- NNNO-Heteroscorpionate nickel (II) and cobalt (II) complexes for ethylene oligomerization: the unprecedented formation of odd carbon number olefins
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The unprecedented observation of odd carbon number olefins is reported during nickel- catalyzed ethylene oligomerization. Two complexes based on Co (II) and Ni (II) with novel tetradentate heteroscorpionate ligand have been synthesized and fully characterized. These complexes showed the ability to oligomerize ethylene upon activation with various organoaluminum compounds (Et2AlCl, Et3Al2Cl3, EtAlCl2, MMAO). Ni (II) based catalytic systems were sufficiently more active (up to 1900 kg·mol (Ni)?1·h?1·atm?1) than Co (II) analogs and have been found to be strongly dependent on the activator composition. The use of PPh3 as an additive to catalytic systems resulted in the increase of activity up to 4,150 kg·mol (Ni)?1·h?1·atm?1 and in the alteration of selectivity. All Ni (II) based systems activated with EtAlCl2 produce up to 5 mol. percent of odd carbon number olefins; two probable mechanisms for their formation are suggested – metathesis and β-alkyl elimination.
- Zubkevich, Sergey V.,Tuskaev, Vladislav A.,Gagieva, Svetlana Ch.,Kayda, Anatoliy S.,Khrustalev, Victor N.,Pavlov, Alexander A.,Zarubin, Dmitry N.,Bulychev, Boris M.
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- Iminobisphosphines to (Non-)symmetrical diphosphinoamine ligands: Metal-induced synthesis of diphosphorus nickel complexes and application in ethylene oligomerisation reactions
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We describe the synthesis of a range of novel iminobisphosphine ligands based on a sulfonamido moiety [R1SO2N=P(R2)2-P(R3)2]. These molecules rearrange in the presence of nickel by metal-induced breakage of the P-P bond to yield symmetrical and nonsymmetrical diphosphinoamine nickel complexes of general formula Ni{[P(R2)2]N(SO2R1)P(R3)2}Br2. The complexes can be isolated and are very stable. Upon activation by MAO, these complexes oligomerise ethylene to small chain oligomers (mainly C4-C8) with high productivity. Surprisingly fast codimerisation reactions of ethylene with butenes is observed, leading to a high content of branched C6 products.
- Boulens, Pierre,Lutz, Martin,Jeanneau, Erwann,Olivier-Bourbigou, Hlne,Reek, Joost N. H.,Breuil, Pierre-Alain R.
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p. 3754 - 3762
(2015/05/05)
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- Hydrodesulfurization of 4,6-dimethyldibenzothiophene over noble metals supported on mesoporous zeolites
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(Figure Presented) Pores for thought: Noble-metal catalysts supported on mesoporous zeolites have been found to be much more efficient than on microporous zeolites and γ-Al2O3 for the hydrodesulfurization of 4,6-dimethyldibenzothioph
- Sun, Yinyong,Prins, Roel
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supporting information; experimental part
p. 8478 - 8481
(2009/04/12)
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- Novel neutral arylnickel(II) phosphine catalysts containing 2-oxazolinylphenolato N-O chelate ligands for ethylene oligomerization and propylene dimerization
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A series of new neutral arylnickel(II) phosphine complexes 1 bearing 2-oxazolinylphenolato ligands [2-(4-R1-5-R2-C3H2NO) -C6H4O]Ni (2-R4-4-R3-C6H3 (PPh3) were synthesized by reactions of sodium salts of 2-(4,5-dihydro-2-oxazolyl)phenol derivatives with trans-Ni(Ar)(Cl (PPh3)2 or by direct reactions of the ligands with trans-Ni(Ar)(Cl)(PPh3)2 in the presence of NEt3. These neutral Ni(II) complexes 1 exhibited high activities and selectivities in ethylene oligomerization and propylene dimerization. The catalytic activities and the product distributions were dependent on the selection of various organoaluminum cocatalysts and phosphine scavenger (Ni(COD)2). The effects of various reaction conditions on ethylene oligomerization were also examined. The highest activity of 5.51×105 g oligomers/(mol Ni · h) and 83% selectivity of C6 internal olefins were obtained in 1a/MAO catalytic system in ethylene oligomerization. The oligomers consisted mainly of lower carbon olefins in the range of C4-C8. Complexes 1 showed the moderate tolerance of polar additives in ethylene oligomerization. The highest activity of 1a/MAO in propylene dimerization reached to 1.32×105 g oligomers/(mol Ni · h).
- Zhao, Wei,Qian, Yanlong,Huang, Jiling,Duan, Jianjun
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p. 2614 - 2623
(2007/10/03)
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- Lewis acid-catalysed reaction of (cyclo)alkenes with oxiranes
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The Lewis acid-catalysed reaction of (cyclo)alkenes with oxiranes can give homologous aldehydes, unsaturated alcohols, and fused furans. Many of these materials are of interest to the fragrance industry. (C) 2000 Elsevier Science Ltd.
- Munro, David,Newman, Chris
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p. 1483 - 1486
(2007/10/03)
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- 1-Hexene Oligomerization in Liquid, Vapor, and Supercritical Phases over Beidellite and Ultrastable Y Zeolite Catalysts
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1-Hexene was oligomerized at 200°C and a pressure of 5 MPa in a down-flow fixed-bed tubular reactor filled with beidellite or ultrastable Y zeolite catalysts. Vapor, liquid, and supercritical states of the reacting hydrocarbons in the reactor tube were established by using propane, pentane, octane, and dodecane as solvents. The initial activity, stability with operation time, and selectivity are very dependent on the physical state of the hydrocarbons. Highest activity and stability are reached in the liquid phase using octane and dodecane solvent. The chain length of the solvent has a strong influence on the deactivation of the catalyst, on the oligomerization selectivity and on the formation of C6 saturates and cracked products.
- Pater, Jerome P. G.,Jacobs, Pierre A.,Martens, Johan A.
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p. 477 - 482
(2007/10/03)
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- Thermal reaction of (CH3)2C=CHCH3 in the presence of di-tert-butyl peroxide: reactions of the radicals (.)CH3 and (CH2)2(.)CCH(CH3)2
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The reaction between the radical (.)CH3 and 2-methylbutene-2 (2MB2) was studied in the temperature range 405-444 K.The (.)CH3 source was di-t-butyl peroxide (PODBT).The rate constants relative to that of recombination were determined for H-abstraction from 2MB2 by (.)CH3 and addition of (.)CH3 to 2MB2: (.)CH3 + (CH3)2C=CHCH3 -> CH4 + (.)CH2CH=CH(CH3)2 (3), -> CH4 + (.)CH2(CH3)C=CHCH3 (4), (.)CH3 + (CH3)2C=CHCH3 -> (CH3)2(.)CCH(CH3)2 (9), 2(.)CH3 -> C2H6 (14).The values are log(k3+4/k141/2 = (3.31+/-0.28) - 34.6+/-3.1)/Θ, log(k9/k141/2) = (3.50+/-0.32) - (36.5+/-3.8)/Θ where Θ = RT ln 10 and the units are dm3/2mol-1/2s-1/2 for k3+4/k141/2 and k9/k141/2 and kJ mol-1 for the energy of activation.For the disproportionation to combination ratios of the 1,1,2-trimethylpropyl radical (112TMP(.)), the following value was obtained: Δ2(112TMP(.),112TMP(.)) = 1.2+/-0.3, where the subscript 2 refers to the formation of a 2-olefin as one of the products. - Keywords: (.)CH3 radical - 1,1,2-trimethylpropyl radical - 2-methylbutene-2 - Gas phase reaction
- Koertvelyesi, T.,Fekete, Z.,Seres, L.
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- Catalytic activity of cluster ruthenium complexes: oligomerization of ethylene
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, one of a series of ruthenium carbonyls tested, shows good catalytic activity in the oligomerization of ethylene in several organic solvents at temperatures above 80 deg C and olefin pressures exceeding 5 atm.Olefin conversions up to 90percent are reached.C4-C12 olefins are the main rection products, with prevalence of the C4 species.Branched isomers are prevalent among the higher oligomers.Evidence has been obtained for a key role for ruthenium hydride intermediates in this catalytic cycle.
- Bianchi, Mario,Menchi, Gloria,Matteoli, Ugo,Piacenti, Franco
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p. 139 - 146
(2007/10/02)
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- METAL COMPLEXES IN CATALYTIC CONVERSIONS OF OLEFINS. 4. HETEROGENIZATION OF NICKEL COMPLEXES ON CHEMICALLY MODIFIED SILOCHROME SURFACE; ACTIVITY AND SELECTIVITY IN ETHYLENE DIMERIZATION
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When activated by Et2AlCl phosphine-containing homogeneous nickel complexes and their heterogenized analogs (HMC) formed on silochrome S-120 modified by NH2 and N(PPh2)2 groups differ significantly in their effectiveness in ethylene dimerization.The catalytic activity of Ni-HMC-Et2AlCl depends on how the HMC was formed.Ni-HMC-I obtained by ligand exchange on chemically modified silochrome is ca. 5-15 times more effective than Ni-HMC-II synthesized from the gas phase.The selectivity in formation of α-olefins (ΣC4 + ΣC6) is ca. 4-5 times higher in the presence of Ni-HMC than for its homogeneous analogs.
- Furman, D. B.,Ivanov, A. O.,Olenin, A. Yu.,Vasil'kov, A. Yu.,Munshieva, M. K.,et al.
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p. 448 - 451
(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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- COMPLEX CATALYSIS. XXVI. CATALYSIS OF THE OLIGOMERIZATION OF ETHYLENE BY CATIONIC ALLYLBIS-LIGAND-NICKEL(II) HEXAFLUOROPHOSPHATE COMPLEXES
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The cationic allylnickel(II) complexes, PF6 with L = P(OPh)3, P(OThym)3, SbPh3, 1/2 COD, were found to be efficient catalysts for the oligomerization of ethylene.The main products are the dimers and trimers.
- Gehrke, Joerg-Peter,Taube, Rudolf,Balbolov, Entscho,Kurtev, Kurty
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- The high pressure photochemistry of alkenes. III. The 184.9 nm photoisomerization processes in acyclic alkenes
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We have made a systematic study of the 184.9 nm photoisomerization of the gaseous acyclic alkenes.Apart from the cis-trans isomerization (geometric isomerization), we have also observed the formation of products arising from the 1,3-hydrogen and methylene shifts (structural isomerization). 1-Alkenes do not show evidence of structural isomerization.This kind of isomerization increases with an increase in the number of alkyl substituents around the double bound.These observations, combined with those from the literature, may be explained on the basis of the following: (a) the 1?,?* state is involved in cis-trans isomerization process; (b) the 1?,R(3s) state is responsible for the methylene shifts; (c) another singlet state is required for the 1,3-hydrogen shift; (d) this last state is either at an energy level higher than that of the Rydberg state or the hot ground state.Finally, the photoexcited molecules, through internal conversion, may convert from one state to another, and their lifetime is long enough to be stabilized by collision.
- Collin, Guy J.,Deslauriers, Helene
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p. 1424 - 1430
(2007/10/02)
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- Hydrocyanation and Hydrogenation of Acetylenes catalysed by Cyanocobaltates
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Acetylenes are regioselectively hydrocyanated by cyanocobaltate prepared at CN:Co -.The preliminary formation of a 3- complex is assumed to explain the fact that the complex is active only at CN:Co 3- which is formed by the reaction of the ?-acetylene complex, rather than acetylene itself, with 3-.
- Funabiki, Takuzo,Yamazaki, Yasuyuki,Sato, Yoshihiro,Yoshida, Satohiro
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p. 1915 - 1918
(2007/10/02)
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- REARRANGEMENT OF CYCLOPROPYL, SUBSTITUTED VINYL AND ALKYL GROUPS TO DIVALENT CARBON.
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The relative carbenic migratory abilities of cyclopropyl, β,β-dimethylvinyl, methyl,ethyl and isopropyl groups have been determined.
- Kraska, A. R.,Cherney, L. I.,Shechter, H.
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p. 2163 - 2166
(2007/10/02)
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- Short-Lived Intermediates. 8. Excited States, Regioselectivity, and Stereospecificity in the Photochemistry of (R,S:S,R)- and (R,R:S,S)-1,2-Dimethylbutyl Trifluoroacetate
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An investigation into the details of the type II photoelimination reaction in racemic (R,S:S,R)- (1a) and racemic (R,R:S,S)-1,2-dimethylbutyl trifluoroacetate (1b) in dodecane solution is presented and contrasted with similar studies of ketones.Stepwise statistical data extraction from quenching (1-dodecene) experiments gave the triplet excited state lifetimes (1a, 0.4; 1b, 2.1 ns), the fraction of reaction from each excited state giving alkene 2 (1a, 77 +/- 8percent singlet; 1b, 78 +/- 2percent singlet) and alkene 3 (1a, 76 +/- 5percent singlet; 1b, 76 +/- 6percent singlet), the regioselectivities of the singlet excited states (1a, 7.4 +/- 0.2; 1b, 4.3 +/- 0.1) and triplet excited states (1a, 6.6 +/- 0.9; 1b, 3.5 +/- 0.6), and stereospecificities of the singlet excited states (1a, 0.88 +/- 0.02; 1b, 0.74 +/- 0.01) and triplet excited states (1a, 0.59 +/- 0.10; 1b, 0.02 +/- 0.11).Dual quenching experiments gave singlet excited state lifetimes (1a, 2.6; 1b, 2.8 ns).The ester type II photoelimination reaction was shown to be markedly similar to analogous reactions in ketones.
- Gano, James E.,Chien, David Hou-Tar
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p. 3182 - 3188
(2007/10/02)
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- Lewis Acid Catalyzed Reactions of Acetylenic Esters with Alkenes. Stereochemistry and Regiochemistry
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The Lewis acid catalyzed reaction of methyl chloropropiolate or dimethyl acetylenedicarboxylate with alkenes leads to ene reactions and/or stereospecific cycloaddition.Ethylaluminum dichloride was found to be a very effective catalyst since it is a strong Lewis acid and an HCl scavenger.With trisubstituted alkenes the ene reaction is regiospecific.A hydrogen is transferred from the alkyl group trans to the alkenyl hydrogen.The regio- and stereoselectivity of the ene reactions of methyl chloropropiolate, methyl propiolate, and dimethyl acetylenedicarboxylate are described.From cyclohexenes, pseudoaxial hydrogens are transferred exclusively.The relative reactivity of alkenes was found to be 1,1-disubstituted > trisubstituted >> monosubstituted and 1,2-disubstituted.The ene adducts and cyclobutenecarboxylates derived from methyl chloropropiolate undergo substitution reactions with organocuprates and can be hydrolyzed to β-keto esters and substituted dimethyl glutarates, respectively.
- Snider, Barry B.,Roush, David M.,Rodini, David J.,Gonzalez, Domingo,Spindell, David
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p. 2773 - 2785
(2007/10/02)
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- Di-μ-carbonyl-tris(cyclopentadienylnickel) as a Cluster Precursor to a Highly Active Ethylene Oligomerization Catalyst
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The first example of the use of a cyclopentadienylnickel cluster to effect catalytic oligomerization of an olefin is reported; when a benzene solution of di-μ-carbonyl-tris(cyclopentadienylnickel) is allowed to react with silica-alumina and subsequently heated to 150 degC, a highly active catalyst is formed which oligomerizes ethylene to higher olefins with turnover frequencies greater than 105 mol ethylene per mol (η5-C5H5)3Ni3(CO)2 per h.
- Beach, David L.,Kobylinski, Thaddeus P.
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p. 933 - 934
(2007/10/02)
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- (Cycloalkylmethyl)bis(η5-cyclopentadienyl)titanium(III) Complexes
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Reaction of bis(cyclopentadienyl)titanium dichloride (1) and isopropylmagnesium bromide (2) with the methylenecycloalkanes 3-8 (cyclopropane), 35 (cyclobutane), and 37 (cyclopentane) leads to the (cycloalkylmethyl)bis(cyclopentadienyl)titanium(III) compounds 9-14, 36, and 38.The cyclopropylmethyl complexes 12-14, which have et least two geminal methyl substituents, are stable.Compounds 9-11, 36, and 38, in which appropriate substituents are lacking, rearrange by ring opening followed by C=C bond isomerization to give the (η3-allyl)bis(η5-cyclopentadienyl)titanium complexes 23-26 and 40.
- Lehmkuhl, Herbert,Fustero, Santos
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p. 1361 - 1370
(2007/10/02)
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