- Tailored catalytic propene trimerization over acidic zeolites with tubular pores
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(Graph Presented) Slim through spatial constraints: A higher content of linear and monobranched propene trimers is obtained with ZSM-22 as catalyst than with many other zeolite catalysts (see picture). This is explained by the constraints imposed by the diameter of the tubular pores of ZSM-22. ZSM-22 also brings an important environmental benefit compared with the presently used industrial catalyst silica-supported phosphoric acid.
- Martens, Johan A.,Verrelst, Wim H.,Mathys, Georges M.,Brown, Stephen H.,Jacobs, Pierre A.
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Read Online
- Selecting double bond positions with a single cation-responsive iridium olefin isomerization catalyst
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The catalytic transposition of double bonds holds promise as an ideal route to alkenes of value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, normally requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst selectively produces either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on noncovalent modifications.
- Camp, Andrew M.,Kita, Matthew R.,Blackburn, P. Thomas,Dodge, Henry M.,Chen, Chun-Hsing,Miller, Alexander J.M.
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supporting information
p. 2792 - 2800
(2021/03/01)
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- Catalytic Hydrogenation of Alkenes and Alkynes by a Cobalt Pincer Complex: Evidence of Roles for Both Co(I) and Co(II)
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The Co(I) complex, [Co(N2)(CyPNP)] (CyPNP = anion of 2,5-bis-(dicyclohexylphosphinomethyl)pyrrole), is active toward the catalytic hydrogenation of terminal alkenes and the semi-hydrogenation of internal alkynes under 2 bar of H2 (g) at room temperature. The products of alkyne semi-hydrogenation are a mixture of E- and Z-alkenes. By contrast, use of the related cobalt(I) precatalyst, [Co(PMe3)(CyPNP)], results in formation of exclusively Z-alkenes. A semi-stable Co(II) species, [CoH(CyPNP)], can also be generated by treatment of degassed solutions of [Co(N2)(CyPNP)] with H2. The CoII-hydride displays activity toward both alkene hydrogenation and isomerization, but its instability hampers implementation as a catalyst. Several species relevant to potential catalytic intermediates have been isolated and detected in solution. These compounds include alkene and alkyne adducts of Co(I) as well as a Co(III) dihydride species. Catalytic results with the compounds examined are most consistent with a process involving shuttling between Co(I) and Co(III) states. However, generation of small quantities of Co(II) during catalytic turnover appears to be responsible for the isomerization observed for alkyne semi-hydrogenation. The interplay of cobalt oxidation states within the same catalyst system is discussed in the context of mechanistic scenarios for catalytic hydrogenation.
- Alawisi, Hussah,Arman, Hadi D.,Tonzetich, Zachary J.
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p. 1062 - 1070
(2021/04/09)
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- METAL ORGANIC FRAMEWORKS, THEIR SYNTHESIS AND USE
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A novel metal organic framework, EMM-33, is described having the structure of UiO-67 and comprising bisphosphonate linking ligands. EMM-33 has acid activity and is useful as a catalyst in olefin isomerization. Also disclosed is a process of making metal organic frameworks, such as EMM-33, by heterogeneous ligand exchange, in which linking ligands having a first bonding functionality in a host metal organic framework are exchanged with linking ligands having a second different bonding functionality in the framework.
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Page/Page column 15
(2018/11/26)
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- An Agostic Iridium Pincer Complex as a Highly Efficient and Selective Catalyst for Monoisomerization of 1-Alkenes to trans-2-Alkenes
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A unique Ir complex (tBuNCCP)Ir with the pyridine–phosphine pincer as the sole ligand, featuring a dual agostic interaction between the Ir and two σ C?H bonds from a tBu substituent, has been prepared. This complex exhibits exceptionally high activity and excellent regio- and stereoselectivity for monoisomerization of 1-alkenes to trans-2-alkenes with wide functional-group tolerance. Reactions can be performed in neat reactant on a more than 100 gram scale using 0.005 mol % catalyst loadings with turnover numbers up to 19000.
- Wang, Yulei,Qin, Chuan,Jia, Xiangqing,Leng, Xuebing,Huang, Zheng
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supporting information
p. 1614 - 1618
(2017/02/05)
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- Nonredox Metal-Ion-Accelerated Olefin Isomerization by Palladium(II) Catalysts: Density Functional Theory (DFT) Calculations Supporting the Experimental Data
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Redox metal-ion-catalyzed olefin isomerization represents one of the important chemical processes. This work illustrates that nonredox metal ions can sharply accelerate Pd(II)-catalyzed olefin isomerization, while Pd(II) alone is very sluggish. Nuclear magnetic resonance (NMR) and ultraviolet-visible light (UV-vis) characterizations disclosed that the acceleration effect originates from the formation of heterobimetallic Pd(II) species with added nonredox metal ions, which improves the C-H activation capability of the Pd(II) moiety. Density functional theory (DFT) calculations further confirmed the sharp decrease of the energy barrier in C-H activation by the heterobimetallic Pd(II)/Al(III) species.
- Senan, Ahmed M.,Qin, Shuhao,Zhang, Sicheng,Lou, Chenling,Chen, Zhuqi,Liao, Rong-Zhen,Yin, Guochuan
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p. 4144 - 4148
(2016/07/12)
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- CATALYST AND PROCESS FOR THE CO-DIMERIZATION OF ETHYLENE AND PROPYLENE
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Disclosed are novel catalyst solutions comprising an organic complex of nickel, an alkyl aluminum compound, a solvent, and a phosphine compound, that are useful for the preparation of butenes, pentenes and hexenes by the co-dimerization or cross-dimerization of ethylene and propylene. Also disclosed are processes for the dimerization of ethylene and propylene that utilize these catalyst solutions. The catalyst systems described herein demonstrate that, depending on the choice of phosphine compound used with the catalytically active nickel, it is indeed possible to lower the concentration of hexene olefins relative to butenes and pentenes, even in the presence of excess propylene. The selectivity to the linear or branched pentene product can also be controlled by the selection of the phosphine compound. The catalyst solutions may be used with mixtures of olefins.
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Paragraph 0082
(2015/03/28)
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- Alkene isomerisation catalysed by a ruthenium PNN pincer complex
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The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. The catalyst tested positive! A dearomatised ruthenium PNN (2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) pincer complex, [Ru(CO)H(PNN)], was evaluated as an alkene isomerisation catalyst. The isomerisation reaction was greatly accelerated by the addition of alcohols, in particular isopropanol. Isomerisation of terminal to internal alkenes took place at room temperature. A mechanism was proposed based on variable-temperature NMR spectroscopy.
- Perdriau, Sébastien,Chang, Mu-Chieh,Otten, Edwin,Heeres, Hero J.,De Vries, Johannes G.
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supporting information
p. 15434 - 15442
(2016/02/18)
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- Magnetic core-shell nanoparticles as carriers for olefin dimerization catalysts
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We report the covalent support of functionalized nickel complexes on magnetic core-shell hybrid particles γ-Fe2O3/ SiO2. Two completely different ways of connecting the particle with these nickel complexes were carried out. The first approach used the hydrosilylation method between the alkene-substituted nickel complex and a silane. In a second approach, the particles were connected with the complexes by means of click chemistry (copper-catalyzed Huisgen 1,3-dipolar cycloaddition). For this purpose, the nickel complexes were substituted with an alkyne moiety. Transmission and scanning electron microscopies, energy-dispersive X-ray diffraction, and FTIR spectroscopy were the methods employed to characterize the successful heterogenization of the nickel complexes. Copyright
- Ruhland, Thomas M.,Lang, Julian R.V.,Alt, Helmut G.,Mueller, Axel H.E.
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p. 2146 - 2153
(2013/06/26)
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- Stereoselective alkene isomerization over one position
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Although controlling both the position of the double bond and E:Z selectivity in alkene isomerization is difficult, 1 is a very efficient catalyst for selective mono-isomerization of a variety of multifunctional alkenes to afford >99.5% E-products. Many reactions are complete within 10 min at room temperature. Even sensitive enols and enamides susceptible to further reaction can be generated. Catalyst loadings in the 0.01-0.1 mol% range can be employed. E-to-Z isomerization of the product from diallyl ether was only -6 times as fast as its formation, showing the extremely high kinetic selectivity of 1.
- Larsen, Casey R.,Grotjahn, Douglas B.
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supporting information; experimental part
p. 10357 - 10360
(2012/08/08)
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- Homogeneous Dimerization Catalysts Based on Vanadium
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A series of new bis(imino)pyridine vanadium(III) complexes was synthesized according to formula: They were tested for the homogeneous catalytic dimerization of propylene after activation with MAO and showed excellent selectivity for dimerization. The catalysts can be used with or without PPh3 as an additive to produce ≧80% dimerized alkenes.
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Page/Page column 4; 6
(2011/04/18)
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- Homogeneous catalytic dimerization of propylene with bis(imino)pyridine vanadium(III) complexes
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A series of new bis(imino)pyridine vanadium(III) complexes was synthesized. They were tested for the homogeneous catalytic dimerization of propylene after activation with MAO. The activity and selectivity depend on the ligand structure of the corresponding organic coordination compound. The influence of PPh3 as an additive was investigated and high dependency could be observed.
- Lang, Julian R.V.,Denner, Christine E.,Alt, Helmut G.
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experimental part
p. 45 - 49
(2010/07/08)
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- Insight into cis-to-trans olefin isomerisation catalysed by group 4 and 6 cyclopentadienyl compounds
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Intramolecular isomerisation of the pendant allyl unit present in the model compound [MoH(eta;5-C5H4SiMe 2CH2CH=CH2)- (CO)3] reported before was investigated by DFT calculations.
- Chahboun, Ghaita,Petrisor, Cristina E.,Gomez-Bengoa, Enrique,Royo, Eva,Cuenca, Tomas
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experimental part
p. 1514 - 1520
(2009/07/10)
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- High yield of liquid range olefins obtained by converting i-propanol over zeolite H-ZSM-5
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Methanol, ethanol, and i-propanol were converted under methanol-to-gasoline (MTH)-like conditions (400°C, 1-20 bar) over zeolite H-ZSM-5. For methanol and ethanol, the catalyst lifetimes and conversion capacities are comparable, but when i-propanol is use
- Mentzel, Uffe V.,Shunmugavel, Saravanamurugan,Hruby, Sarah L.,Christensen, Claus H.,Holm, Martin S.
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experimental part
p. 17009 - 17013
(2010/03/23)
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- Kinetics of the thermal isomerization of 1,1,2-trimethylcyclopropane
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The Arrhenius parameters for the gas phase, unimolecular structural isomerizations of 1,1,2-trimethylcyclopropane to three isomeric methylpentenes and two dimethyl-butenes have been determined over a wide range of temperatures, 688-1124 K, using both static and shock tube reactors. For the overall loss of reactant. Ea =63.7 (±0.5) kcal/mol and log10 A= 15.28 (±0.12). These values are higher by 2.6 kcal/mol and 0.7-0.8 than previously reported from experimental work or predicted from thermochemical calculations. Ea for the formation of trans-4-methyl-2-pentene is 1.5 kcal/mol higher than Ea for the formation of the cis isomer, which is identical to the Ea difference previously reported for the formation of trans- and cis-2-butene from methylcyclopropane. Substitution of methyl groups for hydrogen atoms on the cyclopropane ring is expected to weaken the C - C ring bonds, and it has been reported previously that activation energies for structural isomerizations of methylcyclo-propanes do decrease substantially over the series cyclopropane > methylcyclopropane > 1, 1-or 1,2-dimethylcyclopropane. However, the present study shows that the trend does not continue beyond dimethylcyclopropane isomerization. Besides reductions in C - C bond energy, steric interactions may be increasingly important in determining the energy surface and conformational restrictions near the transition state in isomerizations of the more highly substituted methylcyclopropanes.
- Lewis, David K.,Hughes, Steven V.,Miller, Justine D.,Schlier, Jessica,Wilkinson, Kevin A.,Wilkinson, Sara R.,Kalra, Bansi L.
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p. 475 - 482
(2008/02/09)
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- Propylene bulk phase oligomerization with bisiminepyridine iron complexes in a calorimeter: Mechanistic investigation of 1,2 versus 2,1 propylene insertion
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Iron(II) complexes were synthesized with bisiminepyridine ligands of low steric demand. Activation with modified-methylaluminoxane (25 mol.% isobutyl groups) generated very active catalysts for propylene oligomerization. The oligomerizations were carried out in liquid propylene in a heat flow calorimeter. The oligomers were separated by preparative gas chromatography and the dimers and trimers analyzed using analytical gas chromatography, 1 H-NMR- and 13C-NMR-spectroscopy. With knowledge of the dimer and trimer structure, we were able to establish a mechanistic pathway for propylene insertion and obtained knowledge about the iron alkyl species involved. Analysis of the various dimers formed allowed us to determine the percentage of 1,2 versus 2,1 propylene insertions. Considering the same iron alkyl species with ligands of different steric demand, a change in the probabilities for 1,2 versus 2,1 propylene insertions can be observed. With this knowledge, the catalyst behavior for ligands of varying steric demand can be predicted.
- Babik, Sebastian Thomas,Fink, Gerhard
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p. 209 - 219
(2007/10/03)
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- A Dynamic Equilibrium of Oxaphosphetanes
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The course of the Wittig reaction was investigated by rapid injection NMR spectroscopy.Rate constants for the formation of oxaphosphetanes were determined.A new dynamic equilibrium of oxaphosphetanes was observed for the first time.The solvent and substituent dependence of the new effect was investigated.By labeling various oxaphosphetanes with 13C and 17O the lithium salt dependence of the new equilibrium was shown.A lithium adduct of oxaphosphetanes under these conditions is proposed. - Key Words: Wittig reaction / Rapid injection NMR / Dynamic NMR / Oxaphosphetanes
- Geletneky, Christian,Foersterling, Frank-Holger,Bock, Willi,Berger, Stefan
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p. 2397 - 2402
(2007/10/02)
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- Acid-Base Properties of Modified Aluminas
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The acid-base properties of modified aluminas (SO42-, PO43-, Cl-, F-, Mg2+ and Na+, 0.2-2.0 wt.percent) have been investigated by FTIR spectroscopy of probe molecules (pyridine and CDCl3), CO2 TPD and the dehydration of 4-methyl-pentan-2-ol.The results of these methods and those of previous NH3 TPD studies were compared in order to establish a classification of our aluminas.There is very good agreement between the results of the five methods.The various modifying ions have effects as summarised in the following acidity-basicity scale: Na+ 2+ 3- - 2- , - increasing basicity).Fluorine is distinguished from the other ions as it is able to create Broested-acidic sites.CO2 TPD is an adequate method for basicity measurement.NH3 and CO2 TPD give complementary results.Furthermore, FTIR spectroscopy of adsorbed CDCl3 gives valuable information on the effects of ions on the basic strengths.
- Berteau, Pascal,Kellens, Marie-Ange,Delmon, Bernard
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p. 1425 - 1431
(2007/10/02)
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- METAL COMPLEXES IN CATALYTIC CONVERSION OF OLEFINS. 3. CATALYTIC DIMERIZATION OF ETHYLENE AND PROPYLENE BY Ni(PPh3)n-Et3Al2Cl3 SYSTEM
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The Ni(PPh3)n-Et3Al2Cl3 catalytic system was found to be most effective for the dimerization of ethylene and propylene when the ligands Bu3PO and (BuO)2-PNEt2 were used in the Ni complex.For propylene dimerization in the liquid phase, the yield was 54 kmole/mole Nih at 40 - 55 deg C.Using mathematical planing methods for the experiments the optimum conditions range for the formation of hexanes was found, in which selectivity for dimerization reached 85-96percent at 80-90percent conversion.
- Furman, D. B.,Kudryashev, A. V.,Ivanov, A. O.,Pogorelov, A. G.,Yanchevskaya, T. V.,Bragin, O. V.
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p. 444 - 447
(2007/10/02)
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- Regioselective Hydrogenation of Conjugated Dienes Catalyzed by Hydridopentacyanocobaltate Anion using β-Cyclodextrin as the Phase-Transfer Agent and Lanthanide Halides as Promotors
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β-Cyclodextrin is a useful phase-transfer agent for the hydrogenation of conjugated dienes to monoolefins catalyzed by the in situ generated hydridopentacyanocobaltate anion.This reaction, which usually proceeds by 1,2-addition to the diene, is promoted by cerium or lanthanum chloride.Polyethyleneglycol (PEG-400), with or without added lanthanide, can also used as the phase-transfer agent for the reduction process.
- Lee, Jong-Tae,Alper, Howard
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p. 1854 - 1856
(2007/10/02)
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- Organometallische Komplexverbindungen IX. Steuerung der optischen Induktion
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Bis(μ-methyl-1,3-dimethyl-η3-allyl-nickel) which has been modified with chiral P ligands react with carbon monoxide to give the optically active 3-methyl-E-4-hexene-2-one.Low-temperature studies (DSC, 13C NMR) have indicated that this reaction is too fast to observe any intermediates.A suitable phosphine was chosen so that the chiral substituent is kept constant (1R,3R,4S-(-)-menthyl) and the other two are of the same, mostly achiral type (either P(-)MenthX2 or P(O(-)Menth)X2), the extent and direction of optical induction depends strongly on the concentration and the type of P ligand examined.Furthermore, changes in achiral parts of the P ligand after special order factors can lead to conversion into the excess enantiomer.Up to now the usual strategy to obtain the optical antipode has been to change the chirality of the educt.Therefore both enantiomers may be necessary.In our case only chiral precursor is needed and for this reason there is less need to draw from the natural pool, which should be useful for asymmetric synthesis.
- Bartik, T.,Gerdes, I.,Heimbach, P.,Schulte, H.-G.
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p. 359 - 370
(2007/10/02)
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- Process for preparing internal olefins
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A process for isomerizing an olefin to an internal olefin in the presence of a solid base which is obtainable by heating an alkali metal hydride and alumina, wherein the alumina has been pretreated with at least one salt selected from the group consisting of alkali metal carbonates and alkali metal aluminates, in an atmosphere of an inert gas at a temperature of 200 to 450° C.
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- Solid base, process for preparing the same and use of the same in preparation of internal olefins
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A solid base which is obtainable by reacting alumina with an alkali metal hydroxide and an alkali metal hydride or reacting water-containing alumina with an alkali metal hydride in an amount more than the molar equivalent of water container in the water-containing alumina, at a temperature of 200° to 500° C. in an inert gas atmosphere can effectively catalyze various reactions, particularly isomerization of olefins.
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- Komplexkatalyse XXIX. Kationische Allylbis(ligand)nickel(II)hexafluorophosphate PF6 und die Kombination /Et2AlCl als Katalysatoren fuer die Propendimerisation
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The cationic allylbis(ligand)nickel(II) complexes PF6 with L=P(OPh)3, P(OThym)3 and SbPh3 were found to be efficient catalysts for the oligomerization of propene under a l0 bar pressure of the monomer.The main products are dimers, and specifically the methylpentenes.The /Et2AlCl system catalyzes propene dimerization at atmospheric pressure with high activity, and selectivity similar to that of the cationic allylbis(ligand)nickel(II) complexes.In a kinetic analysis the rate law and the activation parameters ΔH and ΔS were determined for the propene dimerization with this catalytic system.
- Balbolov, Entscho,Mitkova, Magdalena,Kurtev, Kurty,Gehrke, Joerg-Peter,Taube, Rudolf
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p. 247 - 256
(2007/10/02)
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- Reactivity and Intersystem Crossing of Singlet Methylene in Solution
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Evidence is reported wich demonstrates that singlet methylene, produced from the photolysis of diazomethane or diazirine undergoes intersystem crossing to form triplet methylene in perfluorohexane solvent.The results of triplet sensitized photolysis and of direct photolysis experiments with dilute concentrations of substrate (cis- and trans-2-pentene and chloroform) appear to be essentially identical.Stern-Volmer analyses of the competition kinetics between acetonitrile and 2-pentenes or chloroform for singlet methylene are consistent with the near diffusion controlled reactivity of singlet methylene.With the assumption of diffusion-controlled reactions for singlet methylene, plots of the quantum yield for singlet vs. triplet reaction for methylene allow the first estimate (-1) of the rate of intersystem crossing of singlet methylene in the condensed phase.This value is considerably smaller than the value that is extrapolated to the solution phase from results in the gas phase.The possible reasons for this difference are discussed.
- Turro, Nicholas J.,Cha, Yuan,Gould, Ian R.
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p. 2101 - 2107
(2007/10/02)
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- Enthalpies of hydrogenation of the hexenes
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The enthalpies of hydrogenation are given for all isomers of hexene.The enthalpy of isomerization of 2,3-dimethylbut-1-ene to 2,3-dimethylbut-2-ene is discussed in relation to the enthalpies of endocyclic isomerization of methylenecyclopentane and methylenecyclohexane to the corresponding methylcycloalk-1-enes, which have also been determined by hydrogen thermochemistry.
- Rogers, D. W.,Crooks, Evon,Dejroongruang, Kosol
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p. 1209 - 1216
(2007/10/02)
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- Thermal and photochemical olefin isomerizations with complex as initiator
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Irradiation of the complex in an olefin as a solvent promotes stereospecific photoassisted isomerizations: olefins with terminal double bonds are rapidly isomerized into 2-alkenes with an E-configuration.Kinetic studies of hydrogen migrations and of Z-E isomerizations of disubstituted olefins have demonstrated the influence of substitution and of branching of the hydrocarbon chain on the course of the reaction.Formation of paramagnetic complexes of TiIII that are probably intermediates in these reactions has been confirmed by ESR.The same reactions, but with a lower stereoselectivity, are initiated thermally by the complex.
- Courtot, P.,Pichon, R.,Raoult, Y.,Salauen, J. Y.
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- DIMERISATION DE MONOOLEFINES CATALYSEE PAR DES COMPLEXES DU NICKEL ET DU COBALT GENERES ELECTROCHIMIQUEMENT
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Dimerization of olefins was performed with NiL2X2 and CoL2X2 complexes by an electrochemical reduction process under controlled cathodic potential.The influence of several parameters (choice of anode, supporting electrolyte, ligand, temperature and pressure) was studied in order to increase the dimer production and selectivity.In case of ethylene, with nickel-based catalysts, 2-butenes are formed selectively with a turn-over number of 12 000 within 50 h.With propylene as substrate methylpentenes are the main products, in which case the reaction rate appears to be two orders of magnitude lower than with ethylene under identical conditions.Although less active, cobalt based catalysts show an unusual behaviour, as they are particularly selective for 1-butene production (>90percent).
- Masotti, H.,Wallet, J. C.,Pfeiffer, G.
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p. 241 - 252
(2007/10/02)
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- METATHESIS AND OLIGOMERIZATION OF PROPENE OVER MOLYBDENA-ALUMINA CATALYSTS
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Metathesis of propene at 313 K and its oligomerization at 470-550 K were studied over a molybdena-alumina catalyst pretreated under various conditions.Activity of the catalyst decreased in both reactions as a result of elution with nitrogen at high temperature (823 K) after reduction with hydrogen.Ammonia was found to be an effective poison in both reactions.Hydrogen adsorbed at high temperature on reduced catalyst poisoned metathesis but did not influence oligomerization.Conversion in oligomerization of propene and selectivity in formation of C6 alkenes varied in an identical way under various conditions.
- Engelhardt, Jozsef,Kallo, Denes
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p. 249 - 264
(2007/10/02)
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- SELECTIVE HYDROGENATION OF CONJUGATED DIENES CATALYZED BY THIOCYANATOTRIS(TRIPHENYLPHOSPHINE)COBALT(I).
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Thiocyanatotris(triphenylphosphine)cobalt(I) prepared in situ from bis(thiocyanato)bis(triphenylphosphine)cobalt(II), triphenylphosphine, zinc bromide, selectively hydrogenated conjugated dienes to the corresponding cis-monomenes. The C//2-or/ and C//3-methyl substituted 1,3-butadienes enhance the reactivity by a factor of 2. 3 per one methyl group, while C//1- or/and C//4-methyl substituted 1,3-butadienes lower the reactivity by a factor of 1/23 per one methyl group. In the hydrogenation of cyclic conjugated dienes alpha -angle is closely related to the hydrogenation rate. The rates of hydrogenation in cyclic ethers are greater than those in acyclic ethers, but the cis-selectivity in acyclic ethers is much higher.
- Nakayama,Kanai
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- Equilibration of 5-Methyl-3-hexen-2-one and 5-Methyl-3-hexen-2-one and of XCH2CH=CYZ/XCH=CHCHYZ Pairs in General
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The equilibrium constant for isomerization of 5-methyl-4-hexen-2-one to trans-5-methyl-3-hexen-2-one in tert-butyl alcohol at 25 deg C has been found to be 0.40, which is smaller by 250-fold than a literature value.This and other equilibrium constants for reactions of the type XCH2CH=CMe2 XCH=CHCHME2 are shown to be consistent with the double bond stabilizing abilities of various groups as measured by equilibrium constants for reactions of the type XCH2CH=CHY XCH=CHCH2Y.The general case of isomerizations of the type XCH2CH=CYZ XCH=CHCHYZ is also discussed.
- Hine, Jack,Linden, Shwn-Meei
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p. 584 - 587
(2007/10/02)
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- ETUDE DE L'ISOMERISATION DU METHYL-4 PENTENE-1 PAR L'HYDRIDO DIAZOTE TRIS(TRIPHENYLPHOSPHINE)COBALT(I): CoHN2(PPh3)3
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At 25 deg C, and under 1 to 7 bar nitrogen pressure, the isomerization of 4-methyl-1-pentene catalyzed in benzene by CoHN2(PPh3)3 involves two active species: HCoN2(S1)(PPh3)2 and HCo(S1)(PPh3)3, respectively, in greater quantities at higher (P(N2) > 7 bars) and small quantities at P(N2) - O nitrogen pressures. The kinetic study shows that the rate of the reaction is always ruled by the equation:
- Petit, F.,Arzouyan, C.,Peiffer, G.,Gaydou, E.
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p. 261 - 272
(2007/10/02)
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