to the state-of-the-art i-PrPNP-CrCl3(THF) (64.0 wt %) (PNP = bis(diphenylphosphino)amine), while EtDuPhos-CrCl3(THF) (EtDuPhos = 1,2-bis(2,5-diethylphospholano)benzene) exhibited even higher activity, with catalyst selectivity shifted toward 1-hexene production (90 wt %). These results are surprising, given the prevalence of the aryl phosphine motif in ligands used in ethylene oligomerization catalysts and the inferior performance of previously reported catalysts with alkyl phosphine-containing ligands.
- Boelter, Scott D.,Davies, Dan R.,Klosin, Jerzy,Margl, Peter,Milbrandt, Kara A.,Mort, Darrek,Rosen, Mari S.,Vanchura, Britt A.,Wilson, David R.,Wiltzius, Molly
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- CHEMISTRY OF ALKALI METAL TETRACARBONYLFERRATES. SYNTHESIS OF AMINES AND DEHALOGENATION REACTIONS BY A POLYMER SUPPORTED IRON CARBONYL COMPLEX
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The polymer-supported HFe(CO)4- can be easily prepared from potassium tetracarbonylhydridoferrate by an ion-exchange process with an ion-exchange resin (Amberlyst A 26) in its chloride form.It selectively reduces nitroarenes to amines, and reacts with 1,2-dibromoalkanes to give alkenes in good to excellent yields.
- Boldrini, Gian Paolo,Cainelli, Gianfranco,Umani-Ronchi, Achille
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- HYDROMETALLATION D'ALCYNES EN PRESENCE DE DERIVES DE CUIVRE(I)
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Reagents prepared from diisobutylalane (dibal) or tributylstannane and copper(I) species hydrometallate terminal alkynes in a syn way.
- Masure, D.,Coutrot, Ph.,Normant, J. F.
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- Kinetics of Reductions of Substituted Benzaldehydes with B-Alkyl-9-borabicyclononane (9-BBN)
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Second-order rate constants for the reaction of B-n-octyl-9-BBN with para-substituted benzaldehydes were obtained.Electron-withdrawing groups on the benzaldehyde increase the rate of reduction.The rate constants correlate with ?+ (ρ +1.03).Relative rates for reduction of para-substituted benzaldehydes with B-3-pinanyl-9-BBN gave a ρ of +0.49.The relative rates are consistent with a hydride addition to the carbonyl carbon in the rate-determining step.Activation parameters were obtained for the reaction of three benzaldehydes with B-n-octyl-9-BBN.The major barrier to the reaction is entropy.The large negative entropies of activation (-43 to -49 eu) indicate a highly ordered transition state.It is postulated that an organoborane-carbonyl oxygen complex is an intermediate in the reduction.
- Midland, M. Mark,Zderic, Stephen A.
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- Effect of Water on the Extraction and Reactions of Fluoride Anion by Quaternary Ammonium Phase-Transfer Catalysts
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The maximum conversion of the fluoride-chloride exchange reaction RCl + KF -> RF + KCl catalyzed by quaternary onium salts was found to be strongly dependent on the water content of the inorganic salt.A maximum conversion was obtained when the potassium fluoride contained 0.33 mol of water per mol of KF.This phenomenon is due to better extraction of the fluoride anion when the KF is drier, offset by decomposition of the catalyst in the absence of water.It was shown that the selectivity constant KselCl/F is dependent on composition of the inorganic salt and on temperature.Rate measurements indicate that the mechanism proposed by Starks for liquid-liquid exchange reactions is valid also in a solid-liquid process which is also chemically controlled.
- Dermeik, Salman,Sasson, Yoel
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- FLUORINATION BY USE OF TRANSITION METAL FLUORIDE-BIPYRIDINE COMPLEX IN APROTIC ORGANIC SOLVENTS
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Bipyridine complexes of transition metal fluorides which are soluble in aprotic organic sovents are used for the fluorination of organic halides under mild conditons.
- Sonoda, Hirosi,Sonoda, Takaaki,Kobayashi, Hiroshi
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- On the activation of Mo2B and MoB catalysts in oct-1-ene epoxidation with tert-butyl hydroperoxide
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The activation of Mo2B and MoB catalyst in the epoxidation of oct-1-ene with tert-butyl hydroperoxide is reported. The activation process is described by the Avraami-Erofeev topokinetic equation and includes two successive steps, viz.; the nucleation and formation of a new active phase. The epoxide is produced only when the activated form of the catalyst is involved. The effective and topochemical constants of the process have been determined.
- Nykypanchuk,Komarenskaya,Chernii
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- Stoichiometrically Activated Catalysts for Ethylene Tetramerization using Diphosphinoamine-Ligated Cr Tris(hydrocarbyl) Complexes
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A new, stoichiometric activation mode is presented for Cr-PNP (PNP = diphosphinoamine) complexes for ethylene tetramerization catalysis. To access suitable precatalysts, two robust Cr(III) multiaryl compounds were synthesized as THF adducts. These complexes are supported by a facially coordinated bis(aryl) ligand with an additional ether donor. From these precursors, Cr-PNP tris(hydrocarbyl) complexes were synthesized. Using 1 equiv of Br?nsted acid as an activator, an active species for the catalytic tetramerization of ethylene was produced, without the need for excess alkylaluminum reagents.
- Hirscher, Nathanael A.,Agapie, Theodor
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- Experimental and computational study of alkane dehydrogenation catalyzed by a carbazolide-based rhodium PNP pincer complex
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A rhodium complex based on the bis-phosphine carbazolide pincer ligand was investigated in the context of alkane dehydrogenation and in comparison with its iridium analogue. (carb-PNP)RhH2 was found to catalyze cyclooctane/t-butylethylene (COA/TBE) transfer dehydrogenation with a turnover frequency up to 10 min-1 and turnover numbers up to 340, in marked contrast with the inactive Ir analogue. TONs were limited by catalyst decomposition. Through a combination of mechanistic, experimental and computational (DFT) studies the difference between the Rh and Ir analogues was found to be attributable to the much greater accessibility of the 14-electron (carb-PNP)M(i) fragment in the case of Rh. In contrast, Ir is more strongly biased toward the M(iii) oxidation state. Thus (carb-PNP)RhH2 but not (carb-PNP)IrH2 can be dehydrogenated by sacrificial hydrogen acceptors, particularly TBE. The rate-limiting segment of the (carb-PNP)Rh-catalyzed COA/TBE transfer dehydrogenation cycle is found to be the dehydrogenation of COA. Within this segment, the rate-determining step is calculated to be (carb-PNP)Rh(cyclooctyl)(H) undergoing formation of a β-H agostic intermediate, while the reverse step (loss of a β-H agostic interaction) is rate-limiting for hydrogenation of the acceptors TBE and ethylene. Such a step has not previously been proposed as rate-limiting in the context of alkane dehydrogenation, nor, to our knowledge, has the reverse step been proposed as rate-limiting for olefin hydrogenation.
- Bézier, David,Guan, Changjian,Krogh-Jespersen, Karsten,Goldman, Alan S.,Brookhart, Maurice
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- An unprecedented α-olefin distribution arising from a homogeneous ethylene oligomerization catalyst
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Treatment of the bis(benzimidazolyl)amine chromium complex 2 with ethylene in the presence of MAO affords an exceptionally active oligomerization catalyst and an unprecedented distribution of 1-olefin products in which the C4n series is much more abundant than the C4n+2 series. Deuterium labeling studies are consistent with a metallacyclic chain growth mechanism in which the unusual product distribution arises from the interplay of two sites. Copyright
- Tomov, Atanas K.,Chirinos, Juan J.,Long, Richard J.,Gibson, Vernon C.,Elsegood, Mark R. J.
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- Catalytic Conversion of Alcohols. 15. Alkene Selectivity from the Conversion of 2-Ocatnol over Hafnium-Zirconium Mixed Oxide Catalysts
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The substitution of Zr ions for Hf does not alter the 1-octane selectivity from that of pure HfO2 until 0.70-0.85 mole fraction Zr, whereupon the selectivity abruptly changes to that of pure ZrO2.
- Davis, Burtron H.,Freeman, Garth B.,Watters, James C.,Collins, Dermot J.
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- Diesel-length aldehydes and ketones via supercritical Fischer Tropsch Synthesis on an iron catalyst
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Use of an iron-based catalyst (1 Fe:0.01 Cu:0.02 K by mole with and without 0.1 Zn) for Fischer Tropsch Synthesis with a supercritical hexanes reaction media resulted in a significant selectivity towards diesel-length aldehydes and methyl-ketones. Varying the residence time indicated that aldehydes are primary products that are converted by secondary reactions to olefins. Additionally, incorporation studies showed that octyl aldehyde and octyl alcohol incorporated into growing chains while the octyl olefin did not. The results of this work support n-alkanes and aldehydes as primary products, olefins as both primary and secondary products, CH4 and CO2 as secondary products, and an oxygenate mechanism for propagation.
- Durham, Ed,Zhang, Sihe,Roberts, Christopher
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- Catalytic Conversion of Alcohols Part 16. - Attempt to Correlate the ESCA Oxygen 1s Binding Energy with the Selectivity
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Neither the dehydration nor the terminal alkene selectivity for the conversion of secondary and tertiary alcohols over more than twenty metal oxide catalysts was related to the oxigen 1s binding energy of the catalyst.Even the attempt to correlate the selectivity to the oxigen 1s binding energy within a smaller group of metal oxide catalysts, Group IIIA or IVB, was not successful.
- Davis, Burtron H.,Russell, Sayra N.,Reucroft, Philip J.,Shalvoy, Richard B.
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- Graphdiyne-based Pd single-Atom catalyst for semihydrogenation of alkynes to alkenes with high selectivity and conversion under mild conditions
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The development of efficient heterogeneous catalysts for alkyne hydrogenation with high activity and selectivity is highly desirable and yet remains a great challenge. Herein, a Pd single-Atom catalyst (Pds-GDY) is prepared using graphdiyne as support, and used in the semihydrogenation of alkynes. As a proof of concept, the Pds-GDY exhibits a high activity for the semihydrogenation of phenylacetylene under mild reaction conditions, with a TOF of 6290 h-1, and a selectivity of 99.3% at 100% conversion, both much higher than those of the counterparts comprising Pd nanoparticles (NPs), namely, PdNP1-GDY (with 2 nm Pd NPs) and PdNP2-GDY (with 12 nm Pd NPs). In addition, after the full conversion of phenylacetylene, Pds-GDY could still maintain a selectivity as high as 98.9% towards styrene, with almost no phenylethane produced even with a prolonged reaction time; in contrast, for PdNP1-GDY and PdNP2-GDY, within the same reaction time, the selectivity decreases dramatically to 66.6% and 8.5%, respectively. Infrared spectroscopy reveals that Pds-GDY features the weakest adsorption to styrene, which is responsible for its high performance. This work provides an effective strategy to rationally design Pd catalysts for semihydrogenation of alkynes to alkenes with desirable activity and selectivity. This journal is
- Lu, Tong-Bu,Lu, Xiu-Li,Si, Rui,Tang, Shang-Feng,Wang, Hong-Juan,Yin, Xue-Peng,Zhang, Chao
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- Chemically induced dynamic nuclear polarization and the mechanism of the reaction of Et3Al with CCl4 in the presence of transition metal complexes
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Integral effects of chemically induced 1H and 13C nuclear polarization are reported for the reaction of Et3Al with CCl4 catalyzed by Pd(acac)2, Cu(acac)2, and Cp2TiCl2; for the reaction of (n-C8H 17)3Al with CCl4 in the absence of a catalyst and in the presence of Ni(acac)2; and for the reaction of the cyclic organoaluminum compound 1-ethyl-3-butylaluminacyclopentane with CCl4 in the presence of Pd(acac)2. A scheme of the catalytic cycle of this reaction predicting the formation of both radical and nonradical products is derived from the observed chemically induced dynamic nuclear polarization (CIDNP) effects and from data on the products of the reaction between Et 3Al and CCl4 in the presence of Pd(acac)2. According to the results of qualitative analysis of the CIDNP effects, the reactions of the trialkylalanes and the cyclic organoaluminum compound with CCl4 in the presence of various metal complexes proceeded via similar mechanisms.
- Sadykov,Safina,Teregulov,Paramonov
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- Towards selective ethylene tetramerization
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And the magic number is... . A large amount of oligomer-free 1-octene (99.9%) was produced from ethylene by a catalytic system based on chromium during the formation of polyethylene wax [see GC-MS chromatogram; the other three significant peaks are methanol (quenching agent), ethyl acetate (needle-rinsing agent), and toluene (solvent)]. Copyright
- Licciulli, Sebastiano,Thapa, Indira,Albahily, Khalid,Korobkov, Ilia,Gambarotta, Sandro,Duchateau, Robbert,Chevalier, Reynald,Schuhen, Katrin
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- WAVELENGTH-DEPENDENT PHOTOCHEMISTRY OF 2,3-DIMETHYL-2-BUTENE AND 2-OCTENE IN SOLUTION
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Direct irradiations of the title compounds were performed at 185, >200, >220, and 228 nm in hydrocarbon solvents.The evident wavelength dependence of the product distributions observed is of importance in specifying the excited state involved in the formation of each photoproduct, and suggests that more than two excited singlet states of an alkene undergo distinctly different photoreactions rather than suffer mutual conversions between the states.
- Inoue, Yoshihisa,Mukai, Toshio,Hakushi, Tadao
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- A Heterogeneous Metal-Free Catalyst for Hydrogenation: Lewis Acid–Base Pairs Integrated into a Carbon Lattice
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Designing heterogeneous metal-free catalysts for hydrogenation is a long-standing challenge in catalysis. Nanodiamond-based carbon materials were prepared that are surface-doped with electron-rich nitrogen and electron-deficient boron. The two heteroatoms are directly bonded to each other to form unquenched Lewis pairs with infinite π-electron donation from the surrounding graphitic structure. Remarkably, these Lewis pairs can split H2 to form H+/H? pairs, which subsequently serve as the active species for hydrogenation of different substrates. This unprecedented finding sheds light on the uptake of H2 across carbon-based materials and suggests that dual Lewis acidity–basicity on the carbon surface may be used to heterogeneously activate a variety of small molecules.
- Ding, Yuxiao,Huang, Xing,Yi, Xianfeng,Qiao, Yunxiang,Sun, Xiaoyan,Zheng, Anmin,Su, Dang Sheng
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- Alkali Metal O,O-Diethyl Phosphorotelluroates, a Reagent Class for Deoxygenation of Epoxides, Especially Terminal Epoxides
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Epoxides are deoxygenated to olefins by alkali metal O,O-diethyl phosphorotelluroates.These reagents can be used in stoichiometric quantities or they can be generated continuously in situ from tellurium under conditions that approach a catalytic nature with respect to the metal.Terminal epoxides are deoxygenated most readily, but the reaction does work for other types.In the case of epoxides formally derived from acyclic olefins, the Z compound reacts more easily than the E isomer and the deoxygenation is stereospecific. 1,2-Epoxycyclohexanes react faster than 1,2-epoxycyclopentanes.Selective deoxygenations, especially those in favor of terminal epoxides, are possible.
- Clive, Derrick L. J.,Menchen, Steven M.
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- 2-Benzimidazol-6-pyrazol-pyridine Chromium(III) Trichlorides: Synthesis, Characterization, and Application for Ethylene Oligomerization and Polymerization
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A series of chromium(III) complexes, LCrCl3 (Cr1-Cr4: L = 2-(N-R2-benzimidazol-2-yl)-6-(3,5-R1-pyrazol-1-yl)pyridine; Cr1: R1 = H, R2 = H; Cr2: R1 = Me, R2 = H; Cr3: R1 = Me, R2 = Me; Cr4: R1 = Me, R2 = Bn), were synthesized and characterized by IR spectroscopy and elemental analysis. The studies of the solid state of Cr2 and Cr3 revealed distorted octahedral geometries around the chromium centers by X-ray diffractions. In the presence of MAO, Cr1-Cr4 exhibited high activities toward ethylene oligomerization (up to 2.17 × 106 g·mol-1(Cr)·h-1) and ethylene polymerization (up to 6.78 × 105 g·mol-1(Cr)·h-1). The oligomers were produced with high selectivity for α-olefins (>99%), confirmed by FT-IR and 13C NMR, and the distributions followed the Schulz-Flory equation. Various reaction parameters including the amount of cocatalyst, reaction temperature, and time were evaluated in detail, and it was evident that the title complexes had good thermal stability and the substituents on imidazole-N of the ligands dramatically impacted the catalytic activities as well as the distribution of the products.
- Luo, Wenlong,Li, Antai,Liu, Shaofeng,Ye, Hongqi,Li, Zhibo
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- Diverse Reactivity of a Rhenium(V) Oxo Imido Complex: [2 + 2] Cycloadditions, Chalcogen Metathesis, Oxygen Atom Transfer, and Protic and Hydridic 1,2-Additions
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We present a wide range of reactivity studies focused on the rhenium(V) oxo imido complex (DippN)(O)Re(BDI) (1, Dipp = 2,6-diisopropylphenyl and BDI = N,N′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate). This complex, which was previously shown to possess a highly polarized Re oxo moiety, has proven to be a potent nucleophile and a valuable precursor to a variety of rare structural motifs in rhenium coordination complexes. For example, the Re oxo moiety of 1 undergoes [2 + 2] cycloadditions with carbodiimides, isocyanates, carbon dioxide, and isothiocyanates at room temperature. In the case of CO2, the cycloadduct with 1 (a carbonate complex) undergoes the facile ejection of CO2, demonstrating that this binding process is reversible. In the case of isothiocyanate, chalcogen metathesis with 1 takes place readily as the inclusion of a second equivalent of substrate in the reaction mixture rapidly yields a dithiocarbamate complex. This metathesis process was extended to the reactivity of 1 with phosphine chalcogenides, leading to the isolation of terminal sulfido imido and selenido imido complexes. Attempts to complete this series and generate the analogous terminal telluride led to the formation of a bidentate tritelluride (Te32-) complex. Triethylphosphine could only undergo oxygen atom transfer (OAT) with 1 under pressing thermal conditions that also led to C-N cleavage of the BDI ligand. In contrast, OAT between 1 and CO or 2,6-xylylisocyanide (XylNC) was found to be much more facile, proceeding within seconds at room temperature. While the addition of excess CO led to a rhenium(III) imido dicarbonyl complex, we found that the addition of 2 equiv of XylNC was necessary to promote OAT, resulting in the isolation of a rare example of a stable metal isocyanate complex. Our experimental observations of CO and XylNC and their OAT reactions with 1 inspired a mechanistic computational study to probe the intermediates and kinetic barriers along these reaction pathways. Finally, we describe 1,2-additions of both protic and hydridic substrates with the Re oxo moiety of 1, which most notably led to the syntheses of an uncommon example of a terminal rhenium hydroxide complex and an oxo-bridged Re-O-Zr hetero-bi-metallic complex that was generated using Schwartz's reagent (Cp2ZrHCl). A brief discussion of a potential alternative route to 1 is also presented.
- Arnold, John,Bergman, Robert G.,Cortes, Emmanuel A.,Fostvedt, Jade I.,Jain, Anukta,Lohrey, Trevor D.,Oanta, Alexander K.
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- Dehydration of 2-Octanol over Ca-doped CeO2 Catalysts
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Vapor-phase catalytic dehydration of 2-octanol was investigated over Ca-doped CeO2 at 375 °C and atmospheric pressure. Ca doping up to 0.15 wt % was found to increase the dehydration activity for 2-octanol, whereas further increases in Ca conte
- Gnanamani, Muthu Kumaran,Jacobs, Gary,Shafer, Wilson D.,Davis, Burtron H.
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- N,N-Diphospholylamines-A new family of ligands for highly active, chromium-based, selective ethene oligomerisation catalysts
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A series of new diphosphazane (PNP) ligands that contain 2,3,4,5-tetraethylphosphole or dibenzophosphole moieties has been synthesised. The new compounds have been screened for chromium-catalysed, selective ethene oligomerisation by insitu combination with CrCl3(thf)3 and methylaluminoxane (MAO). The ligands derived from 2,3,4,5-tetraethylphosphole produce highly active catalysts for ethene oligomerisation, which show excellent selectivity to C6 and C8 linear α-olefins. Complexes of the form [Cr(CO)4L] were synthesised and studied by IR spectroscopy and single-crystal XRD. Variable-temperature NMR spectroscopy was used to investigate restricted P=N rotation in compounds with bulky nitrogen substituents. Top hole phosphole! New diphosphazane ligands based on phosphole donors produce highly active catalysts with chromium for the selective oligomerization of ethene. Modification of the backbone nitrogen substituent gives excellent control over the C6/C8 selectivity. MAO=methylaluminoxane.
- Stennett, Tom E.,Hey, Thomas W.,Ball, Liam T.,Flynn, Stephanie R.,Radcliffe, James E.,Mcmullin, Claire L.,Wingad, Richard L.,Wass, Duncan F.
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- The Combination of Potassium Fluoride and Calcium Fluoride: A Useful Heterogeneous Fluorinating Reagent
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The combination of potassium fluoride and calcium fluoride was found to be an effective and practical solid reagent for the fluorination of various organic chlorides and bromides under mild conditions.
- Ichihara, Junko,Matsuo, Toshiya,Hanafusa, Terukiyo,Ando, Takashi
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- Unexpectedly selective hydrogenation of phenylacetylene to styrene on titania supported platinum photocatalyst under 385 nm monochromatic light irradiation
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Conversion of alkynes to alkenes by photocatalysis has inspired extensive interest, but it is still challenging to obtain both high conversion and selectivity. Here we first demonstrate the photocatalytic conversion of phenylacetylene (PLE) to styrene (STE) with both high conversion and selectivity by using the titania (TiO2) supported platinum (Pt) as photocatalyst under 385 nm monochromatic light irradiation. It is demonstrated that the conversion rate of PLE is strongly dependent on the content of Pt cocatalyst loaded on the surface of TiO2. Based on our optimization, the conversion of PLE and the selectivity towards STE on the 1 wt% Pt/TiO2 photocatalyst can unexpectedly reach as high as 92.4% and 91.3%, respectively. The highly selective photocatalytic hydrogenation can well be extended to the conversion of other typical alkynes to alkenes, demonstrating the generality of selective hydrogenation of C≡C over the Pt/TiO2 photocatalyst.
- Lian, Juhong,Chai, Yuchao,Qi, Yu,Guo, Xiangyang,Guan, Naijia,Li, Landong,Zhang, Fuxiang
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- Chromium-Based Ethylene Tetramerization Catalysts Supported by Silicon-Bridged Diphosphine Ligands: Further Combination of High Activity and Selectivity
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A series of silicon-bridged diphosphine (SBDP) ligands were synthesized and characterized. The Cr precatalyst supported by bis(diphenylphosphinomethyl)dimethylsilane achieved a high activity of 4.2×106 g (molCr h)?1 and a high selectivity of 78.44 % towards valuable 1-octene by using methylcyclohexane as the solvent at an ethylene pressure of 4.0 MPa and 45 °C. An intramolecular β-H transfer mechanism was proposed to explain the unequal molar proportions of cyclic C6 byproducts. The crystal structure data of two complexes proved that the SBDP system with a wide P?Cr?P bite angle could also exhibit superior performance in the tetramerization of ethylene.
- Zhang, Le,Meng, Xuejiao,Chen, Yanhui,Cao, Chengang,Jiang, Tao
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- Selective ethylene oligomerization in the presence of ZnR2: Synthesis of terminally-functionalized ethylene oligomers
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The selective oligomerization of ethylene to 1-hexene or 1-octene provides a selective route to these valuable α-olefins. Selective trimerization and tetramerization of ethylene with Cr catalysts have been proposed to occur by a mechanism involving metallacycle intermediates. We envisioned that the intermediacy of metallacycles could provide an opportunity to generate new classes of functionalized ethylene oligomers by chain transfer to a transmetalation reagent. Herein, we report the influence of transmetalation agents such as zinc alkyls on the selectivity of ethylene oligomerization with a Cr(PNP)Cl3/MAO system (PNP = Ph2PN(iPr) PPh2). Oligomerization of ethylene with Cr(PNP)Cl3/MAO at 200 psig of ethylene at 25 or 45 °C generates 1-hexene, 1-octene, C 10-C22 oligomers, and polyethylene. The addition of ZnR2 increases the productivity and selectivity for C 10-C22 oligomers and results in a decrease in the amount and molecular weight of the polyethylene generated. Analysis of the product distribution after quenching with D2O reveals that 1-hexene and 1-octene are unlabeled, but that all higher oligomers are deuteriated alkanes or alkenes, depending on the nature of the zinc alkyl (R = Me, Et, Bu). Mechanistic proposals are presented to explain the formation of differentially functionalized coproducts in the presence of zinc alkyls. These studies reveal that oligomerization in the presence of ZnR2 provides a new route to end-functionalized ethylene oligomers and new insights on the reactivity of metallacycle intermediates in the Cr-catalyzed oligomerization of ethylene.
- Son, Kyung-Sun,Waymouth, Robert M.
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- Thermal stability and water effect on ion-exchange resins in ethyl octyl ether production at high temperature
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Abstract Thermal stability and water inhibition effects were studied at 150 and 190 C on the chlorinated acidic polystyrene-divinylbenzene resins Amberlyst 70, Amberlyst XE804 and Purolite CT482, and the non-chlorinated one Dowex 50Wx2. Catalytic activity in the reaction between ethanol and 1-octanol to form ethyl octyl ether (EOE) was monitored for 70 h in a continuous fixed-bed reactor. Leaching of sulfonic groups at 190 C was found to be negligible for Purolite CT482 and Amberlyst 70, but it was significant for Amberlyst XE804 and Dowex 50Wx2. The activity decay to a steady EOE reaction rate on Purolite CT482 and Amberlyst 70 has been ascribed to the reaction rate inhibition by the formed water. However, water adsorption on the catalyst also modified the resin morphology during the course of the reaction. Adsorbed water swelled the gel-phase and more acid sites became accessible for 1-octanol molecules. As a result, the activity decay of EOE and the longer byproduct di-n-octyl ether syntheses was smaller than that of the shorter one diethyl ether.
- Guilera, Jordi,Ramírez, Eliana,Fité, Carles,Iborra, Montserrat,Tejero, Javier
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- LIGANDS FOR PRODUCTION OF 1-HEXENE IN CHROMIUM ASSISTED ETHYLENE OLIGOMERIZATION PROCESS
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Catalyst compositions and processes for the oligomerization of ethylene to 1-hexene are described. The catalyst composition includes a triamino bisphospino (NPNPN) ligand system with specific phosphorous and nitrogen ligands. The terminal nitrogen atoms include linear alkyl hydrocarbons that differ in the number of carbon atoms by 3.
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Paragraph 0054-0056
(2022/01/12)
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- Diverse Mechanistic Pathways in Single-Site Heterogeneous Catalysis: Alcohol Conversions Mediated by a High-Valent Carbon-Supported Molybdenum-Dioxo Catalyst
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With the increase in the importance of renewable resources, chemical research is shifting focus toward substituting petrochemicals with biomass-derived analogues and platform-molecule transformations such as alcohol processing. To these ends, in-depth mechanistic understanding is key to the rational design of catalytic systems with enhanced activity and selectivity. Here we discuss in detail the structure and reactivity of a single-site active carbon-supported molybdenum-dioxo catalyst (AC/MoO2) and the mechanism(s) by which it mediates alcohol dehydration. A range of tertiary, secondary, and primary alcohols as well as selected bio-based terpineols are investigated as substrates under mild reaction conditions. A combined experimental substituent effect/kinetic/kinetic isotope effect/EXAFS/DFT computational analysis indicates that (1) water assistance is a key element in the transition state; (2) the experimental kinetic isotopic effect and activation enthalpy are 2.5 and 24.4 kcal/mol, respectively, in good agreement with the DFT results; and (3) several computationally identified intermediates including Mo-oxo-hydroxy-alkoxide and cage-structured long-range water-coordinated Mo-dioxo species are supported by EXAFS. This structurally and mechanistically well-characterized single-site system not only effects efficient transformations but also provides insight into rational catalyst design for future biomass processes.
- Bedzyk, Michael J.,Das, Anusheela,Kratish, Yosi,Li, Jiaqi,Ma, Qing,Marks, Tobin J.
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p. 1247 - 1257
(2022/02/07)
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- Contra-thermodynamic Olefin Isomerization by Chain-Walking Hydroboration and Dehydroboration
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We report a dehydroboration process that can be coupled with chain-walking hydroboration to create a one-pot, contra-thermodynamic, short-or long-range isomerization of internal olefins to terminal olefins. This dehydroboration occurs by a sequence comprising activation with a nucleophile, iodination, and base-promoted elimination. The isomerization proceeds at room temperature without the need for a fluoride base, and the substrate scope of this isomerization is expanded over those of previous isomerizations we have reported with silanes.
- Bloomer, Brandon,Butcher, Trevor W.,Ciccia, Nicodemo R.,Conk, Richard J.,Hanna, Steven,Hartwig, John F.
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p. 1005 - 1010
(2022/02/10)
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- Steric and Electronic Effects of Phosphane Additives on the Catalytic Performance of Colloidal Palladium Nanoparticles in the Semi-Hydrogenation of Alkynes
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We report on the influence of phosphanes on the catalytic activity and selectivity of colloidal, tetraoctylammonium bromide (TOAB) stabilised palladium nanoparticles (NPs) in the semi-hydrogenation of alkynes to olefins. Full characterisation of the catalytic system (HRTEM, EDX, XPS, IR, NMR) confirmed the formation of spherical particles with a narrow size distribution (1.9±0.5 nm). The catalytic performance of the Pd NPs in the semi-hydrogenation of 1-octyne, 2-octyne and phenylacetylene to the respective olefins and the influences on the selectivity was investigated. The system shows high activities and selectivities at mild conditions (0 °C and 1.0 bar H2 pressure). It was shown that generally, phosphanes lead to an increase of both the reaction rate and selectivity towards the olefin where both steric and electronic effects of the ligand play a crucial role for the catalyst performance. A moderate steric demand of the ligand with a rather weak σ-donating ability turned out to give the highest catalytic performance.
- Staiger, Lena,Kratky, Tim,Günther, Sebastian,Tomanek, Ondrej,Zbo?il, Radek,Fischer, Richard W.,Fischer, Roland A.,Cokoja, Mirza
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p. 227 - 234
(2020/10/14)
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- Phosphorus and nitrogen-doped palladium nanomaterials support on coral-like carbon materials as the catalyst for semi-hydrogenation of phenylacetylene and mechanism study
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In this work, two types of polyporous and coral-like materials (CN) with high specific surface area are prepared using sodium glutamate as a carrier. At the same time, a CN-supported phosphorus-nitrogen-doped palladium nanomaterial CN-P-Pd is synthesized and applied to the preparation of styrene by selective hydrogenation of phenylacetylene under mild conditions. As shown in the TEM images, Pd nanoparticles with a particle size of about 4.4 nm are uniformly dispersed on the surface of the carrier. The results of N2 adsorption–desorption reveal that the surface area of the prepared catalyst (CN-P-Pd) is 1307 m2g?1. In addition, the experimental exploration shows the intervention of P in carbon-nitrogen materials can contribute to improve the selectivity of the reaction, which can be attributed to the fact that P element can change the electron density of Pd. Meanwhile, it is found that the solvent not only affects the activity of catalyst, but also the selectivity of the reaction. Kinetic study shows the activation energy of the reaction is 4.5 kJ/mol. With the increase of the reaction temperature, the dissolution rate of hydrogen in the solvent gradually slows down, which inhibits the progress of the reduction reaction. Mechanistic studies demonstrate that the carbon-nitrogen materials have strong adsorption capacity for substrates, and also provide more adsorption sites for phenylacetylene. Additionally, the optimal catalyst (CN-P-Pd) also has high reaction activity to other alkynes and the conversion can reach at 95%. Moreover, the optimal catalyst can be reused several times without significant reduction in reaction activity.
- Ma, Lei,Jiang, Pengbo,Wang, Kaizhi,Lan, Kai,Huang, Xiaokang,Yang, Ming,Gong, Li,Jia, Qi,Mu, Xiao,Xiong, Yucong,Li, Rong
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- Merging Halogen-Atom Transfer (XAT) and Cobalt Catalysis to Override E2-Selectivity in the Elimination of Alkyl Halides: A Mild Route towardcontra-Thermodynamic Olefins
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We report here a mechanistically distinct tactic to carry E2-type eliminations on alkyl halides. This strategy exploits the interplay of α-aminoalkyl radical-mediated halogen-atom transfer (XAT) with desaturative cobalt catalysis. The methodology is high-yielding, tolerates many functionalities, and was used to access industrially relevant materials. In contrast to thermal E2 eliminations where unsymmetrical substrates give regioisomeric mixtures, this approach enables, by fine-tuning of the electronic and steric properties of the cobalt catalyst, to obtain high olefin positional selectivity. This unprecedented mechanistic feature has allowed access tocontra-thermodynamic olefins, elusive by E2 eliminations.
- Zhao, Huaibo,McMillan, Alastair J.,Constantin, Timothée,Mykura, Rory C.,Juliá, Fabio,Leonori, Daniele
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supporting information
p. 14806 - 14813
(2021/09/18)
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- Reactions of Sodium Diisopropylamide: Liquid-Phase and Solid-Liquid Phase-Transfer Catalysis by N, N, N′, N″, N″-Pentamethyldiethylenetriamine
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Sodium diisopropylamide (NaDA) in N,N-dimethylethylamine (DMEA) and DMEA-hydrocarbon mixtures with added N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDTA) reacts with alkyl halides, epoxides, hydrazones, arenes, alkenes, and allyl ethers. Comparisons of PMDTA with N,N,N′,N′-tetramethylethylenediamine (TMEDA) accompanied by detailed rate and computational studies reveal the importance of the trifunctionality and κ2-κ3 hemilability. Rate studies show exclusively monomer-based reactions of 2-bromooctane, cyclooctene oxide, and dimethylresorcinol. Catalysis with 10 mol % PMDTA shows up to >30-fold accelerations (kcat > 300) with no evidence of inhibition over 10 turnovers. Solid-liquid phase-transfer catalysis (SLPTC) is explored as a means to optimize the catalysis as well as explore the merits of heterogeneous reaction conditions.
- Algera, Russell F.,Collum, David B.,Ma, Yun,Woltornist, Ryan A.
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supporting information
p. 13370 - 13381
(2021/09/03)
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- Pd, Cu and Bimetallic PdCu NPs Supported on CNTs and Phosphine-Functionalized Silica: One-Pot Preparation, Characterization and Testing in the Semi-Hydrogenation of Alkynes
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Triphenylphosphine stabilized Pd, Cu and PdCu nanocatalysts supported on carbon nanotubes (CNTs) or phosphorus functionalised silica (P?SiO2) were prepared via a one-pot methodology. The series of P?SiO2 supported catalysts evidenced metal particle sizes of metallic nanoparticles (M-NPs) between 1 and 2.4 nm, smaller than their equivalents on CNTs (2.4–2.6 nm). Such a difference in particle size as a function of the support and the metallic composition indicated the more pronounced mediation of the CNTs support during the formation of the M-NPs when compared to the P?SiO2 support. The series of supported catalysts were tested in the semi-hydrogenation of alkynes providing differences in reactivity which might be correlated with the size and composition of the M-NPs and the nature of corresponding support. The carbon supported catalysts displayed in general higher activities than those supported on silica and the bimetallic catalyst PdCu/CNTs were the most selective for the case of alkyl substituted alkynes. This catalyst could moreover be recycled several times without loss of activity nor selectivity.
- Sánchez-Resa, Daniel,Delgado, Jorge A.,Fernández-Martínez, Maria Dolores,Didelot, Chloé,De Mallmann, Aimery,Szeto, Ka? C.,Taoufik, Mostafa,Claver, Carmen,Godard, Cyril
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supporting information
p. 4970 - 4978
(2021/11/10)
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- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- Ni-Catalyzed Isomerization-Hydrocyanation Tandem Reactions: Access to Linear Nitriles from Aliphatic Internal Olefins
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A highly regioselective nickel-based catalyst system for the isomerization/hydrocyanation of aliphatic internal olefins is described. This benign tandem reaction provides facile access to a wide variety of aliphatic nitriles in good yields with excellent regioselectivities. Thanks to Lewis acid-free conditions, the protocol features board functional groups tolerance, including secondary amine and unprotected alcohol groups.
- Gao, Jihui,Ni, Jie,Yu, Rongrong,Cheng, Gui-Juan,Fang, Xianjie
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supporting information
p. 486 - 490
(2021/02/05)
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- The role of CO2 in the dehydrogenation of n-octane using Cr-Fe catalysts supported on MgAl2O4
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The effect of CO2 on the dehydrogenation of n-octane over Cr-Fe oxides supported on MgAl2O4 (MgAl) was investigated. Addition of Fe as a promoter facilitated the formation of Cr-O-Fe polymeric units, stabilizing the CrOx in the +3 state on the catalysts’ surface. Catalytic results revealed that the 2Cr-Fe catalyst was the most active and also stable (ca. 10 % CO2 conversion, 8 % n-octane conversion, 84 % selectivity to octene isomers) during a 30 h reaction. The stability and high octenes selectivity over this catalyst was reflected in its higher surface basicity. Based on a redox study using CO2, it was found that the dominant mechanism for CO2 activation was oxidative (Mars van Krevelen) over the monometallic Cr catalyst, while a non-oxidative (Reverse Water Gas Shift) mechanism applied over the nCr-Fe bimetallic catalysts. It is proposed that Cr-O-MgAl is the active site in the monometallic Cr catalyst, while the Cr-O-Fe polymeric units are the active sites in the bimetallic catalysts. Coke deposition was shown to be the major cause of deactivation of the catalysts.
- Adam, Dailami S.,Bala, Muhammad D.,Friedrich, Holger B.,Mahomed, Abdul S.
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- Piperazine-promoted gold-catalyzed hydrogenation: The influence of capping ligands
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Gold nanoparticles (NPs) combined with Lewis bases, such as piperazine, were found to perform selective hydrogenation reactions via the heterolytic cleavage of H2. Since gold nanoparticles can be prepared by many different methodologies and using different capping ligands, in this study, we investigated the influence of capping ligands adsorbed on gold surfaces on the formation of the gold-ligand interface. Citrate (Citr), poly(vinyl alcohol) (PVA), polyvinylpyrrolidone (PVP), and oleylamine (Oley)-stabilized Au NPs were not activated by piperazine for the hydrogenation of alkynes, but the catalytic activity was greatly enhanced after removing the capping ligands from the gold surface by calcination at 400 °C and the subsequent adsorption of piperazine. Therefore, the capping ligand can limit the catalytic activity if not carefully removed, demonstrating the need of a cleaner surface for a ligand-metal cooperative effect in the activation of H2 for selective semihydrogenation of various alkynes under mild reaction conditions.
- Barbosa, Eduardo C. M.,Camargo, Pedro H. C.,Fiorio, Jhonatan L.,Hashmi, A. Stephen K.,Kikuchi, Danielle K.,Rossi, Liane M.,Rudolph, Matthias
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p. 1996 - 2003
(2020/04/22)
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- Selective hydrogenation of terminal alkynes over palladium nanoparticles within the pores of amino-modified porous aromatic frameworks
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Palladium catalysts, based on porous aromatic frameworks, synthesized via Suzuki cross-coupling reaction and further modified with amino groups, were prepared and tested in hydrogenation of several unsaturated compounds. Catalysts obtained were characterized by several techniques including IR spectroscopy, solid-state NMR spectroscopy, low-temperature nitrogen adsorption, transmission electron microscopy, atomic emission spectroscopy and X-ray photoelectron spectroscopy. It was shown that the amino-groups within the structure of aromatic frameworks interact with palladium nanoparticles and enhance their selectivity towards hydrogenation of terminal alkynes.
- Karakhanov, Edward,Maximov, Anton,Terenina, Maria,Vinokurov, Vladimir,Kulikov, Leonid,Makeeva, Daria,Glotov, Aleksandr
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p. 176 - 184
(2019/05/24)
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- Creation of Redox-Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO-66 with Unique Semihydrogenation Catalytic Properties
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Semihydrogenation of alkynes to produce alkenes is very important in the industry; however, over-hydrogenation heavily complicates the postprocesses, which are highly energy consuming and not environmentally friendly. One of the most efficient pathways to solve this challenging issue is to develop highly selective catalysts that could only hydrogenate alkynes and are inactive in hydrogenation of alkenes. This work presents herein an efficient catalyst, consisting of in situ created PdS0.53 nanoparticles as the redox-active sites inside the defect pores of metal–organic framework UiO-66, which demonstrates very high alkene selectivity (up to 99.5%) in semihydrogenation of easily over-hydrogenated terminal alkynes. In contrast to the traditional catalysts, strict control over the reaction time becomes the nonessential condition because the catalyst system is almost inactive in hydrogenation of alkenes. Therefore, this paradigm work provides a practically applicable pathway for the development of efficient catalysts with unique catalytic properties for selective semihydrogenation reactions.
- Dong, Ming-Jie,Wang, Xuan,Wu, Chuan-De
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- Constructing PtI?COF for semi-hydrogenation reactions of phenylacetylene
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The great efforts have been devoted to fabricate excellent hydrogenation catalysts owing to the broad applications in industrial fields. However, the preparation processes of traditional hydrogenation catalysts are often complicated. Herein, mono-valence PtI?COF was synthesized as a catalyst for semi-hydrogenation of phenylacetylene for the first time. The easily prepared SO3H-linked COF possesses a two-dimensional eclipsed layered-sheet structure, making its incorporation with metal ions feasible. The as-prepared PtI?COF composite exhibits excellent performance for semi-hydrogenation phenylacetylene with 93.5% conversion and 90.2% selectivity to styrene under mild reaction conditions (1 ?bar H2, 25 ?°C) within 20 ?min. It's worth noting that the turnover frequency (TOF) value reaches at 3965 h-1, which outperforms most of recently reported excellent Pt-based catalysts for this reaction.
- Li, Jian Hong,Yu, Zhi Wu,Li, Jian Qiang,Fan, Ya Ling,Gao, Zhi,Xiong, Jian Bo,Wang, Li,Tao, Yuan,Yang, Li Xiao,Xiao, Yu Xin,Luo, Feng
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- Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks
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The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h?1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.
- Choe, Kwanghak,Li, Guodong,Qiu, Xueying,Ri, Myonghak,Shi, Xinghua,Tang, Zhiyong,Wang, Hui,Wang, Yinglong,Xue, Guangxin,Yuan, Yi,Zhao, Wenshi,Zheng, Fengbin
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supporting information
p. 3650 - 3657
(2020/02/04)
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- Migratory Hydrogenation of Terminal Alkynes by Base/Cobalt Relay Catalysis
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Migratory functionalization of alkenes has emerged as a powerful strategy to achieve functionalization at a distal position to the original reactive site on a hydrocarbon chain. However, an analogous protocol for alkyne substrates is yet to be developed. Herein, a base and cobalt relay catalytic process for the selective synthesis of (Z)-2-alkenes and conjugated E alkenes by migratory hydrogenation of terminal alkynes is disclosed. Mechanistic studies support a relay catalytic process involving a sequential base-catalyzed isomerization of terminal alkynes and cobalt-catalyzed hydrogenation of either 2-alkynes or conjugated diene intermediates. Notably, this practical non-noble metal catalytic system enables efficient control of the chemo-, regio-, and stereoselectivity of this transformation.
- Liu, Bingxue,Liu, Qiang,Liu, Xufang
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supporting information
p. 6750 - 6755
(2020/03/13)
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- Accelerating Chemo- And Regioselective Hydrogenation of Alkynes over Bimetallic Nanoparticles in a Metal-Organic Framework
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Selective semihydrogenation of alkynes has been a long-term and significant target, yet it remains a great challenge. Herein, bimetallic nanoparticles in a metal-organic framework (MOF), i.e., CuPd&at;ZIF-8 composite, featuring a cubic CuPd core and a porous ZIF-8 shell, have been rationally fabricated for this end. Given the unique physicochemical properties, the Cu nanocubes can not only convert solar energy into heat to accelerate the reaction but also serve as the seed for in situ formation of Pd nanoparticles (NPs) on their external surface to regulate the chemoselectivity of Pd active sites. The additional growth of the MOF shell is helpful to stabilize the CuPd core and offer regioselectivity via the steric hindrance effect. Ammonia borane provides active hydrogen species to significantly boost the hydrogenation and ensure the high selectivity. As a result, the CuPd&at;MOF exhibits high efficiency, featuring a turnover frequency (TOF, 6799 min-1) of 5-105 times higher than that in previous reports, and high chemo- and regioselectivity toward the semihydrogenation of alkynes, in the presence of NH3BH3 as a hydrogen source, under visible-light irradiation at ambient temperature.
- Guan, Qiaoqiao,Jiang, Hai-Long,Li, Luyan,Lu, Junling,Yang, Qihao,Yang, Weijie,Yu, Shu-Hong
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p. 7753 - 7762
(2020/08/21)
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- Method for Oligomerizing Olefins
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The present invention relates to a method for oligomerizing olefins, including the steps of: carrying out an oligomerization reaction of olefins by injecting an oligomerization transition metal catalyst, a cocatalyst, an olefin monomer and a solvent into a reactor; and injecting, into the reaction product of the oligomerization reaction, a catalyst inactivator including a gaseous inorganic material that contains oxygen.
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Paragraph 0115-0117
(2020/10/20)
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- ALCOHOL DEHYDRATION CATALYST, PREPARATION METHOD THE SAME AND METHOD FOR PREPARING ALPHA-OLEFINS USING THE SAME
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The present invention relates to a catalyst for dehydration of a primary alcohol, a method of preparing the same, and a method of producing an alpha-olefin using the same. The catalyst for dehydration of a primary alcohol according to the present invention has an excellent catalyst stability while having an excellent activity with respect to dehydration, and a high turnover frequency, such that a linear alpha-olefin with high purity may be produced with a high selectivity even in a case where a relatively small amount of a cocatalyst is added as compared with a homogeneous catalyst system.
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Paragraph 0126; 0127; 0130; 0131
(2020/11/24)
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- METHOD FOR PRODUCING ALIPHATIC LINEAR PRIMARY ALCOHOLS
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Provided are a method of preparing a linear primary alcohol, a catalyst for converting an α-olefin into an alcohol, and a method of converting an α-olefin into a linear primary alcohol, and the method of preparing a linear primary alcohol according to the present invention includes: charging a reactor with a heterogeneous catalyst including a cobalt oxide and a Cn olefin (S1); bringing the heterogeneous catalyst including a cobalt oxide into contact with the Cn olefin (S2); and supplying the reactor with a synthetic gas to obtain a Cn+1 alcohol (S3).
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Paragraph 0103; 0109
(2020/05/06)
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- NCP-Type Pincer Iridium Complexes Catalyzed Transfer-Dehydrogenation of Alkanes and Heterocycles?
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A series of NCP-type pincer iridium complexes, (RNCCP)IrHCl (2a—2c) and (BQ-NCOP)IrHCl 3, have been studied for catalytic transfer alkane dehydrogenation. Complex 3 containing a rigid benzoquinoline backbone exhibits high activity and robustness in dehydrogenation of alkanes to form alkenes. Even more importantly, this catalyst system was also highly effective in the dehydrogenation of a wide range of heterocycles to furnish heteroarenes.
- Wang, Yulei,Qian, Lu,Huang, Zhidao,Liu, Guixia,Huang, Zheng
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supporting information
p. 837 - 841
(2020/05/18)
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- Ethylene Tetramerisation: A Structure-Selectivity Correlation
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The effect of ethylene tetramerisation ligand structures on 1-octene selectivity is well studied. However, by-product formation is less understood. In this work, a range of PNP ligand structures are correlated with the full product selectivity and with catalyst activity. As steric bulk on the N-substituent increases, the product selectivity shifts from >10 % to 3% of both C6 cyclics and C16+ by-products. 1-Octene peaks at ca. 70%. Thereafter, only 1-hexene increases. Similar selectivity changes were observed for ortho-Ph-substituted PNP ligands. The C10-14 selectivity was less affected by the ligand structure. The ligand effect on the changes in selectivity is explained mechanistically. Lastly, an increase in ligand steric bulk was found to improve catalyst activity and reduce polymer formation by an order of magnitude. It is proposed that steric bulk promotes formation of cationic catalytic species which are responsible for selective ethylene oligomerisation.
- Makume, Boitumelo F.,Holzapfel, Cedric W.,Maumela, Munaka C.,Willemse, J. Alexander,van den Berg, Jan A.
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p. 2308 - 2315
(2020/11/03)
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- Method for Oligomerizing Ethylene
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The present invention relates to an oligomerization method of ethylene using a reactor equipped with a condenser, wherein the method comprises a step of pre-mixing a raw material composition at a low temperature, introducing the composition into the reactor, and inducing an ethylene oligomerization reaction at a low reaction pressure. According to the method of the present invention, it is possible to prepare an oligomer having excellent reaction activity and product selectivity, and even if the oligomerization reaction proceeds at a low pressure condition, energy consumption is reduced compared to a conventional heat removal method.COPYRIGHT KIPO 2020
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Paragraph 0054-0060
(2020/09/04)
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- Rh-catalyzed highly regioselective hydroformylation to linear aldehydes by employing porous organic polymer as a ligand
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In this work, we developed a new structural porous organic polymer containing biphosphoramidite unit, which can be used as a solid bidentate phosphorous ligand for rhodium-catalyzed solvent-free higher olefins hydroformylation. The resultant catalyst demonstrated unprecedently high regioselectivity to linear aldehydes and could be readily recovered for successive reuses with good stability in both catalytic activity and regioselectivity. This journal is
- Wang, Zhaozhan,Yang, Yong
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p. 29263 - 29267
(2020/10/06)
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- N,N,O-Coordinated tricarbonylrhenium precatalysts for the aerobic deoxydehydration of diols and polyols
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Rhenium complexes are well known catalysts for the deoxydehydration (DODH) of vicinal diols (glycols). In this work, we report on the DODH of diols and biomass-derived polyols using L4Re(CO)3as precatalyst (L4Re(CO)3= tricarbonylrhenium 2,4-di-tert-butyl-6-(((2-(dimethylamino)ethyl)(methyl)amino)methyl)phenolate). The DODH reaction was optimized using 2 mol% of L4Re(CO)3as precatalyst and 3-octanol as both reductant and solvent under aerobic conditions, generating the active high-valent rhenium speciesin situ. Both diol and biomass-based polyol substrates could be applied in this system to form the corresponding olefins with moderate to high yield. Typical features of this aerobic DODH system include a low tendency for the isomerization of aliphatic external olefin products to internal olefins, a high butadiene selectivity in the DODH of erythritol, the preferential formation of 2-vinylfuran from sugar substrates, and an overall low precatalyst loading. Several of these features indicate the formation of an active species that is different from the species formed in DODH by rhenium-trioxo catalysts. Overall, the bench-top stable and synthetically easily accessible, low-valent NNO-rhenium complex L4Re(CO)3represents an interesting alternative to high-valent rhenium catalysts in DODH chemistry.
- Klein Gebbink, Robertus J. M.,Li, Jing,Lutz, Martin
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p. 3782 - 3788
(2020/06/22)
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- Catalytic isomerization-hydroformylation of olefins by rhodium salicylaldimine pre-catalysts
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A series of new Schiff-base rhodium(i) water-soluble complexes (C1-C3), were prepared and characterized. These complexes served as catalyst precursors for the hydroformylation of 1-octene and resulted in excellent substrate conversions (>98%) with 100% chemoselectivities to aldehydes, under mild conditions. Notably, good regioselectivities towards branched aldehydes were observed clearly demonstrating the catalysts’ ability in thermodynamically favoured isomerization followed by hydroformylation (n/iso ratio ranging between 0.7-1.2). Interestingly, catalystC1uniquely promoted contra-thermodynamic isomerization of 2-octene to 1-octene with up to 50% conversion. The efficacy of catalystC1was further evaluated in the hydroformylation of longer chain olefins (C10-C12), methyl acrylate, ethyl acrylate and styrene. The catalyst displayed conversions >99% with the long chain substrates and much lower conversions with the acrylates. These water-soluble (pre)catalysts were recycled up to three times with no significant loss in catalytic activity and selectivity. Mercury poisoning tests were conducted and the experiments revealed that the conversion of the substrates into aldehydes was due to molecular active catalysts and not as a result of colloidal particles that could have formedin situthrough the decomposition of the catalyst precursor. Finally, the molecular catalyst responsible for activity was established using preliminary computational calculations.
- Sekoto, Pamela N.,Magengenene, Tseliso M.,Matsinha, Leah C.,Tia, Richard,Darkwa, James,Makhubela, Banothile C. E.
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p. 8751 - 8762
(2020/06/08)
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- Palladium-Catalyzed Oxidative Dehydrosilylation for Contra-Thermodynamic Olefin Isomerization
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We report a newly developed, palladium-catalyzed dehydrosilylation of terminal alkylsilanes that combines with chain-walking hydrosilylation to create a one-pot isomerization of internal olefins to terminal olefins. This catalytic dehydrosilylation is one of the few examples of thermal catalytic functionalizations of unactivated alkylsilanes. The reaction involves transmetalation of an alkylsilane, β-hydride elimination, release of the terminal olefin, and reoxidation of the palladium catalyst. A variety of linear internal olefins underwent the overall isomerization to terminal olefins in good yields and in good regioselectivities. Particularly noteworthy, isomerizations occurring over seven carbon units proceeded in yields that are comparable to those of isomerizations occurring over one carbon unit.
- Butcher, Trevor W.,Hanna, Steven,Hartwig, John F.,Wills, Tyler
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p. 8736 - 8741
(2020/09/23)
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- Carboxylate-Assisted β-(Z) Stereoselective Hydrosilylation of Terminal Alkynes Catalyzed by a Zwitterionic Bis-NHC Rhodium(III) Complex
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The zwitterionic compound [Cp*RhCl{(MeIm)2CHCOO}] is an efficient catalyst for the hydrosilylation of terminal alkynes with excellent regio- and stereoselectivity toward the less thermodynamically stable β-(Z)-vinylsilane isomer under mild reaction conditions. A broad range of linear 1-alkynes, cycloalkyl acetylenes, and aromatic alkynes undergo the hydrosilylation with HSiMe2Ph to afford the corresponding β-(Z)-vinylsilanes in quantitative yields in short reaction times. The reaction of aliphatic alkynes with HSiEt3 is slower, resulting in a slight decrease of selectivity toward the β-(Z)-vinylsilane product, which is still greater than 90%. However, a significant selectivity decrease is observed in the hydrosilylation of aromatic alkynes because of the β-(Z) → β-(E) vinylsilane isomerization. Moreover, the hydrosilylation of bulky alkynes, such as t-Bu-CCH or Et3SiCCH, is unselective. Experimental evidence suggests that the carboxylate function plays a key role in the reaction mechanism, which has been validated by means of density functional theory calculations, as well as by mass spectrometry and labeling studies. On the basis of previous results, we propose an ionic outer-sphere mechanism pathway in which the carboxylate fragment acts as a silyl carrier. Namely, the hydrosilylation mechanism entails the heterolytic activation of the hydrosilane assisted by the carboxylate function to give the hydrido intermediate [Cp*RhH{(MeIm)2CHCOO-SiR3}]+. The transference of the silylium moiety from the carboxylate to the alkyne results in the formation of a flat β-silyl carbocation intermediate that undergoes a hydride transfer from the Rh(III) center to generate the vinylsilane product. The outstanding β-(Z) selectivity results from the minimization of the steric interaction between the silyl moiety and the ligand system in the hydride transfer transition state.
- Puerta-Oteo, Raquel,Munarriz, Julen,Polo, Víctor,Jiménez, M. Victoria,Pérez-Torrente, Jesús J.
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p. 7367 - 7380
(2020/07/21)
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- Olefin reaction in the catalyst and the olefin production
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PROBLEM TO BE SOLVED: To provide a catalyst for obtaining an olefin in high selectivity with a vicinal diol as a raw material.SOLUTION: A catalyst for olefination reaction for use in a reaction to produce an olefin by a reaction of a polyol, having two adjacent carbon atoms each having a hydroxy group, with hydrogen comprises: a carrier; at least one oxide selected from the group consisting of oxides of the group 6 elements and oxides of the group 7 elements supported on the carrier; and at least one metal selected from the group consisting of silver, iridium, and gold supported on the carrier.SELECTED DRAWING: None
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Paragraph 0145-0146; 0149
(2020/10/31)
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- A Cp-based Molybdenum Catalyst for the Deoxydehydration of Biomass-derived Diols
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Dioxo-molybdenum complexes have been reported as catalysts for the deoxydehydration (DODH) of diols and polyols. Here, we report on the DODH of diols using [Cp*MoO2]2O as catalyst (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of [Cp*MoO2]2O, 1.1 equiv. of PPh3 as reductant, and anisole as solvent. Aliphatic vicinal diols are converted to the corresponding olefins by [Cp*MoO2]2O in up to 65 % yield (representing over 30 turnovers per catalyst) and 91 % olefin selectivity, which rivals the performance of other Mo-based DODH catalysts. Remarkably, cis-1,2-cyclohexanediol, which is known as quite a challenging substrate for DODH catalysis, is converted to 30 % of 1-cyclohexene under optimized reaction conditions. Overall, the mass balances (up to 79 %) and TONs per Mo achievable with [Cp*MoO2]2O are amongst the highest reported for molecular Mo-based DODH catalysts. A number of experiments aimed at providing insight in the reaction mechanism of [Cp*MoO2]2O have led to the proposal of a catalytic pathway in which the [Cp*MoO2]2O catalyst reacts with the diol substrate to form a putative nonsymmetric dimeric diolate species, which is reduced in the next step at only one of its Mo-centers before extrusion of the olefin product.
- Li, Jing,Lutz, Martin,Klein Gebbink, Robertus J. M.
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p. 6356 - 6365
(2020/11/30)
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- Method for catalytically oxidizing primary alcohol into corresponding carboxylic acid and simultaneously co-producing corresponding alpha olefin
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The invention relates to a method for catalytically oxidizing primary alcohol into corresponding carboxylic acid and simultaneously co-producing corresponding alpha olefin. The method comprises the following steps: mixing primary alcohol shown as a substrate (I), a catalyst cobalt salt, a nitrogen-containing ligand and a solvent, refluxing and stirring for 4-48 hours in an oxygen or air atmospherewith a certain pressure, and distilling and separating the reacted liquid to obtain carboxylic acid shown as (II) and alpha olefin in a certain proportion. The cobalt salt catalyst used in the methodis cheap and easy to obtain, the used nitrogen-containing ligand is a commercial nitrogen-containing compound, the used oxidant is oxygen or air, the reaction condition is mild, and various primary alcohols can be converted into corresponding carboxylic acids and alpha olefins at a high conversion rate under the condition of low cost.
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Paragraph 0030-0031
(2020/12/30)
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- Selective Semi-Hydrogenation of Terminal Alkynes Promoted by Bimetallic Cu-Pd Nanoparticles
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The selective semi-hydrogenation of terminal alkynes was efficiently performed, under mild reaction conditions (H 2 balloon, 110 °C), promoted by a bimetallic nanocatalyst composed of copper and palladium nanoparticles (5:1 weight ratio) supported on mesostructured silica (MCM-48). The Cu-PdNPS@MCM-48 catalyst, which demonstrated to be highly chemoselective towards the alkyne functionality, is readily prepared from commercial materials and can be recovered and reused after thermal treatment followed by reduction under H 2 atmosphere.
- Buxaderas, Eduardo,Volpe, María Alicia,Radivoy, Gabriel
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p. 1466 - 1472
(2019/03/07)
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- Dendrimer-Encapsulated Pd Nanoparticles, Immobilized in Silica Pores, as Catalysts for Selective Hydrogenation of Unsaturated Compounds
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Heterogeneous Pd-containing nanocatalysts, based on poly (propylene imine) dendrimers immobilized in silica pores and networks, obtained by co-hydrolysis in situ, have been synthesized and examined in the hydrogenation of various unsaturated compounds. The catalyst activity and selectivity were found to strongly depend on the carrier structure as well as on the substrate electron and geometric features. Thus, mesoporous catalyst, synthesized in presence of both polymeric template and tetraethoxysilane, revealed the maximum activity in the hydrogenation of various styrenes, including bulky and rigid stilbene and its isomers, reaching TOF values of about 230000 h?1. Other mesoporous catalyst, synthesized in the presence of polymeric template, but without addition of Si(OEt)4, provided the trans-cyclooctene formation with the selectivity of 90–95 %, appearing as similar to homogeneous dendrimer-based catalysts. Microporous catalyst, obtained only on the presence of Si(OEt)4, while dendrimer molecules acting as both anchored ligands and template, demonstrated the maximum activity in the hydrogenation of terminal linear alkynes and conjugated dienes, reaching TOF values up to 400000 h?1. Herein the total selectivity on alkene in the case of terminal alkynes and conjugated dienes reached 95–99 % even at hydrogen pressure of 30 atm. The catalysts synthesized can be easily isolated from reaction products and recycled without significant loss of activity.
- Karakanov, Edward A.,Zolotukhina, Anna V.,Ivanov, Andrey O.,Maximov, Anton L.
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p. 358 - 381
(2019/04/04)
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- Atomically Dispersed Ruthenium Species Inside Metal–Organic Frameworks: Combining the High Activity of Atomic Sites and the Molecular Sieving Effect of MOFs
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Incorporating atomically dispersed metal species into functionalized metal–organic frameworks (MOFs) can integrate their respective merits for catalysis. A cage-controlled encapsulation and reduction strategy is used to fabricate single Ru atoms and triatomic Ru3 clusters anchored on ZIF-8 (Ru1@ZIF-8, Ru3@ZIF-8). The highly efficient and selective catalysis for semi-hydrogenation of alkyne is observed. The excellent activity derives from high atom-efficiency of atomically dispersed Ru active sites and hydrogen enrichment by the ZIF-8 shell. Meanwhile, ZIF-8 shell serves as a novel molecular sieve for olefins to achieve absolute regioselectivity of catalyzing terminal alkynes but not internal alkynes. Moreover, the size-dependent performance between Ru3@ZIF-8 and Ru1@ZIF-8 is detected in experiment and understood by quantum-chemical calculations, demonstrating a new and promising approach to optimize catalysts by controlling the number of atoms.
- Ji, Shufang,Chen, Yuanjun,Zhao, Shu,Chen, Wenxing,Shi, Lijun,Wang, Yu,Dong, Juncai,Li, Zhi,Li, Fuwei,Chen, Chen,Peng, Qing,Li, Jun,Wang, Dingsheng,Li, Yadong
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supporting information
p. 4271 - 4275
(2019/03/07)
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- A General One-Pot Methodology for the Preparation of Mono- and Bimetallic Nanoparticles Supported on Carbon Nanotubes: Application in the Semi-hydrogenation of Alkynes and Acetylene
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A facile and straightforward methodology for the preparation of monometallic (copper and palladium) and bimetallic nanocatalysts (NiCu and PdCu) stabilized by a N-heterocyclic carbene ligand is reported. Both colloidal and supported nanoparticles (NPs) on carbon nanotubes (CNTs) were prepared in a one-pot synthesis with outstanding control on their size, morphology and composition. These catalysts were evaluated in the selective hydrogenation of alkynes and alkynols. PdCu/CNTs revealed an efficient catalytic system providing high selectivity in the hydrogenation of terminal and internal alkynes. Moreover, this catalyst was tested in the semi-hydrogenation of acetylene in industrially relevant acetylene/ethylene-rich model gas feeds and showed excellent stability even after 40 h of reaction.
- Lomelí-Rosales, Diego A.,Delgado, Jorge A.,Díaz de los Bernardos, Miriam,Pérez-Rodríguez, Sara,Gual, Aitor,Claver, Carmen,Godard, Cyril
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supporting information
p. 8321 - 8331
(2019/06/04)
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- Ultralow-content palladium dispersed in covalent organic framework for highly efficient and selective semihydrogenation of alkynes
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Developing noble-metal-based catalysts with ultralow loading to achieve excellent performance for selective hydrogenation of alkynes under mild reaction conditions is highly desirable but still faces huge challenges. To this end, a SO3H-anchored covalent organic framework (COF-SO3H) as the support was deliberately designed, and then ultralow-content Pd (0.38 wt %) was loaded by a wet-chemistry immersion dispersion method. The resulting Pd0.38/COF-SO3H composite exhibits outstanding performance for the selective hydrogenation of phenylacetylene with 97.06% conversion and 93.15% selectivity to styrene under mild reaction conditions (1 bar of H2, 25 °C). Noticeably, the turnover frequency value reaches as high as 3888 h-1, which outperforms most of reported catalysts for such use. Moreover, such a catalyst also exhibits excellent activity for a series of other alkynes and high stability without obvious loss of catalytic performance after five consecutive cycles.
- Li, Jian Hong,Yu, Zhi Wu,Gao, Zhi,Li, Jian Qiang,Tao, Yuan,Xiao, Yu Xin,Yin, Wen Hui,Fan, Ya Ling,Jiang, Chao,Sun, Li Jun,Luo, Feng
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supporting information
p. 10829 - 10836
(2019/08/22)
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- Pd-Catalyzed Synthesis of Vinyl Arenes from Aryl Halides and Acrylic Acid
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Acrylic acid is presented as an inexpensive, non-volatile vinylating agent in a palladium-catalyzed decarboxylative vinylation of aryl halides. The reaction proceeds through a Heck reaction of acrylic acid, immediately followed by protodecarboxylation of the cinnamic acid intermediate. The use of the carboxylate group as a deciduous directing group ensures high selectivity for monoarylated products. The vinylation process is generally applicable to diversely substituted substrates. Its utility is shown by the synthesis of drug-like molecules and the gram-scale preparation of key intermediates in drug synthesis.
- Gao, Yang,Ou, Yang,Goo?en, Lukas J.
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supporting information
p. 8709 - 8712
(2019/06/17)
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- Sodium diisopropylamide-mediated dehydrohalogenations: Influence of primary- A nd secondary-shell solvation
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Eliminations of alkyl halides by sodium diisopropylamide (NaDA) in tetrahydrofuran (THF)/hexane or THF/N,N-dimethylethylamine (DMEA) solutions are facile and complementary to analogous reactions of lithium diisopropylamide in THF. Rate studies show a dominance of monomer-based metalations and prevalent secondary-shell solvation effects overlaid on primary-shell effects. 1-Halooctanes exclusively undergo elimination rather than substitution. Rate and isotopic labeling studies on 1-bromooctane reveal an E2-like elimination pathway via trisolvated NaDA monomer. By contrast, 1-chlorooctane is eliminated via disolvated monomer through a carbenoid mechanism. exo-2-Norbornyl chloride and bromide are also eliminated via disolvated monomer; a syn E2 mechanism is inferred for these substrates. The cis- A nd trans-4-tert-butylcyclohexyl bromides show a preference for the elimination of the cis isomer (kcis/ax/ktrans/eq = 10). Rate and isotopic labeling studies are consistent with a trans-diaxial E2 elimination via trisolvated monomer for the cis isomer and a carbenoid mechanism via disolvated monomer for the trans isomer. Vicinal haloethers show substrate-dependent reactivities, affording alkynes and enol ethers. trans-1-Bromo-2-methoxycyclohexane provides enol ether 1-methoxycyclohexene, while trans-1-bromo-2-methoxycyclooctane provides dimeric products consistent with fleeting cycloocta-1,2-diene (cyclic allene), which was fully characterized as two conformers.
- Ma, Yun,Algera, Russell F.,Woltornist, Ryan A.,Collum, David B.
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supporting information
p. 10860 - 10869
(2019/09/30)
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- Hydrogenation of hydrophobic substrates catalyzed by gold nanoparticles embedded in Tetronic/cyclodextrin-based hydrogels
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Hydrogenation of alkenes, alkynes and aldehydes was investigated under biphasic conditions using Au nanoparticles (AuNP) embedded into combinations of α-cyclodextrin (α-CD) and a poloxamine (Tetronic90R4). Thermo-responsive AuNP-containing α-CD/Tetronic90R4 hydrogels are formed under well-defined conditions of concentration. The AuNP displayed an average size of ca. 7 nm and a narrow distribution, as determined by TEM. The AuNP/α-CD/Tetronic90R4 system proved to be stable over time. Upon heating above the gel-to-sol transition temperature, the studied catalytic system allowed hydrogenation of a wide range of substrates such as alkenes, alkynes and aldehydes under biphasic conditions. Upon repeated heating/cooling cycles, the Au NP/α-CD/Tetronic90R4 catalytic system could be recycled several times without a significant decline in catalytic activity.
- Chevry,Menuel,Léger,No?l,Monflier,Hapiot
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p. 9865 - 9872
(2019/07/04)
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- Perfluorohydrocarbyl-N2-phosphinyl amidine compounds, chromium salt complexes, catalyst systems, and their use to oligomerize ethylene
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A catalyst system comprising an N2-phosphinylamidine chromium salt complex having Structure PFHNPACr I: wherein Rf1, Rf2, Rf4, and Rf5 are independently selected from a perfluorohydrocarbyl group; and CrXp is a chromium salt; X is a monoanion, and p is an integer from 2 to 6. A process comprising a) contacting i) ethylene, ii) a catalyst system comprising an N2-phosphinylamidine chromium salt complex having Structure PFHNPACr I: wherein each Rf1, Rf2, Rf4, and Rf5 are independently selected from a perfluorohydrocarbyl group and CrXp is a chromium salt; X is a monoanion and p is an integer from 2 to 6, and iii) optionally an organic reaction medium; and b) forming an oligomer product in a reaction zone.
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Page/Page column 40-44
(2019/02/07)
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- Chromium complexes based on thiophene–imine ligands for ethylene oligomerization
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A new set of Cr(III) complexes, {L}CrCl3(THF), based on thiophene–imine (2a, L?=?PhOC6H4(N═CH)-2-SC4H3; 2b, L?=?PhOC2H4(N═CH)-2-SC4H3; 2c, L?=?Ph(NH)C2H4(N═CH)-2-SC4H3; 2d, L?=?PhOC6H4(N═CH)-2-SC4H2-5-Ph; 2e, L?=?Ph(NH)C2H4(N═CH)-2-SC4H2-5-Ph) have been prepared and characterized using elemental analysis and infrared spectroscopy. Upon activation with methylaluminoxane, all the chromium complexes generated active systems affording a nonselective distribution of α-olefins with turnover frequencies in the range 9500–93?500?(mol ethylene)?(mol Cr)?1?h?1, and producing mostly oligomers (95.0–99.3?wt% of total products). Small amounts of polymer were produced in these oligomerization reactions (0.8–8.2?wt%). The catalytic activities were quite sensitive to the ligand environment. Moreover, the effects of oligomerization parameters (temperature, [Al]/[Cr] molar ratio, time) on the activity and on the product distribution were examined.
- Ferreira, Jorge,Zilz, Raquel,Boeira, Igor S.,da Silva, Sabrina M.,Casagrande, Adriana C.A.,Casagrande, Osvaldo L.
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- α-Diphenylphosphino-N-(pyrazin-2-yl)glycine as a ligand in Ni-catalyzed ethylene oligomerization
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α-Diphenylphosphino-N-(pyrazin-2-yl)glycine was synthesized by the three-component condensation of diphenylphosphine, glyoxylic acid hydrate, and 2-aminopyrazine and its structure was confirmed by X-ray diffraction. It reacted with [Ni(COD)2] (COD is cycloocta-1,5-diene) to give complexes that were tested as catalysts for selective dimerization/oligomerization of ethylene to but-1-ene (main product) and C6–C14 α-olefins, respectively.
- Soficheva, Olga S.,Bekmukhamedov, Giyjaz E.,Dobrynin, Alexey B.,Heinicke, Joachim W.,Sinyashin, Oleg G.,Yakhvarov, Dmitry G.
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p. 575 - 577
(2019/11/02)
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- Catalyst Systems and Ethylene Oligomerization Method
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Disclosed herein is a catalyst system comprising (i) a heterocyclic 2-[(phosphinyl)aminyl]imine transition metal compound complex having Structure I wherein T is oxygen or sulfur, R1 and R2 are each independently a C1 to C20 organyl group consisting essentially of inert functional groups, R3 is hydrogen or a C1 to C20 organyl group, L is a C1 to C20 organylene group consisting essentially of inert functional groups, MXp represents a transition metal compound where M is a transition metal, X is a monoanion, and p is an integer from 1 to 6, Q is a neutral ligand, and q ranges from 0 to 6, and (ii) an organoaluminum compound. Also disclosed herein is a process comprising contacting (i) ethylene, (ii) a catalyst system comprising (a) a heterocyclic transition metal compound complex having Structure I as described herein and (b) an organoaluminum compound, and (iii) optionally hydrogen to form an oligomer product.
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Paragraph 0170-0172
(2019/06/14)
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- 1,5-Naphthyl-linked bis(imino)pyridines as binucleating scaffolds for dicobalt ethylene oligo-/polymerization catalysts: Exploring temperature and steric effects
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Six examples of dinuclear bis(imino)pyridine-cobalt(ii) complexes, [1,5-{2-(CMeN)-6-(CMeN(2,6-R12-4-R2-C6H2))C5H3N}2(C10H6)]Co2Cl4 (R1 = Me, R2 = H Co1; R1 = Et, R2 = H Co2; R1 = iPr, R2 = H Co3; R1 = Me, R2 = Me Co4; R1 = Et, R2 = Me Co5; R1 = CHPh2, R2 = Me Co6), have been prepared from the corresponding bis(tridentate) compartmental ligands (L1-L6) in reasonable yields. The molecular structures of Co3 and Co5 revealed two N,N,N-cobalt dichloride units to adopt anti-positions about the 1,5-naphthyl linking unit, with each cobalt center exhibiting a distorted trigonal bipyramidal geometry. On activation with either MAO or MMAO, Co1-Co6 were shown to promote both polymerization and oligomerization of ethylene with high overall activities (up to 1.03 × 107 gPE per·mol(Co) per·h for Co1/MAO at 70 °C). Curiously, on increasing the reaction temperature a larger proportion of polymer was noted, while at lower temperature an enhanced selectivity for oligomer was seen. In general, the oligomeric products displayed Schulz-Flory distributions with high selectivities for α-olefins (>99%). On the other hand, the highly linear polymers displayed narrow dispersities and comprised both fully saturated and unsaturated chain ends with the vinyl content (-CHCH2) found to rise with the reaction temperature. By modulating the steric hindrance exerted by the ortho-R1 substituents in the precatalyst, polyethylenes displaying a remarkably broad range of molecular weights could be obtained [from 4.52 kg mol-1 (R1 = Me) to 246.7 kg mol-1 (R1 = CHPh2)].
- Chen, Qiang,Suo, Hongyi,Zhang, Wenjuan,Zhang, Randi,Solan, Gregory A.,Liang, Tongling,Sun, Wen-Hua
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supporting information
p. 8264 - 8278
(2019/06/18)
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