14919-01-8Relevant academic research and scientific papers
Kinetics of the Sodium-Ammonia Reduction of 3-Octyne
Dewald, Robert R.,Ekstein, Cynthia J.,Song, Woo M.
, p. 6921 - 6922 (1987)
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.
Photocatalytic-controlled olefin isomerization over WO3–x using low-energy photons up to 625 nm
Sun, Xichen,Waclawik, Eric R.,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
, p. 1641 - 1647 (2021/06/28)
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.
The role of CO2 in the dehydrogenation of n-octane using Cr-Fe catalysts supported on MgAl2O4
Adam, Dailami S.,Bala, Muhammad D.,Friedrich, Holger B.,Mahomed, Abdul S.
, (2021/08/09)
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.
Ni-Catalyzed Isomerization-Hydrocyanation Tandem Reactions: Access to Linear Nitriles from Aliphatic Internal Olefins
Gao, Jihui,Ni, Jie,Yu, Rongrong,Cheng, Gui-Juan,Fang, Xianjie
supporting information, p. 486 - 490 (2021/02/05)
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.
Continuous flow hydrogenation with Pd complexes of pyridine-benzotriazole ligands
Y?lmaz, Filiz,Hür, Deniz
, (2021/08/03)
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.
ALCOHOL DEHYDRATION CATALYST, PREPARATION METHOD THE SAME AND METHOD FOR PREPARING ALPHA-OLEFINS USING THE SAME
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Paragraph 0030; 0132; 0133, (2020/11/24)
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.
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
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)
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.
Regioselective Isomerization of Terminal Alkenes Catalyzed by a PC(sp3)Pincer Complex with a Hemilabile Pendant Arm
De-Botton, Sophie,Filippov, D.Sc. Oleg A.,Shubina, Elena S.,Belkova, Natalia V.,Gelman, Dmitri
, p. 5959 - 5965 (2020/10/15)
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.
Graphdiyne-based Pd single-Atom catalyst for semihydrogenation of alkynes to alkenes with high selectivity and conversion under mild conditions
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)
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
Gem-Dialkyl Effect in Diphosphine Ligands: Synthesis, Coordination Behavior, and Application in Pd-Catalyzed Hydroformylation
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)
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.
