286-62-4Relevant articles and documents
Reaction of cyclooctenes with singlet oxygen. Trapping of a perepoxide intermediate
Poon, Thomas H. W.,Pringle, Kenneth,Foote, Christopher S.
, p. 7611 - 7618 (1995)
The products and rate constants for total physical and chemical quenching (kq + kr) of singlet oxygen (1O2) by cis- and trans-cyclooctene were determined in two solvents of different polarity. Small amounts of cis-cyclooctene are produced during the reaction of the trans-isomer. In CDCl3 and acetone-d6, kq + kr for cis-cyclooctene was 1.3 × 104 M-1 s-1 while the rate constants (kr) for the reaction of trans-cyclooctene were 2.3 × 104 and 3.4 × 104 M-1 s-1, respectively. Competition experiments with 2-methyl-2-pentene (2M2P) suggest a substantial contribution of physical quenching for the trans-alkene while the cis-alkene removes 1O2 mostly by chemical reaction. The physical quenching of 1O2 by trans-cyclooctene is explained by a perepoxide intermediate which can open to a zwitterion that can abstract an allylic hydrogen to give the 3-hydroperoxycyclooctene ene product or isomerize and lose O2 to form cis-cyclooctene. A perepoxide intermediate can be trapped using triphenyl phosphite with trans-but not cis-cyclooctene. trans-Cyclooctene quenches 3C70 with a rate constant of 3.4 × 105 M-1 s-1.
Synthesis of carbon quantum dots/SiO2 porous nanocomposites and their catalytic ability for photo-enhanced hydrocarbon selective oxidation
Han, Xiao,Han, Yuzhi,Huang, Hui,Zhang, Hengchao,Zhang, Xing,Liu, Ruihua,Liu, Yang,Kang, Zhenhui
, p. 10380 - 10383 (2013)
We report a facile hydrolytic process for the preparation of CQDs/SiO 2 porous nanocomposites, which show high catalytic activity and stability for the selective oxidation of cis-cyclooctene under visible light irradiation, with TBHP as a radical initiator and oxygen (in the air) as an oxidant at 80 °C.
A novel platform for modeling oxidative catalysis in non-heme iron oxygenases with unprecedented efficiency
Company, Anna,Goì?mez, Laura,Fontrodona, Xavier,Ribas, Xavi,Costas, Miquel
, p. 5727 - 5731 (2008)
A study was conducted to demonstrate a number of non-heme iron complexes, based on the methylpyridine derivatized triazacyclononane (TACN) backbone. It was found that these iron complexes show significant efficiency in the stereospecific oxidation of alkanes with H2O2, bypassing the latest oxidations catalyzed by TPA and BPMEN complexes. It was also demonstrated that the type of substitution on the N atoms of the triazamacrocyle and on the pyridine ring are key tools, to control the selectivity of the iron complexes in catalytic alkane and alkene oxidation reactions. It was also shown that this structural control of the catalytic selectivity in bioinspired oxidation reactions makes the iron complexes an efficient platform, to mimic iron dependent oxygenase reactivity.
Tantalum-Polyhedral Oligosilsesquioxane Complexes as Structural Models and Functional Catalysts for Epoxidation
Guillo, Pascal,Lipschutz, Michael I.,Fasulo, Meg E.,Tilley, T. Don
, p. 2303 - 2312 (2017)
Tantalum-based supported catalysts have been shown to be very selective for epoxidations with aqueous hydrogen peroxide. To gain information relative to the active site on the surface, access to molecular complexes that mimic the active site of the catalyst on the surface is of great interest. In this contribution, several new Ta-polyhedral oligosilsesquioxane (POSS) complexes with POSS ligands are used to model silica-bound Ta sites and are shown to be active as epoxidation catalysts. Notably, a Ta-POSS complex modified by germanoxy ligands and possessing a dinuclear Ta(μ-O)(μ-OH)Ta core is observed to be very efficient for the epoxidation of cyclooctene using aqueous hydrogen peroxide.
Fluorinated solvents in methyltrioxorhenium-catalyzed olefin epoxidations
Altmann, Philipp,Cokoja, Mirza,Kuehn, Fritz E.
, p. 3235 - 3239 (2012)
Epoxidations with methyltrioxorhenium(VII) (MTO) as catalyst precursor and additives are examined in fluorinated solvents under various conditions. These fluorinated solvents have a strong influence on the 1H NMR, 13C NMR, and 17O NMR spectroscopic data of the catalyst precursor, apparently contributing significantly to the catalytic activity of such systems. Accordingly, the highest turnover frequencies (TOF) obtained with MTO-containing systems have been determined, reaching up to 39000 h -1. Despite the high initial activity, such systems show a pronounced sensitivity to water leading also to faster catalyst decomposition. The high activity as well as the high sensitivity of the catalyst may be due to its solvent-enhanced higher Lewis acidity, leading to quantitative epoxide yields only when quite stable epoxides are the end products and very high amounts of Lewis base additives are applied.
Alkene Oxidation in Water using Hydrophobic Silica Particles Derivatized with Polyoxometalates as Catalysts
Neumann, Ronny,Miller, Hagit
, p. 2277 - 2278 (1995)
An insoluble catalytic assembly consisting of a silicate xerogel covalently modified with phenyl groups and quaternary ammonium-polyoxometalate ion pairs was used to catalyse the oxidation of alkenes with 30percent aqueous hydrogen peroxide in the absence of an organic solvent.
Ag3PW12O40/C3N4 nanocomposites as an efficient photocatalyst for hydrocarbon selective oxidation
Zhang, Yalin,Hu, Lulu,Zhao, Shunyan,Liu, Naiyun,Bai, Liang,Liu, Juan,Huang, Hui,Liu, Yang,Kang, Zhenhui
, p. 60394 - 60399 (2016)
Ag3PW12O40/C3N4 nanocomposites were successfully synthesized by loading Ag3PW12O40 into C3N4, in which case Ag3PW12O40
Dichloro and dimethyl dioxomolybdenum(VI)-diazabutadiene complexes as catalysts for the epoxidation of olefins
Valente, Anabela A.,Moreira, Jose,Lopes, Andre D.,Pillinger, Martyn,Nunes, Carla D.,Romao, Carlos C.,Kuehn, Fritz E.,Goncalves, Isabel S.
, p. 308 - 313 (2004)
The dioxomolybdenum(VI) complex [MoO2Cl2{p- tolyl(CH3DAB)}] has been prepared in good yield by reaction of the solvent adduct MoO2Cl2(THF)2 with one equivalent of the bidentate ligand N,N-p
Kinetic study of cyclooctene epoxidation with aqueous hydrogen peroxide over silica-supported calixarene-Ta(V)
Morlanes, Natalia,Notestein, Justin M.
, p. 45 - 54 (2010)
Replacing traditional TaCl5 precursors, calixarene-Ta(V) complexes are grafted on SiO2 at self-limiting loadings of 0.2 mmol·g-1 (0.25 Ta·nm-2) to synthesize an active and selective catalyst for epoxidation with aqueous H2O 2. The catalyst is synthesized in a one-pot procedure and has turnover rates that are a very weak function of Ta surface density, in contrast with catalysts that are subsequently calcined, following traditional practice. Cyclooctene epoxidation turnover rates exceed 240 h-1 and epoxide hydrolysis to the cyclooctanediol is extremely low, 2O2 decomposition is also decreased by 50% when using the calixarene capping ligand as compared to the bare oxide. A kinetic study of this system indicates a near first order dependence of the epoxidation rate on Ta content and H 2O2 concentrations; cyclooctene is weak positive order indicating some inhibition. H2O, product epoxide, and co-product cyclooctanediol are inhibitors, with cyclooctanediol being the strongest inhibitor on a molar basis, underscoring the importance of the reduced selectivity towards this species for the capped catalyst. A kinetic expression is proposed and describes initial rates and epoxide yields with time in good agreement with experimental data. The proposed catalytic cycle includes equilibrated formation of six-coordinate Ta(OH)X surface species as the most abundant intermediates. The rate limiting step is proposed to be the reaction between an activated Ta-hydroperoxide and an alkene in free solution, involving an external nucleophilic attack of the pi-system of the olefin on the relatively electropositive oxygen of the Ta-hydroperoxide species. The bulky and hydrophobic phenolate ligands pay a role in maintaining high Ta oxide dispersion, decreasing inhibition by polar species, and creating intrinsically more Lewis acidic sites, leading to increased epoxidation rates and decreased rates of undesired H2O2 decomposition and epoxide hydrolysis. This new class of ligand-capped, supported Ta oxide catalyst is not only more active and selective than its bare oxide analogue, but also provides a well-behaved catalyst for kinetic modeling.
Dioxotungsten(VI) complexes with isoniazid-related hydrazones as (pre)catalysts for olefin epoxidation: Solvent and ligand substituent effects
Vrdoljak, Vi?nja,Pisk, Jana,Prugove?ki, Biserka,Agustin, Dominique,Novak, Predrag,Matkovi?-?alogovi?, Dubravka
, p. 36384 - 36393 (2016)
The mononuclear dioxotungsten(vi) complexes [WO2(L3OMe)(D)] (1a and 1b), [WO2(L4OMe)(D)] (2a and 2b) and [WO2(LH)(D)] (3a and 3b) (D = EtOH (1a-3a) or MeOH (1b-3b); L3OMe = 3-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, L4OMe = 4-methoxy-2-oxybenzaldehyde isonicotinoyl hydrazonato, LH = 2-oxybenzaldehyde isonicotinoyl hydrazonato) were synthesized by the reaction of [WO2(acac)2]·0.5C6H5Me with the respective isoniazid-related hydrazone. The compounds were characterized by microanalysis, FT-IR and NMR spectroscopy, thermogravimetric analysis, and powder X-ray diffraction method. The crystal and molecular structures of 1a, 1b, 3a and [WO2(acac)2]·0.5C6H5Me were determined by single crystal X-ray diffraction. The structures of 1a, 1b, 3a are mononuclear and form hydrogen bonded centrosymmetric dimers. In all three complexes, the dimers are also held together by π?π interactions between aromatic rings. The catalytic performances (activity and selectivity) of 1a-3a and 1b-3b towards alkene epoxidation by tert-butyl hydroperoxide (TBHP) were investigated under different conditions.
Enhanced alkenes epoxidation reactivity of discrete bis(8-quinolinol) oxovanadium(IV) or bis(8-quinolinol)dioxomolybdenum(VI) tethered to graphene oxide by a metal-template/metal-exchange method
Li, Zhifang,Wu, Shujie,Zheng, Dafang,Liu, Heng,Hu, Jing,Su, Hailiang,Sun, Jian,Wang, Xu,Huo, Qisheng,Guan, Jingqi,Kan, Qiubin
, p. 104 - 114 (2014)
A series of imprinted catalysts were obtained by covalent attachment of discrete bis(8-quinolinol)oxovanadium(IV) or bis(8-quinolinol) dioxomolybdenum(VI) complex onto graphene oxide (GO) through the metal-template/metal-exchange method to control the distribution of covalently attached independent ligands, which were examined as catalysts in the epoxidation of alkenes using t-butylhydroperoxide (TBHP) or H2O 2 as oxidant in comparison with their homogeneous counterparts and materials synthesized by random grafting of the ligand. The prepared catalysts were characterized by XRD, N2 adsorption/desorption, TEM, FT-IR, diffusion reflection UV-visible, ICP-AES, TG, Raman, EPR, N element analysis and XPS. FT-IR, diffusion reflection UV-visible, ICP-AES, TG, N element analysis, Raman and XPS results showed that oxovanadium(IV) or dioxomolybdenum(VI) complexes were successfully grafted on GO. XRD, N2 adsorption/desorption and TEM results indicated that the structures of the samples were well preserved. EPR results revealed that the materials synthesized by the metal-template method had better site-isolation compared with conventional materials. Furthermore, these imprinted oxovanadium(IV) or dioxomolybdenum(VI) complex catalysts are efficient and recyclable, which exhibit higher activity and higher selectivity to target product than either their homogeneous ones or randomly grafted analogues due to better site-isolation.
Do (pentaarylcyclopentadienyl)molybdenum(vi) dioxo species catalyse alkene epoxidations? Insights from kinetics data
Pratt, Michael,Harper, Jason B.,Colbran, Stephen B.
, p. 2746 - 2748 (2007)
A (perarylcyclopentadienyl)molybdenum(vi) dioxo complex is shown to catalyse epoxidation of cyclooctene by t-butylhydroperoxide, but decomposition to a much more active non-cyclopentadienyl containing catalyst occurs as the reaction proceeds. The Royal So
Investigation of the reaction mechanism for the epoxidation of alkenes with hydrogen peroxide catalyzed by a protonated tetranuclear peroxotungstate with nmr spectroscopy, kinetics, and DFT calculations
Ishimoto, Ryo,Kamata, Keigo,Mizuno, Noritaka
, p. 1943 - 1950 (2013)
For the epoxidation of cyclooctene with hydrogen peroxide (H 2O2), the catalytic activity of a dinuclear peroxotungstate, [{WO(O2)2}2(μ-O)] 2-, is strongly dependent on additives, and HClO4 is the most effective. The reaction of [{WO(O2)2} 2(μ-O)]2- with HClO4 (0.5 equiv.) gives a protonated tetranuclear peroxotungstate, [H{W2O2(O 2)4(μ-O)}2]3- (I). The diastereoselectivity for epoxidation of 3-methyl-1-cyclohexene shows that steric constraints of the active site of I are comparable to those of di- and tetranuclear peroxotungstates with XO4n- ligands (X = SeVI, AsV, PV, SVI, and Si IV). The lowest XSO [XSO = (nucleophilic oxidation)/(total oxidation)] value of 0.13 for the I-catalyzed oxidation of thianthrene 5-oxide among peroxotungstates reveals that I has the most electrophilic active oxygen species. Kinetic and spectroscopic results show that an inactive species (I′) is reversibly formed by the reaction of I with water. Reaction rates for the catalytic epoxidation show first-order dependences on concentrations of alkene and I and a zero-order dependence on concentrations of H2O2. All these results indicate that oxygen transfer from I to a C=C double bond in an alkene is the rate-determining step. Computational studies support the proposed reaction mechanism. Copyright
Facile fabrication of magnetic MoO2–Salen-modified graphene-based catalyst for epoxidation of alkenes
Li, Zhifang,Yang, Changlong,Ma, Yuanyuan,Li, Peng,Guan, Jingqi,Kan, Qiubin
, (2017)
A facile, green and efficient method for the immobilization of MoO2–Salen onto graphene hybridized with glucose-coated magnetic Fe3O4 nanoparticles is proposed to fabricate a magnetic organic–inorganic hybrid heterogeneous RGO/Fe3O4@C-Salen-MoO2 catalyst for the epoxidation of cyclooctene and geraniol using tert-butyl hydroperoxide or H2O2 as oxidant. Carbon-coated Fe3O4 can improve the stability and add functional ─OH groups on the surface of Fe3O4. The fabricated composite exhibited good performance due to good dispersion of MoO2–Salen active sites. The catalyst can be easily separated from the reaction system using a permanent magnet and used three times without significantly losing its catalytic activity and selectivity.
Silica supported transition metal substituted polyoxotungstates: Novel heterogeneous catalysts in oxidative transformations with hydrogen peroxide
Estrada, Ana C.,Santos, Isabel C.M.S.,Sim?es, Mário M.Q.,Neves, M. Graa P.M.S.,Cavaleiro, José A.S.,Cavaleiro, Ana M.V.
, p. 28 - 35 (2011)
The preparation and characterization (FT-IR, FT-Raman, diffuse reflectance, elemental analysis) of novel catalysts with iron or manganese substituted polyoxotungstates [XMIII(H2O)W11O 39]n- (X = P, M = Fe or Mn; X = Si or B, M = Fe) immobilized on a functionalized silica matrix are reported. The new materials were tested as heterogeneous catalysts in the oxidation of cis-cyclooctene and cyclooctane at 80 °C, using environmentally safe hydrogen peroxide as oxidant and acetonitrile as solvent. Some of these novel heterogeneous catalysts could be reused several times without appreciable loss of catalytic activity.
Heterogenization of organometallic molybdenum complexes with siloxane functional groups and their catalytic application
Sakthivel, Ayyamperumal,Zhao, Jin,Hanzlik, Marianne,Chiang, Anthony S. T.,Herrmann, Wolfgang A.,Kuhn, Fritz E.
, p. 473 - 483 (2005)
η5-CpMo(CO)3R complexes containing siloxane functional groups [(CH2)3Si(OMe)3 or (CH 2) Si(OEt)3] attached to either the cyclopentadiene ligand or directly to Mo were grafted on the mesoporous materials MCM-41 and MCM-48 by reaction of the OR (R = Me, Et) moieties in the silane ligand and surface silanol groups (Si-OH). For the sake of comparison mesoporous materials modified with silane groups were reacted with Na+[CpMo(CO)3] -. The XRD, N2 adsorption-desorption, and TEM analyses provide strong evidence that the mesoporous structure of the supporting material retains its long-range ordering throughout the grafting process, despite significant reductions in surface area, pore volume and pore size. The appearance of strong IR bands around 2016 and 1956 cm-1 on the grafted samples also shows that the η5- InIi(II)3E complexes have been successfully grafted. Elemental analysis reveals that the grafted samples contain 0.3-3.5 wt % Mo. 29Si CP MAS-NMR spectra give clear evidence for a reduction in the numbers of the Q3 and Q2 sites. The formation of new peaks around -49.8, -57.9, and -66.2 ppm (T1, T2, and T3) indicates esterification of silanol groups by the alkoxy groups of the silane ligand. Both the in situ and ex situ prepared samples show good catalytic activity for the epoxidation of cyclooctene.
Simple Hybrids Based on Mo or W Oxides and Diamines: Structure Determination and Catalytic Properties
Bo?ek, Barbara,Neves, Patrícia,Oszajca, Marcin,Valente, Anabela A.,Po?towicz, Jan,Pamin, Katarzyna,?asocha, Wies?aw
, p. 713 - 727 (2020)
Abstract: Crystalline hybrid catalysts based on molybdenum or tungsten oxide and aliphatic diamines were synthesized via simple, eco-friendly reproducible methodologies, starting from commercially available and relatively inexpensive organic and inorganic
Hybrid peroxotungstophosphate organized catalysts highly active and selective in alkene epoxidation
Swalus, Colas,Farin, Benjamin,Gillard, Fran?ois,Devillers, Michel,Gaigneaux, Eric M.
, p. 80 - 84 (2013)
Heterogenization of homogeneous catalysts is still a challenge but can improve drastically the processability of these compounds. Hybridization of polyoxometalates offers an efficient heterogenization route of homogeneous epoxidation catalysts. The Keggin [PW12O40]3- and the Ventruello {PO4[WO(O2)2] 4}3- species were inserted by electrostatic interactions in a poly(ampholytic) polymeric matrix in order to prevent the leaching of these species. The presence of the polymeric matrix allows to tune the catalyst performance in cyclooctene epoxidation and to improve the selectivity to epoxide. Indeed, the hydrophobicity of the matrix induces a quick desorption of hydrophilic epoxide species. Their over-oxidation and the catalyst species deactivation by over-adsorption of epoxide are then avoided.
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Sheng
, p. 194 (1972)
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Transition-metal-free microporous and mesoporous catalysts for the epoxidation of cyclooctene with hydrogen peroxide
Pescarmona, Paolo P.,Van Noyen, Jasper,Jacobs, Pierre A.
, p. 307 - 314 (2007)
Transition-metal-free microporous and mesoporous materials were studied as heterogeneous epoxidation catalysts. MCM-41-type materials and zeolites with various porous structures and aluminium or gallium content but devoid of any transition metal were prepared and tested in the epoxidation of cyclooctene with aqueous hydrogen peroxide. The most promising catalytic results were obtained with Al-MCM-41, Ga-MCM-41, and ultra-stable zeolite Y (USY) with a low Si/Al ratio. All of these catalysts have acid sites of moderate strength. With Ga-MCM-41, 95% conversion of cyclooctene with 96% selectivity toward the epoxide was reached after 24 h of reaction. The catalyst could be recycled with no loss of catalytic properties.
Rhenium-containing compound(PyHReO4): synthesis, characterization and catalytic application in olefin epoxidation and baeyer-villiger oxidation
Dong, Yingnan,Li, Yucai,Song, Shiwei,Wang, Gang,Wang, Han,Wang, Jian,Wang, Shuaijie,Zhang, Dong,Zhao, Yan
, (2021/12/24)
A novel compound based on catalytic functional metal rhenium, pyridinium perrhenate(PyHReO4) was synthesized and characterized. The pyridinium perrhenate was used as catalyst in two types of reactions. One is the epoxidation of cyclooctene, the other is the Baeyer-Villiger oxidation of cyclic ketones to lactones. The effects of catalyst, oxidant, solvent, reaction time and temperature were investigated, which confirmed the optimum reaction conditions of the catalyst system. Both types of catalytic reactions exhibit high yields and high selectivity. Graphical abstract: The synthesized novel compound based on catalytic functional metal rhenium, pyridinium perrhenate(PyHReO4) exhibit excellent catalytic activity. The system with PyHReO4 as a catalyst provided an effective, easy separation, mild and convenient method in two different types of reactions(One is the epoxidation of cyclooctene, the other is the Baeyer-Villiger oxidation of 2-adamantanone). [Figure not available: see fulltext.]
Efficient and selective oxidation of hydrocarbons with tert-butyl hydroperoxide catalyzed by oxidovanadium(IV) unsymmetrical Schiff base complex supported on γ-Fe2O3 magnetic nanoparticles
Samani, Mahnaz,Ardakani, Mehdi Hatefi,Sabet, Mohammad
, p. 1481 - 1494 (2022/01/22)
The catalytic activity of an oxidovanadium(IV) unsymmetrical Schiff base complex supported on γ-Fe2O3 magnetic nanoparticles, γ-Fe2O3@[VO(salenac-OH)] in which salenac-OH = [9-(2′,4′-dihydroxyphenyl)-5,8-diaza-4
Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes
Ardakani, Mehdi Hatefi,Sabet, Mohammad,Samani, Mahnaz
, (2022/03/27)
In the present work, a dioxo-molybdenum unsymmetrical Schiff base complex, [MoO2(salenac-OH)], in which salenac-OH = [9-(2',4'-dihydroxyphenyl)-5,8-diaza-4-methylnona-2,4,8-trienato](-2), has been prepared and covalently immobilized on the sili
