- Kinetics of the Sodium-Ammonia Reduction of 3-Octyne
-
The reduction of 3-octyne by sodium in liquid ammonia was studied kinetically with use of conventional conductometric techniques.The reaction was found to obey the second-order differential rate law-dam->/dt=2kam->.An activation energy of 3.8 +/- 0.9 kcal/mol was calculated.The presence of a weak acid (H2O) markedly increased the reaction rate.A mechanism in which protonation of the radical anion is the rate-determining step is suggested.
- Dewald, Robert R.,Ekstein, Cynthia J.,Song, Woo M.
-
-
Read Online
- Photocatalytic-controlled olefin isomerization over WO3–x using low-energy photons up to 625 nm
-
WO3–x (W-1) was used to achieve controllable photoisomerization of linear olefins without substituents under 625 nm light irradiation. Thermodynamic and kinetic isomers were obtained by regulating the carbon chain length of the olefins. Terminal olefins were converted into isomerized products, and the internal olefin mixtures present in petroleum derivatives were transformed into valuable pure olefin products. Oxygen vacancies (OVs) in W-1 altered the electronic structure of W-1 to improve its light-harvesting ability, which accounted for the high activity of olefin isomerization under light irradiation up to 625 nm. Additionally, OVs on the W-1 surface generated unsaturated W5+ sites that coordinated with olefins for the efficient adsorption and activation of olefins. Mechanistic studies reveal that the in situ formation of surface π-complexes and π-allylic W intermediates originating from the coordination of coordinated unsaturated W5+ sites and olefins ensure high photocatalytic activity and selectivity of W-1 for the photocatalytic isomerization of olefins via a radical mechanism.
- Sun, Xichen,Waclawik, Eric R.,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
-
p. 1641 - 1647
(2021/06/28)
-
- Continuous flow hydrogenation with Pd complexes of pyridine-benzotriazole ligands
-
The use of continuous flow systems in chemical synthesis provides great advantages in terms of sustainability, efficiency, and safety. The ability to control reaction parameters such as temperature, pressure, and catalyst exposure in flow system enables rapid optimization of reaction conditions. In the present study, palladium complexes of 1-(piridin-2-il)-1H-benzo[d][1,2,3]triazol, N-((1H-benzo[d][1,2,3]triazol-1-il)metil)piridin-2-amin, and (1H-benzo[d][1,2,3]triazol-1-yl)(pyridin-2-yl)methanone ligands were synthesized and characterized. The catalytic activities of complexes are investigated in the hydrogenation of various alkenes such as styrene, cyclohexene, and 1-octene under continuous flow conditions. The complexes showed very high activity at 10-bar H2 pressure and 50°C for short periods of 5–10?min. The catalysts reused for 10 cycles with no significant loss of catalytic activity.
- Y?lmaz, Filiz,Hür, Deniz
-
-
- The role of CO2 in the dehydrogenation of n-octane using Cr-Fe catalysts supported on MgAl2O4
-
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.
-
-
- Ni-Catalyzed Isomerization-Hydrocyanation Tandem Reactions: Access to Linear Nitriles from Aliphatic Internal Olefins
-
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
-
supporting information
p. 486 - 490
(2021/02/05)
-
- Regioselective Isomerization of Terminal Alkenes Catalyzed by a PC(sp3)Pincer Complex with a Hemilabile Pendant Arm
-
We describe an efficient protocol for the regioselective isomerization of terminal alkenes employing a previously described bifunctional Ir-based PC(sp3)complex (4) possessing a hemilabile sidearm. The isomerization, catalyzed by 4, results in a one-step shift of the double bond in good to excellent selectivity, and good yield. Our mechanistic studies revealed that the reaction is driven by the stepwise migratory insertion of Ir?H species into the terminal double bond/β-H elimination events. However, the selectivity of the reaction is controlled by dissociation of the hemilabile sidearm, which acts as a selector, favoring less sterically hindered substrates such as terminal alkenes; importantly, it prevents recombination and further isomerization of the internal ones.
- De-Botton, Sophie,Filippov, D.Sc. Oleg A.,Shubina, Elena S.,Belkova, Natalia V.,Gelman, Dmitri
-
p. 5959 - 5965
(2020/10/15)
-
- Graphdiyne-based Pd single-Atom catalyst for semihydrogenation of alkynes to alkenes with high selectivity and conversion under mild conditions
-
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
-
supporting information
p. 20925 - 20930
(2020/11/02)
-
- ALCOHOL DEHYDRATION CATALYST, PREPARATION METHOD THE SAME AND METHOD FOR PREPARING ALPHA-OLEFINS USING THE SAME
-
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.
- -
-
Paragraph 0030; 0132; 0133
(2020/11/24)
-
- Extension of surface organometallic chemistry to metal?organic frameworks: Development of a well-defined single site [(≡Zr? O?)W(=O)(CH2TBu)3] olefin metathesis catalyst
-
We report here the first step by step anchoring of a W(≡CtBu)(CH2tBu)3 complex on a highly crystalline and mesoporous MOF, namely Zr-NU-1000, using a Surface Organometallic Chemistry (SOMC) concept and methodology. SOMC allowed us to selectively graft the complex on the Zr6 clusters and characterize the obtained single site material using state of the art experimental methods including extensive solid-state NMR techniques and HAADF-STEM imaging. Further FT?IR spectroscopy revealed the presence of a W=O moiety arising from the in situ reaction of the W≡CtBu functionality with the coordinated water coming from the 8-connected hexanuclear Zr6 clusters. All the steps leading to the final grafted molecular complex have been identified by DFT. The obtained material was tested for gas phase and liquid phase olefin metathesis and exhibited higher catalytic activity than the corresponding catalysts synthesized by different grafting methods. This contribution establishes the importance of applying SOMC to MOF chemistry to get well-defined single site catalyst on MOF inorganic secondary building units, in particular the in situ synthesis of W=O alkyl complexes from their W carbyne analogues.
- Thiam, Zeynabou,Abou-Hamad, Edy,Dereli, Busra,Liu, Lingmei,Emwas, Abdul-Hamid,Ahmad, Rafia,Jiang, Hao,Isah, Abdulrahman Adamu,Ndiaye, Papa Birame,Taoufik, Mostafa,Han, Yu,Cavallo, Luigi,Basset, Jean-Marie,Eddaoudi, Mohamed
-
supporting information
p. 16690 - 16703
(2020/11/09)
-
- Gem-Dialkyl Effect in Diphosphine Ligands: Synthesis, Coordination Behavior, and Application in Pd-Catalyzed Hydroformylation
-
A series of palladium complexes with C3-bridged bidentate bis(diphenylphosphino)propane ligands with substituents of varying steric bulk at the central carbon have been synthesized. The size of the gem-dialkyl substituents affects the C-C-C bond angles within the ligands and consequently the P-M-P ligand bite angles. A combination of solid-state X-ray diffraction (XRD) and density functional theory (DFT) studies has shown that an increase in substituent size results in a distortion of the 6-membered metal-ligand chair conformation toward a boat conformation, to avoid bond angle strain. The influence of the gem-dialkyl effect on the catalytic performance of the complexes in palladium-catalyzed hydroformylation of 1-octene has been investigated. While hydroformylation activity to nonanal decreases with increasing size of the gem-dialkyl substituents, a change in chemoselectivity toward nonanol via reductive hydroformylation is observed.
- Aitipamula, Srinivasulu,Britovsek, George J. P.,Nobbs, James D.,Romain, Charles,Tay, Dillon W. P.,Van Meurs, Martin,White, Andrew J. P.
-
p. 663 - 671
(2020/01/02)
-
- POCN Ni(ii) pincer complexes: Synthesis, characterization and evaluation of catalytic hydrosilylation and hydroboration activities
-
A series of iminophosphinite POCN pincer Ni(ii) complexes, (POCN)NiMe and (POCN)NiLn(BX4) (L = CH3CN, n = 0, 1; X = F, Ph, C6F5), have been developed and subjected to catalytic hydrosilylation of alkenes, aldehydes and ketones and hydroboration of carbonyl compounds. The stoichiometric reactivity of (POCN)NiMe and (POCN)Ni(BF4) with PhSiH3 and HBPin suggests that catalytic reactions proceed via the hydride intermediate (POCN)NiH. With regard to reactions with HBPin, efficient and mild hydroboration of a variety of carbonyl compounds, including highly chemoselective hydroboration of benzaldehyde in the presence of other common potent reductive functional groups, such as alkenes, alkynes, esters, amides, nitriles, nitro compounds and even ketones, and the first example of base metal catalyzed hydroboration of amides, including mild direct hydroborative reduction of primary and secondary amides to borylated amines were demonstrated for (POCN)NiMe.
- Gudun, Kristina A.,Segizbayev, Medet,Adamov, Assyl,Balanay, Mannix P.,Khalimon, Andrey Y.,Plessow, Philipp N.,Lyssenko, Konstantin A.
-
supporting information
p. 1732 - 1746
(2019/03/07)
-
- Dimerization of Linear Butenes on Zeolite-Supported Ni2+
-
Nickel- and alkali-earth-modified LTA based zeolites catalyze the dimerization of 1-butene in the absence of Br?nsted acid sites. The catalyst reaches over 95% selectivity to n-octenes and methylheptenes. The ratio of these two dimers is markedly influenced by the parallel isomerization of 1-butene to 2-butene, shifting the methylheptene/octene ratio from 0.7 to 1.4 as the conversion increases to 35%. At this conversion, the thermodynamic equilibrium of 90% cis- and trans-2-butenes is reached. Conversion of 2-butene results in methylheptene and dimethylhexene with rates that are 1 order of magnitude lower than those with 1-butene. The catalyst is deactivated rapidly by strongly adsorbed products in the presence of 2-butene. The presence of π-allyl-bound butene and Ni-alkyl intermediates was observed by IR spectroscopy, suggesting both to be reaction intermediates in isomerization and dimerization. Product distribution and apparent activation barriers suggest 1-butene dimerization to occur via a 1′-adsorption of the first butene molecule and a subsequent 1′- or 2′-insertion of the second butene to form octene and methylheptene, respectively. The reaction order of 2 for 1-butene and its high surface coverage suggest that the rate-determining step involves two weakly adsorbed butene molecules in addition to the more strongly held butene.
- Ehrmaier, Andreas,Liu, Yue,Peitz, Stephan,Jentys, Andreas,Chin, Ya-Huei Cathy,Sanchez-Sanchez, Maricruz,Bermejo-Deval, Ricardo,Lercher, Johannes
-
p. 315 - 324
(2019/01/04)
-
- Mechanistic Study of a Re-Catalyzed Monoalkylation of Phenols
-
A mechanistic study of a rhenium catalyzed monoalkylation of phenols is described. Reaction kinetics reveals a zero-order dependence on both alkene and phenol and a half order dependence on catalyst. Isotopic labeling studies, competition experiments, kinetic isotope effects, and Hammett analysis together afford experimental data consistent with a reversible C-H activation step and an irreversible hydrometalation process. The turnover-limiting step is identified as catalyst deaggregation. NMR studies of binary mixtures of catalyst and a single substrate (alkene or phenol) as well as those of reaction mixtures identify potential intermediates and off-cycle species. Despite the numerous Re complexes formed in these mixtures, the overall reaction is both high yielding and highly selective for monoalkylation of phenols.
- Lehnherr, Dan,Wang, Xiao,Peng, Feng,Reibarkh, Mikhail,Weisel, Mark,Maloney, Kevin M.
-
supporting information
p. 103 - 118
(2018/11/06)
-
- Transition metal triflate catalyzed conversion of alcohols, ethers and esters to olefins
-
Herein, we report an efficient transition metal triflate catalyzed approach to convert biomass-based compounds, such as monoterpene alcohols, sugar alcohols, octyl acetate and tea tree oil, to their corresponding olefins in high yields. The reaction proceeds through C-O bond cleavage under solvent-free conditions, where the catalytic activity is determined by the oxophilicity and the Lewis acidity of the metal catalyst. In addition, we demonstrate how the oxygen containing functionality affects the formation of the olefins. Furthermore, the robustness of the used metal triflate catalysts, Fe(OTf)3 and Hf(OTf)4, is highlighted by their ability to convert an over 2400-fold excess of 2-octanol to octenes in high isolated yields.
- Keskiv?li,Parviainen,Lagerblom,Repo
-
p. 15111 - 15118
(2018/05/04)
-
- Alkene Isomerization-Hydroboration Catalyzed by First-Row Transition-Metal (Mn, Fe, Co, and Ni) N-Phosphinoamidinate Complexes: Origin of Reactivity and Selectivity
-
We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)2) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+ d5-d8) in the isomerization-hydroboration of 1-octene, cis-4-octene, or trans-4-octene (1a-c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)2, (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6-iPr2C6H3) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydroboration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formation of putative (PN)Ni(H2BPin) is reversible. Conversely, poor catalytic performance was noted for ((PN)NiH)2 and (PN)NiH(L) (L = pyridine or DMAP). Using DFT calculations, the relative reactivity of (PN)M precatalysts was found to be a function of their spin-state energy gaps. For reaction of (PN)MnH with trans-4-octene (1c) there is no viable spin crossover mechanism and migratory insertion is slow, resulting in poor reaction yields. In contrast, (PN)FeH can access a lower barrier through spin crossover, whereas (PN)CoH has a very low migratory insertion barrier from its low spin state. While (PN)NiH has a reasonable migratory insertion barrier, it is plausible that off-catalytic cycle intermediates are responsible for the diminished reaction rate and product yields that are observed experimentally. On the basis of the computed isomerization and borylation energy landscapes, a Curtin-Hammett-type scenario with fast isomerization through β-hydride elimination and migratory insertion steps is proposed, giving rise to a catalytic equilibrium of isomeric (PN)M(octyl) resting states, followed by slow product-forming borylation. The significantly lower barriers calculated for borylation of terminal (PN)M(n-octyl) species versus isomeric internal (PN)M(CHR2) intermediates provides a rationale for the experimentally observed terminal isomerization-hydroboration selectivity.
- Macaulay, Casper M.,Gustafson, Samantha J.,Fuller, Jack T.,Kwon, Doo-Hyun,Ogawa, Takahiko,Ferguson, Michael J.,McDonald, Robert,Lumsden, Michael D.,Bischof, Steven M.,Sydora, Orson L.,Ess, Daniel H.,Stradiotto, Mark,Turculet, Laura
-
p. 9907 - 9925
(2018/10/15)
-
- NCP ligand, [...] complex, synthesis method, intermediate and application
-
The invention discloses an NCP ligand, iridium complex, synthetic method, intermediate and application thereof. The invention provides an NCP ligand and an NCP ligand iridium complex, wherein R1, R2, R3, R4, R5, R6 and R7 separately represent hydrogen atom or C1-C30 alkyl, R' and R'' independently represent C1-C30 alkyl. The invention provides the application of the NCP ligand iridium complex to the catalysis of alkane dehydrogenation reaction, olefin isomerization reaction, alcohol dehydrogenation reaction, ester alpha alkylation reaction, and amide alpha alkylation reaction. The NCP ligand provided by the invention contains dialkyl substituted phosphine, which has strong electron donating ability and can form a NCP ligand iridium complex by complexing with iridium. The NCP ligand iridium complex uses pyridine to replace a conventional alkyl phosphate electron donor, and has the advantages of good stability, high selectivity on alkane dehydrogenation reaction, mild reaction conditions, good catalytic effect, and industrial production prospect.
- -
-
Paragraph 0103; 0197-0199
(2018/07/30)
-
- Thermal, Catalytic Conversion of Alkanes to Linear Aldehydes and Linear Amines
-
Alkanes, the main constituents of petroleum, are attractive feedstocks for producing value-added chemicals. Linear aldehydes and amines are two of the most important building blocks in the chemical industry. To date, there have been no effective methods for directly converting n-alkanes to linear aldehydes and linear amines. Here, we report a molecular dual-catalyst system for production of linear aldehydes via regioselective carbonylation of n-alkanes. The system is comprised of a pincer iridium catalyst for transfer-dehydrogenation of the alkane using t-butylethylene or ethylene as a hydrogen acceptor working sequentially with a rhodium catalyst for olefin isomerization-hydroformylation with syngas. The system exhibits high regioselectivity for linear aldehydes and gives high catalytic turnover numbers when using ethylene as the acceptor. In addition, the direct conversion of light alkanes, n-pentane and n-hexane, to siloxy-terminated alkyl aldehydes through a sequence of Ir/Fe-catalyzed alkane silylation and Ir/Rh-catalyzed alkane carbonylation, is described. Finally, the Ir/Rh dual-catalyst strategy has been successfully applied to regioselective alkane aminomethylation to form linear alkyl amines.
- Tang, Xinxin,Jia, Xiangqing,Huang, Zheng
-
supporting information
p. 4157 - 4163
(2018/03/29)
-
- NiH-Catalyzed Reductive Relay Hydroalkylation: A Strategy for the Remote C(sp3)?H Alkylation of Alkenes
-
The terminal-selective, remote C(sp3)?H alkylation of alkenes was achieved by a relay process combining NiH-catalyzed hydrometalation, chain walking, and alkylation. This method enables the construction of unfunctionalized C(sp3)?C(sp3) bonds under mild conditions from two simple feedstock chemicals, namely olefins and alkyl halides. The practical value of this transformation is further demonstrated by the large-scale and regioconvergent alkylation of isomeric mixtures of olefins at low catalyst loadings.
- Zhou, Fang,Zhu, Jin,Zhang, Yao,Zhu, Shaolin
-
supporting information
p. 4058 - 4062
(2018/03/21)
-
- Catalyst versus Substrate Control of Forming (E)-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
-
Here we examine in detail two catalysts for their ability to selectively convert 1-alkenes to (E)-2-alkenes while limiting overisomerization to 3- or 4-alkenes. Catalysts 1 and 3 are composed of the cations CpRu(κ2-PN)(CH3CN)+ and Cp?Ru(κ2-PN)+, respectively (where PN is a bifunctional phosphine ligand), and the anion PF6-. Kinetic modeling of the reactions of six substrates with 1 and 3 generated first- and second-order rate constants k1 and k2 (and k3 when applicable) that represent the rates of reaction for conversion of 1-alkene to (E)-2-alkene (k1), (E)-2-alkene to (E)-3-alkene (k2), and so on. The k1:k2 ratios were calculated to produce a measure of selectivity for each catalyst toward monoisomerization with each substrate. The k1:k2 values for 1 with the six substrates range from 32 to 132. The k1:k2 values for 3 are significantly more substrate-dependent, ranging from 192 to 62 000 for all of the substrates except 5-hexen-2-one, for which the k1:k2 value was only 4.7. Comparison of the ratios for 1 and 3 for each substrate shows a 6-12-fold greater selectivity using 3 on the three linear substrates as well as a >230-fold increase for 5-methylhex-1-ene and a 44-fold increase for a silyl-protected 4-penten-1-ol substrate, which are branched three and five atoms away from the alkene, respectively. The substrate 5-hexen-2-one is unique in that 1 was more selective than 3; NMR analysis suggested that chelation of the carbonyl oxygen can facilitate overisomerization. This work highlights the need for catalyst developers to report results for catalyzed reactions at different time points and shows that one needs to consider not only the catalyst rate but also the duration over which a desired product (here the (E)-2-alkene) remains intact, where 3 is generally superior to 1 for the title reaction.
- Paulson, Erik R.,Delgado, Esteban,Cooksy, Andrew L.,Grotjahn, Douglas B.
-
supporting information
p. 1672 - 1682
(2019/01/04)
-
- Effect of Carboxylate Ligands on Alkane Dehydrogenation with (dmPhebox)Ir Complexes
-
A series of carboxylate-ligated iridium complexes (dmPhebox)Ir(O2CR)2(H2O) (R = -CH3, -CH2CH3, -CMe3, -CH2C6H5, and -CH=CMe2) were designed and synthesized to understand the carboxylate ligand effects on the reactivity of the complex for alkane dehydrogenation. Kinetic studies showed that the different R groups of the carboxylate iridium complexes can affect the reactivity with octane in the β-H elimination step. The rate constants for octene formation with different carboxylate ligands follow the order R = -CH=CMe2 > -CMe3 > -CH2CH3 > -CH3 > -CH2C6H5. In contrast, there is no significant effect of carboxylate ligand on the rate of the C-H activation step at 160 °C. These experimental results support the findings in the previously reported density functional theory study of the (dmPhebox)Ir complex in alkane C-H activation.
- Yuan, Hongmei,Brennessel, William W.,Jones, William D.
-
p. 2326 - 2329
(2018/03/13)
-
- New palladium (II) complexes with Thiophene and furan bridged N-Acylbenzotriazole ligands: Synthesis, characterization and hydrogenation activity in ionic liquid
-
Palladium complexes of N-acylbenzotriazole derivative ligands were synthesized and characterized. The catalytic activities of complexes of ([PdL1(OAc)2] and [PdL2(OAc)2]) were investigated in relation to hydrogenation reactions of styrene, 1-octene and cyclohexene in [bmim][BF4] as greener reaction media. 100% ethyl benzene conversion was obtained with both complexes in 1?h reaction time. Additionally, 100% 1-octene conversion was reached within the same period of time with [PdL2(OAc)2] complex. In cyclohexene hydrogenation, product formation reached up to 67% at 363?K with [PdL1(OAc)2] complex. Reusability tests were conducted under the highest product conversion conditions, and both catalysts were found to be efficient up to 5?cycles for all substrates. The other reaction parameters such as solvent effect, H2 (g) pressure, ns/nc ratio were also investigated.
- ünver, Hakan,Yilmaz, Filiz
-
p. 875 - 880
(2017/06/29)
-
- Tuning the Porphyrin Building Block in Self-Assembled Cages for Branched-Selective Hydroformylation of Propene
-
Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris(meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second-generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second-generation assembly.
- Wang, Xiaowu,Nurttila, Sandra S.,Dzik, Wojciech I.,Becker, René,Rodgers, Jody,Reek, Joost N. H.
-
supporting information
p. 14769 - 14777
(2017/09/06)
-
- Phosphoramidite complexes of Pd(II), Pt(II) and Rh(I): An effective hydrosilylation catalyst of 1-hexyne and 1-octene
-
The hydrophosphorane HP(OC6H4NMe)2 was used to prepare the diastereotopic complexes [MCl2{P(OC6H4NMe)OC6H4NHMe}] (M?=?Pd, Pt) by reaction with [MCl2(PhCN)2], and [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] by reaction with [RhCl(PPh3)3]. To form these complexes, the phosphorane undergoes ring-opening, whereby it is coordinated as the tautomeric neutral phosphoramidite-amino chelating ligand. The crystal structure of [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was determined and the geometry about the Rh(I) atom is square-planar with cis-disposed phosphorus-donor ligands. The Rh–P distance is shortened (2.1056(6) ?) due to Rh(d)?→?P π-backbonding. In addition, [RhCl(PPh3){P(OC6H4NMe)OC6H4NHMe}] was shown to be an effective regio- and stereoselective catalyst for the hydrosilylation of 1-octene and 1-hexyne.
- Carroll, Hannah K.,Parlane, Fraser G.L.,Reich, Noah,Jelier, Benson J.,Montgomery, Craig D.
-
-
- Terminal alkene monoisomerization catalysts and methods
-
The invention provides novel catalysts and methods of using catalysts for controlling the position of a double bond and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers. Catalysts such as (pentamethylcyclopentadienyl)Ru formulas 1 and 3 having a bifunctional phosphine can be used in the methods. A catalyst loading of 1 mol % of formulas 1+3 can be employed for the production of (E)-2-alkenes at 40-70° C.; lower temperatures can be used with higher catalyst loading. Acetonitrile-free catalysts can be used at lower loadings, room temperature, and in less than a day to accomplish the same results as catalysts 1+3. The novel catalyst systems minimize thermodynamic equilibration of alkene isomers, so that the trans-2-alkenes of both non-functionalized and functionalized alkenes can be generated.
- -
-
Page/Page column 38; 39
(2017/08/07)
-
- Synthesis, characterization, and reactivities of molybdenum and tungsten PONOP pincer complexes
-
A new series of molybdenum and tungsten tricarbonyl pincer complexes, bearing pyridine-based PONOP-type pincer ligands, have been synthesized and fully characterized. Addition of HBF4·Et2O to these tricarbonyl complexes generated seven-coordinate molybdenum and tungsten hydride complexes, and these compounds have been isolated in good yields. These metal hydrides show fluxional behavior in solution. The hydride ligands on these metal complexes are acidic in nature and are readily deprotonated by bases. The molybdenum hydride complex is shown to catalyze isomerization of 1-hexene to internal isomers under mild conditions.
- Castro-Rodrigo, Ruth,Chakraborty, Sumit,Munjanja, Lloyd,Brennessel, William W.,Jones, William D.
-
supporting information
p. 3124 - 3131
(2016/10/09)
-
- Metathesis of C5–C8 Terminal Olefins on Re2O7/Al2O3 Catalysts
-
Abstract: Primary products of the interaction of terminal olefins C5–C8 with Re2O7/Al2O3 catalysts are established. The rupture of the C=C bond of the olefin occurs with formation of a carbene localized at a rhenium ion, with the alkylidene fragment in the produced carbene being the CH2=group of the terminal alkene molecule. Thus M=CH2 species and lower normal α-olefins are formed. Graphical Abstract: [Figure not available: see fulltext.]
- Kustov, Leonid M.,Furman, Daniil B.,Barkova, Aleksandra P.
-
p. 1033 - 1039
(2016/06/01)
-
- PROCESS FOR DEHYDROGENATION OF ALKYL-CONTAINING COMPOUNDS USING MOLYBDENUM AND TUNGSTEN NITROSYL COMPLEXES
-
A process for the dehydrogenation of alkyl-containing compounds comprises reacting an alkyl-containing compound and a Group VI nitrosyl complex characterized as a transition metal complex having the composition Cp'M(NO)(R1)(R2), wherein Cp' is selected from certain substituted and unsubstituted η5-cyclopentadienyl groups; M is W or Mo; and R1 and R2 are independently selected from CH2C(CH3)3; CH2Si(CH3)3; CH2(C6H5); CH3; hydrogen; and η3-allyl; provided that if R1 is hydrogen, R2 is η3-allyl; under conditions such that the alkyl-containing compound is converted to an olefin, and in particular embodiments, a terminal olefin. The dehydrogenation can be carried out using a neat and/or undried alkyl-containing compound and/or may be conducted under air, and does not require a sacrificial olefin to drive the reaction, thereby increasing convenience and decreasing cost in comparison with some other dehydrogenation processes.
- -
-
Page/Page column 8
(2016/08/10)
-
- Acid-catalysed carboxymethylation, methylation and dehydration of alcohols and phenols with dimethyl carbonate under mild conditions
-
Dimethyl carbonate (DMC) chemistry has been extended to include acid-catalysed reactions of different aliphatic alcohols and phenols. For the first time, p-toluenesulfonic acid (PTSA), H2SO4, AlCl3 and FeCl3 have been shown to aid carboxymethylation for primary aliphatic alcohols at catalytic loadings with quantitative conversion and selectivity. For carboxymethylation of secondary alcohols, stoichiometric PTSA and catalytic AlCl3 both gave quantitative conversion and selectivity. Stoichiometric FeCl3 and H2SO4 promoted dehydration of linear aliphatic alcohols. Additionally FeCl3 catalysed methylation of cyclohexanol, whilst AlCl3 resulted in methylation of phenolic compounds. This research expands the range of potential application for DMC in green chemistry.
- Jin, Saimeng,Hunt, Andrew J.,Clark, James H.,McElroy, Con Robert
-
supporting information
p. 5839 - 5844
(2016/11/06)
-
- Insertion, elimination and isomerisation of olefins at alkylaluminium hydride: An experimental and theoretical study
-
The insertion, elimination and isomerisation of octenes with di-n-octylaluminium hydride [HAl(Oct)2], tri-n-octylaluminium [Al(Oct)3] and sec-octylaluminium species have been studied as individual steps in a putative aluminium based contrathermodynamic olefin isomerisation process. While elimination of 1-octene from [Al(Oct)3] is energetically unfavourable, the process is driven by high temperature vacuum distillation, leading to very high selectivity to 1-octene (>97%). At high conversions the [HAl(Oct)2] so obtained exists predominately as hydride-bridged cyclic oligomers, whereas at low conversion the mixed alkyl/hydride-bridged dimer [(Oct)2Al(μ-H)(μ-Oct)Al(Oct)2] is the major species. Di-n-octylaluminium hydride recovered after olefin elimination may be recycled and is active toward re-insertion of octenes. Internal octenes (cis- and trans-2-, 3- and 4-octene) only partially insert however, and even after prolonged heating there is no significant secondary to primary alkyl isomerisation evident.
- Weliange, Nandita M.,McGuinness, David S.,Gardiner, Michael G.,Patel, Jim
-
p. 15286 - 15296
(2015/09/01)
-
- Mesoporous silico-aluminophosphates derived from microporous precursors as promising catalyst for hydroisomerization
-
A series of mesoporous silicoaluminophosphates (MESO-SAPOs) with different silica contents were synthesized using the microporous precursors of SAPO-37 (MESO-SAPO-37). Various analytical and spectroscopic techniques revealed the presence of mesoporous and microporous properties of the materials. The resulting materials were applied to vapor-phase hydroisomerization of 1-octene to afford the corresponding branched alkenes in good yields under ambient conditions. The catalytic activity of MESO-SAPO-37 was compared to those of other mesoporous analogs obtained from SAPO-34 and SAPO-5 precursors. Among all the synthesized materials, MESO-SAPO-37 showed the best catalytic activity owing to the presence of faujasite units.
- Yadav, Rekha,Singh, Arvind Kumar,Sakthivel, Ayyamperumal
-
p. 155 - 162
(2015/03/04)
-
- Lewis Acid Enhanced Ethene Dimerization and Alkene Isomerization - ESI-MS Identification of the Catalytically Active Pyridyldimethoxybenzimidazole Nickel(II) Hydride Species
-
A cationic methallyl 2-pyridine-4,7-dimethoxybenzimidazole (L1) nickel precatalyst is highly selective in ethene dimerizations to 1-butene. The same catalyst isomerizes 1-butene and 1-octene to internal olefins. Co-catalytic additives of B(C6F5)3 or BF3·OEt2 coordinate to the catalyst and increase the reaction rates of ethene dimerization. ESI-MS was applied identifying a [L1NiH]+ cation as the catalytically active species.
- Escobar, Manuel A.,Trofymchuk, Oleksandra S.,Rodriguez, Barbara E.,Lopez-Lira, Claudia,Tapia, Ricardo,Daniliuc, Constantin,Berke, Heinz,Nachtigall, Fabiane M.,Santos, Leonardo S.,Rojas, Rene S.
-
p. 7338 - 7342
(2015/12/11)
-
- Oligomerization of 1-butene with a homogeneous catalyst system based on allylic nickel complexes
-
The oligomerization of 1-butene with a nickel-based catalyst system constitutes an elegant synthesis method for obtaining linear octenes from readily available chemicals. It is well known that the bis-(cyclooctadiene)nickel(0)-complex (Ni(COD)2) can be used in combination with 1,1,1,5,5,5-hexafluoroacetylacetone (hfacac) forming [Ni-1] as a catalyst for the dimerization of 1-butene, which produces a linear octene yield of 75-83% at reaction temperatures between 70-80 °C. We are the first to demonstrate that it is also possible to use allylic nickel complexes in combination with hfacac to produce linear octenes with a selectivity of 70% under very mild reaction conditions and at low catalyst concentrations. Additionally the catalyst can be formed simply by adding the activator hfacac to a solution of the allylic nickel complex. No complicated synthesis or purification is needed.
- Behr,Bayrak,Peitz,Stochniol,Maschmeyer
-
p. 41372 - 41376
(2015/05/27)
-
- Insertion and isomerisation of internal olefins at alkylaluminium hydride: Catalysis with zirconocene dichloride
-
The insertion of internal olefins (hydroalumination) and chain walking isomerisation at di-n-octylaluminium hydride [Al(Oct)2H], promoted by zirconocene dichloride [Cp2ZrCl2] has been studied. The reaction between [Cp2ZrCl2] and [Al(Oct)2H] in non-polar solvents leads to clusters containing bridging hydride ligands between Zr and Al. This system promotes hydroalumination of 1-octene but is largely ineffective for internal octenes (2-, 3-, 4-octene). In tetrahydrofuran the Zr-Al hydride clusters formed are more reactive and catalyse insertion and isomerisation of internal olefins to primary metal-alkyls, although this is accompanied by catalyst deactivation. Elimination and removal of 1-octene from the system post insertion/isomerisation was attempted, but it was found that the presence of the Zr catalyst leads to back-isomerisation to internal octenes, along with further decomposition with n-octane formation. Some possible pathways of catalyst decomposition, involving reduction of Zr and alkane elimination, have been studied theoretically.
- Weliange, Nandita M.,McGuinness, David S.,Gardiner, Michael G.,Patel, Jim
-
p. 20098 - 20107
(2015/12/01)
-
- Multifunctional, defect-engineered metal-organic frameworks with ruthenium centers: Sorption and catalytic properties
-
A mixed-linker solid-solution approach was employed to modify the metal sites and introduce structural defects into the mixed-valence Ru II/III structural analogue of the well-known MOF family [M 3II,II(btc)2] (M=Cu, Mo, Cr, Ni, Zn; btc=benzene-1,3,5-tricarboxylate), with partly missing carboxylate ligators at the Ru2 paddle-wheels. Incorporation of pyridine-3,5-dicarboxylate (pydc), which is the same size as btc but carries lower charge, as a second, defective linker has led to the mixed-linker isoreticular derivatives of Ru-MOF, which display characteristics unlike those of the defect-free framework. Along with the creation of additional coordinatively unsaturated sites, the incorporation of pydc induces the partial reduction of ruthenium. Accordingly, the modified Ru sites are responsible for the activity of the defective variants in the dissociative chemisorption of CO 2, the enhanced performance in CO sorption, the formation of hydride species, and the catalytic hydrogenation of olefins. The defect engineering in Ru-based metal-organic frameworks (MOFs) at coordinatively unsaturated metal centers (CUS) induces partial reduction of the metal nodes and leads to properties that are absent for the parent MOF, such as dissociative chemisorption of CO2 and enhanced sorption capacity of CO. The modified MOFs offer new perspectives as multifunctional materials whose performance is controlled by design of the defects.
- Kozachuk, Olesia,Luz, Ignacio,Llabres I Xamena, Francesc X.,Noei, Heshmat,Kauer, Max,Albada, H. Bauke,Bloch, Eric D.,Marler, Bernd,Wang, Yuemin,Muhler, Martin,Fischer, Roland A.
-
supporting information
p. 7058 - 7062
(2014/07/08)
-
- Z -selective alkene isomerization by high-spin cobalt(II) complexes
-
The isomerization of simple terminal alkenes to internal isomers with Z-stereochemistry is rare, because the more stable E-isomers are typically formed. We show here that cobalt(II) catalysts supported by bulky β-diketiminate ligands have the appropriate kinetic selectivity to catalyze the isomerization of some simple 1-alkenes specifically to the 2-alkene as the less stable Z-isomer. The catalysis proceeds via an "alkyl" mechanism, with a three-coordinate cobalt(II) alkyl complex as the resting state. β-Hydride elimination and [1,2]-insertion steps are both rapid, as shown by isotopic labeling experiments. A steric model explains the selectivity through a square-planar geometry at cobalt(II) in the transition state for β-hydride elimination. The catalyst works not only with simple alkenes, but also with homoallyl silanes, ketals, and silyl ethers. Isolation of cobalt(I) or cobalt(II) products from reactions with poor substrates suggests that the key catalyst decomposition pathways are bimolecular, and lowering the catalyst concentration often improves the selectivity. In addition to a potentially useful, selective transformation, these studies provide a mechanistic understanding for catalytic alkene isomerization by high-spin cobalt complexes, and demonstrate the effectiveness of steric bulk in controlling the stereoselectivity of alkene formation.
- Chen, Chi,Dugan, Thomas R.,Brennessel, William W.,Weix, Daniel J.,Holland, Patrick L.
-
supporting information
p. 945 - 955
(2014/02/14)
-
- Iridium complexes of new NCP pincer ligands: Catalytic alkane dehydrogenation and alkene isomerization
-
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
-
supporting information
p. 11056 - 11059
(2014/09/30)
-
- General catalyst control of the monoisomerization of 1-alkenes to trans -2-alkenes
-
After searching for the proper catalyst, the dual challenges of controlling the position of the double bond, and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers are finally met in a general sense by mixtures of (C5Me5)Ru complexes 1 and 3 featuring a bifunctional phosphine. Typically, catalyst loadings of 1 mol % of 1 and 3 can be employed for the production of (E)-2-alkenes at 40-70 C. Catalyst comprising 1 and 3 avoids more than any other known example the thermodynamic equilibration of alkene isomers, as the trans-2-alkenes of both nonfunctionalized and functionalized alkenes are generated.
- Larsen, Casey R.,Erdogan, Gulin,Grotjahn, Douglas B.
-
supporting information
p. 1226 - 1229
(2014/02/14)
-
- NCN TRIANIONIC PINCER COMPLEXES AS CATALYSTS FOR OLEFIN POLYMERIZATION AND ISOMERIZATION
-
A catalyst comprising a NCN pincer ligand group VI complex is capable of being used as an olefin polymerization or isomerization catalyst that does not require an expensive cocatalyst. The complex has the NCN pincer ligand in a trianionic form with the group VI in the +3 oxidation state or the +4 oxidation state and complexed to an anionic hydrocarbon group, or the complex has the NCN pincer ligand in a dianionic form with the group VI in the +2 oxidation state. The complex is capable of initiating the polymerization of alkenes without an added activator. The presence of a water scavenger and activator or cocatalyst, such as triisobutylaluminum, increases the catalytic activity. The complex is capable of selectively isomerizing 1-alkenes to cis/trans 2-alkenes.
- -
-
Paragraph 0038-0041
(2013/11/06)
-
- Unique mesoporous silicoaluminophosphate assembled from faujasite-type SAPO-37 precursor: A potential catalyst for isomerization
-
Unique mesoporous silicoaluminophosphate (MESO-SAPO-37) with uniform pores (3 nm) was synthesized for the first time by using a faujasite-type microporous SAPO-37 precursor. MESO-SAPO-37 contains hierarchical mesopores with a microporous secondary building unit. It possesses strong acidity and shows high catalytic activity for the conversion of 1-octene, with the exclusive formation of isomerized products (84%).
- Yadav, Rekha,Singh, Arvind Kumar,Sakthivel, Ayyamperumal
-
supporting information
p. 1160 - 1162
(2013/10/22)
-
- Highly active hydroformylation catalysts: Synthesis, characterisation and catalytic performance
-
The phoszone ligand [(Ph2P)(bis-3,5-CF3-Ph)]NN= CH(penta-fluoro-Ph) transformed in liquid CO2 at room temperature in presence of [Rh(cod)2]OTf into [Rh(cod)(η2-P,P′- Ph2POPPh2)]OTf. Replacing the O-atom in Ph 2POPPh2 by a PrN-group leads to the ligand PrN(PPh 2)2 acting similarly as a bidentate ligand in [Rh(cod)(η2-P,P′-PrN(PPh2)2)]OTf. Hydroformylation of 1-octene with in situ catalysts formed by the ligands with [Rh(cod)2]OTf showed hydroformylation activities at 50 % conversion of 16,000 h-1 (PrN(PPh2)2/[Rh(cod) 2]OTf) and 24,000 h-1 (phoszone/[Rh(cod)2]OTf), respectively.
- Piras, Elisabetta,Powietzka, Bernhard,Wurst, Frederik,Neumann-Walter, Doreen,Gruetzmacher, Hans-Joerg,Otto, Thomas,Zevaco, Thomas,Walter, Olaf
-
p. 673 - 680
(2013/07/26)
-
- Graphite oxide activated zeolite NaY: Applications in alcohol dehydration
-
A mixture of graphite oxide (GO) and the zeolite NaY (Si/Al = 5.1) was used to dehydrate various alcohols to their respective olefinic products. Using conditions optimized for 4-heptanol (15 wt% GO-NaY (1 : 1 wt/wt), 150°C, 30 min), a series of secondary and tertiary aliphatic alcohols were cleanly dehydrated in moderate to excellent conversions (27.5-97.2%). Several primary alcohols were also dehydrated, although higher catalyst loadings (200 wt% GO-NaY (1 : 1) and longer reaction times (3 h) were required. The enhanced dehydration activity was attributed to the ability of GO to convert NaY to an acidic form and without the need for ammonium cation exchange and/or high temperature calcination. The Royal Society of Chemistry 2013.
- Todd, Alexander D.,Bielawski, Christopher W.
-
p. 135 - 139
(2013/03/29)
-
- Synthesis, characterization, and catalytic behavior of dioxomolybdenum complexes bearing AcAc-type ligands
-
A series of [MoO2(acac′)2] [acac′ = acetylacetonato-type ligand: dibenzoylmethane (3), 1-benzoylacetone (4), bis(p-methoxybenzoyl)methane (5), 2-acetylcyclopentanone (6), 2-acetylcyclohexanone (7), and 2-acetyl-1-tetralone (8)] complexes have been synthesized in yields of 44-83 % by a simple synthetic method by using sodium molybdate and the desired acac-type ligand as starting materials. All the complexes were characterized by IR, UV/Vis, NMR, and high-resolution ESI-MS, and for compounds 3, 4, and 8, solid-state structures were obtained by X-ray diffraction. All the complexes contain a cis-dioxomolybdenum moiety, as proven by the characteristic Mo=O vibrations in the IR spectra and the occurrence of four sets of signals in the NMR spectra of the complexes bearing asymmetrical ligands (4 and 6-8), and confirmed by the solid-state structures. The complexes were found to be active as catalysts in the dehydration of 1-phenylethanol to styrene using technical-grade toluene as the solvent in air at 100 °C. The highest catalytic activity was found for [MoO2{(tBuCO) 2CH}2] (2), followed by [MoO2{(C 6H5CO)2CH}2] (3). Both complexes were also found to be active in the dehydration of other alcohols, including allylic, aliphatic, and homoallylic alcohols, as well as secondary and tertiary alcohols, with 2 generally showing better activity and selectivity than 3. These catalytic results were compared with those previously obtained with the metal-based catalyst Re2O7 and the benchmark acid catalyst H2SO4. The results were dependent on the substrate: By using 2, good selectivities but lower activities were generally obtained with tertiary alcohols, whereas good activities but lower selectivities were obtained with secondary alcohols. The industrially important dehydration of 2-octanol to octenes was very efficiently catalyzed by 2. Overall, the [MoO 2(acac′)2] complexes reported herein could offer a cheaper and more abundant metal-based catalyst alternative to the previously reported rhenium-based catalytic system for the dehydration reaction. Copyright
- Korstanje, Ties J.,Folkertsma, Emma,Lutz, Martin,Jastrzebski, Johann T.B.H.,Klein Gebbink, Robertus J.M.
-
p. 2195 - 2204
(2013/05/22)
-
- Alkane dehydrogenation by C-H activation at iridium(III)
-
Stoichiometric alkane dehydrogenation utilizing an IrIII pincer complex, (dmPhebox)Ir(OAc)2(OH2) (1a), has been described. The reaction between 1a and octane resulted in quantitative formation of (dmPhebox)Ir(OAc)(H) (3a) and octene. At early reaction times 1-octene is the major product, indicative of terminal C-H activation by 1a. In contrast to prior reports of alkane dehydrogenation with Ir, C-H bond activation occurs at IrIII and the dehydrogenation is not inhibited by nitrogen, olefin, or water.
- Allen, Kate E.,Heinekey, D. Michael,Goldman, Alan S.,Goldberg, Karen I.
-
supporting information
p. 1579 - 1582
(2013/05/08)
-
- Rh(i) complexes supported on a biopolymer as recyclable and selective hydroformylation catalysts
-
Chitosan-supported Rh complexes were prepared in a stable form to form new catalysts and have been characterized using elemental analysis, UV-vis, FT-IR, ICP-MS, PXRD, solid state 31P and 13C NMR spectroscopy and TEM. Mononuclear Rh(i) complexes (as models for the heterogenized catalysts) were also prepared via the Schiff-base condensation reaction and the crystal structure of the cyclohexyl iminophosphine Rh(i) complex was elucidated. The chitosan-supported Rh complexes and mononuclear analogues are active catalysts in the hydroformylation of 1-octene with optimal reaction conditions realized at 75 °C and 30 bar syngas pressure. Under these conditions, 1-octene conversion to the desired linear aldehydes was observed and the best selectivity in this regard was shown by the supported iminophosphine-based rhodium catalyst. Overall, the supported catalysts showed similar chemo- and regioselectivities in comparison to their mononuclear counterparts but where more stable, being reused up to four times without loss of activity and selectivity.
- Makhubela, Banothile C. E.,Jardine, Anwar,Smith, Gregory S.
-
supporting information; experimental part
p. 338 - 347
(2012/04/10)
-
- Catalytic oxidation of n-octane over cobalt substituted ceria (Ce 0.90Co0.10O2-δ) catalysts
-
Catalytic oxidative activation of octane was carried out in the presence of Co substituted ceria catalysts of the type Ce1-xCoxO 2-δ (Ce0.90Co0.10O2-δ). The catalysts were synthesized by the solution combustion method and the surface characteristics were determined by BET, powder XRD, structural refinement and XPS. The synthesized catalyst crystallizes with a fluorite structure, the crystallinity was confirmed by bright-field images of TEM. Hydrogen uptake studies show a strong reduction peak at 425 °C and it proves substitution of cobalt ions inside the matrix of the lattice system. X-ray photoelectron spectroscopy (XPS) clarified that even though under reduction conditions, the cerium ions were slightly oxidized because of the sequence of standard reduction potentials of both cerium and cobalt ions. The catalytic activity of the catalyst was investigated between the temperature range from 350 to 550 °C, in a continuous flow fixed bed reactor at GHSV 4000 h-1 with varying n-octane to oxygen molar ratios from 1:0.5 to 1:2.5. Results show that the conversion and selectivity of products (alkenes, oxygenates, aromatics, carbon oxides and cracked products) from the n-octane varies consequently with n-octane to oxygen molar ratio. The product selectivity at iso-conversion for C 8 products, aromatics, oxygenates and octenes was determined. The catalyst shows higher activity with respect to an increase in the n-octane to oxygen molar ratio and reaction temperature.
- Narayanappa, Mahadevaiah,Dasireddy, Venkata D.B.C.,Friedrich, Holger B.
-
p. 135 - 143
(2013/02/25)
-
- Biphasic hydroformylation of 1-octene catalyzed by cobalt complex of trisulfonated tris(biphenyl)phosphine
-
The aqueous biphasic hydroformylation of 1-octene catalyzed by cobalt complex of the water-soluble ligand trisulfonated tris(biphenyl)phosphine (BiphTS) was investigated in the absence and presence of various mass transfer promoters (co-solvents, surfactants, cyclodextrins and activated carbon). In the presence of cetyltrimethylammonium bromide, methylated β-cyclodextrin or activated carbon, the Co/BiphTS system allowed the hydroformylation of 1-octene with high conversion (92-95%) and aldehydes selectivity (85-90%). Moreover, the catalytic system could be easily reused in the presence of activated carbon as a mass-transfer promoter. In all cases, the conversion and the aldehydes selectivity were found to depend strongly on the ligand/cobalt ratio.
- Dabbawala, Aasif A.,Bajaj, Hari C.,Bricout, Hervé,Monflier, Eric
-
scheme or table
p. 273 - 279
(2012/03/27)
-
- Hydroformylation of 1-octene using low-generation Rh(i) metallodendritic catalysts based on a tris-2-(2-pyridyliminoethyl)amine scaffold
-
The synthesis and characterization of low-generation pyridylimine Rh(i) metallodendrimers is described. These metallodendrimers were obtained via a Schiff base condensation of tris-2-(aminoethyl)amine with 2- pyridinecarboxaldehyde to afford the tris-2-(2-pyridylimine ethyl) amine ligand (1). Subsequent complexation reactions with [RhCl(CO)2]2 and [RhCl(COD)]2 yielded the corresponding metal-containing dendrimers containing -RhCl(CO) and -Rh(COD) moieties on the periphery. These new rhodium metallodendrimers (2 and 3) and their precursor ligand (1) are thermally stable and have been characterized using 1H NMR, 13C NMR, 31P NMR, FT-IR spectroscopy, elemental analysis as well as mass spectrometry. The Rh(i) metallodendrimers are highly active and chemo- and regioselective in the hydroformylation of 1-octene. Aldehydes were favoured at moderate to high temperatures (95 °C and 75 °C) and pressure (30 bars), while more iso-octenes were formed at low temperature (55 °C) and pressures (5 and 10 bars). The mononuclear analogues (5 and 6) also produced more aldehydes (albeit showing catalyst decomposition at 95 °C and 75 °C, 30 bars) and these aldehydes were mostly branched.
- Makhubela, Banothile C. E.,Jardine, Anwar M.,Westman, Gunnar,Smith, Gregory S.
-
p. 10715 - 10723
(2013/01/14)
-
- Synthesis of group 9 metal-olefin complexes with identical ligand frameworks and comparison of their catalytic activity in [2+2+2] cycloaddition and other addition reactions
-
The preparation and catalytic evaluation of the three group 9 (cyclopentadienyl)metal(trimethylvinylsilane) complexes of the type C 5H5M(H2C=CHSiMe3)2 (M=cobalt, rhodium and iridium) are reported. The complexes were investigated in [2+2+2] cycloaddition as well as in hydrogenation, hydroformylation and hydroboration reactions. Despite the identical organic frameworks and structural parameters, the complexes display remarkable reactivity and stability differences. Copyright
- Weding, Nico,Jackstell, Ralf,Jiao, Haijun,Spannenberg, Anke,Hapke, Marko
-
scheme or table
p. 3423 - 3433
(2012/03/09)
-
- Heterogenised N-heterocyclic carbene complexes: Synthesis, characterisation and application for hydroformylation and C-C bond formation reactions
-
The imidazolium salts: 1-mesityl-3-(3-trimethoxysilylpropyl)imidazolium iodide and 1-tert-butyl-3-(3-trimethoxysilylpropyl)imidazolium iodide, abbreviated as (tmpMes)HI (3a) and (tmptBu)HI (3b), respectively, have been synthesised. The palladium(ii) complexes (η3-C 3H5) (tmpMes)PdCl (5a) and (η3-C 3H5)(tmptBu)PdCl (5b), rhodium(i) and iridium(i) complexes (η4-1,5-COD) (tmpMes)MCl, M = Rh (6a), Ir (7a) and (η4-1,5-COD)(tmptBu)MCl, where M = Rh (6b), Ir (7b), were synthesised by silver transmetallation reactions using the silver(i) complexes (tmpMes)AgI (4a) and (tmptBu)AgI (4b). The iridium complex 7b has been structurally characterised. The Pd(ii) and Rh(i) complexes have been immobilised by attachment to chemically modified MCM-41. The immobilised palladium(ii) materials have been tested as recyclable catalysts for Suzuki type C-C bond formation reactions in water and the immobilised rhodium(i) materials have been examined for their catalytic ability for the hydroformylation of 1-octene.
- Dastgir, Sarim,Coleman, Karl S.,Green, Malcolm L. H.
-
experimental part
p. 661 - 672
(2011/02/28)
-
- Trianionic NCN3- pincer complexes of chromium in four oxidation states (CrII, CrIII, CrIV, CrV): Determination of the active catalyst in selective 1-alkene to 2-alkene isomerization
-
The synthesis and characterization of a series of four Cr complexes in the +2, +3, +4, and +5 oxidation states supported by an NCN trianionic pincer ligand are reported. Treating CrMeCl2(THF)3 with the dilithio salt pincer ligand precursor {[2,6-iPrNCHNLi2}2 provides the CrIII complex [2,6-iPrNCNCr III(THF)3 (1), CrIV complex [2,6- iPrNCNCrIVMe(THF) (2), and CrII complex [2,6-iPrNHCNCrII(THF)2 (3). Complexes 2 and 3 are the result of disproportionation. Treating 1 with 1 equiv of styrene oxide in THF converts the CrIII complex to the CrV(O) species [2,6-iPrNCNCrV(O)(THF) (4). Complex 2, characterized by single-crystal X-ray diffraction, is a rare CrIV methyl complex that is kinetically stable at 25 °C; at 85 °C, Cr-Me bond homolysis occurs. The homolytic cleavage results in CH4 formation and biphenyl via a radical mechanism. The metal-containing product from thermolysis is the same CrII species formed during metalation, except one of the protons is substituted for a deuterium from C6D6 (3-d). Complex 2 is a precatalyst for the selective isomerization of 1-hexene and 1-octene to the corresponding 2-alkenes. An induction period occurs during the catalytic isomerization, and the active catalyst was determined to be the CrII complex 3, not 2.
- McGowan, Kevin P.,Abboud, Khalil A.,Veige, Adam S.
-
experimental part
p. 4949 - 4957
(2011/11/05)
-
- Expanded ring N-heterocyclic carbene complexes of zero valent platinum dvtms (divinyltetramethyldisiloxane): Highly efficient hydrosilylation catalysts
-
The synthesis and characterisation of a series of new 6- and 7-membered NHC (N-heterocyclic carbene) complexes 7-12 of zero valent platinum dvtms (divinyltetramethyldisiloxane), [Pt(NHC)(dvtms)] are reported. A number of the complexes were investigated as catalyst precursors in the hydrosilylation of a range of unsaturated substrates, including alkynes, alkenes and a ketone with triethylsilane and bis(trimethylsiloxy)methylsilane (MD'M), at low catalyst loading (0.005 mol %); in general, the activity, and the selectivity for 1-functionalised product was found to be high.
- Dunsford, Jay J.,Cavell, Kingsley J.,Kariuki, Benson
-
experimental part
p. 188 - 194
(2011/02/16)
-