- Reaction of cyclooctenes with singlet oxygen. Trapping of a perepoxide intermediate
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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.
- Poon, Thomas H. W.,Pringle, Kenneth,Foote, Christopher S.
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- Alkene epoxidation catalyzed by manganese complexes with electronically modified 1,10-phenanthroline ligands
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The syntheses and alkene epoxidation activities of four manganese(II) complexes with electronically modified 1,10-phenanthroline ligands are reported. Each phenanthroline has a different substituent in the 5-position; the placement ensures that the modifications influence the reactivity through largely electronic effects. All four manganese complexes catalyze the conversion of alkenes to epoxides by commercially available peracetic acid. With each of the four alkenes investigated, the yield of the epoxide product is greater when the 5-substituent on the catalyst is strongly electron-donating, contrary to what has been observed with reactions catalyzed by manganese-salen complexes.
- Goldsmith, Christian R.,Jiang, Wenchan
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- Synthesis of carbon quantum dots/SiO2 porous nanocomposites and their catalytic ability for photo-enhanced hydrocarbon selective oxidation
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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.
- Han, Xiao,Han, Yuzhi,Huang, Hui,Zhang, Hengchao,Zhang, Xing,Liu, Ruihua,Liu, Yang,Kang, Zhenhui
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- A nitrate bridged one-dimensional copper(II) coordination polymer with a tridentate (NNO) Schiff base: synthesis, X-ray structure and catalytic efficacy
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A one-dimensional Cu(II) coordination polymer of [Cu(L)(μ-ONO2)]n (1) (HL = 4-methoxy-2-[1-(methylaminoethylimino)methyl]-phenol) with bidentate bridging nitrate has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. Single crystal?X-ray analysis revealed that each copper(II) center in the asymmetric unit of complex 1 adopts a distorted square pyramidal geometry with a CuN2O3 chromophore ligated through a tridentate Schiff base (L) with (NNO) donor sets and two O atoms of bridging nitrate ion. The adjacent copper atoms are connected by bridging nitrate (μ-ONO2) in bidentate fashion affording a 1D coordination polymeric chain structure along the?crystallographic b-axis. In the polymeric framework, the Cu…Cu separation is 4.3749(4) ?. The catalytic efficacy of complex 1 was studied in a series of solvents for the epoxidation of cyclooctene using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions. The catalytic reaction mixture was analyzed by gas chromatography and the data indicated that the yield of the epoxidation?reaction and its selectivity is maximum in acetonitrile medium.
- Chowdhury, Habibar,Bera, Rajesh,Rizzoli, Corrado,Adhikary, Chandan
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- A novel platform for modeling oxidative catalysis in non-heme iron oxygenases with unprecedented efficiency
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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.
- Company, Anna,Goì?mez, Laura,Fontrodona, Xavier,Ribas, Xavi,Costas, Miquel
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- Amphiphilic Mesoporous Poly(Ionic Liquid) Immobilized Heteropolyanions Towards the Efficient Heterogeneous Epoxidation of Alkenes with Stoichiometric Hydrogen Peroxide
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New mesoporous poly(ionic liquid)s (MPILs) that feature a pure polycationic framework and tunable hydrophobicity were synthesized through the free-radical polymerization of alkyl-functionalized ionic liquids (ILs) and bisvinylimidazolium salt. Phosphotung
- Shi, Yuming,Guo, Zengjing,Wang, Qian,Zhang, Lingyu,Li, Jing,Zhou, Yu,Wang, Jun
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- Tantalum-Polyhedral Oligosilsesquioxane Complexes as Structural Models and Functional Catalysts for Epoxidation
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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.
- Guillo, Pascal,Lipschutz, Michael I.,Fasulo, Meg E.,Tilley, T. Don
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- Microwave assisted one pot synthesis and characterization of Cesium salt of di-copper substituted phosphotungstate and its application in the selective epoxidation of cis-cyclooctene with tert-butyl hydroperoxide
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In the present work, we have isolated di-copper substituted phosphotungstate, Cs7[PW10Cu2(H2O)2O38]·9H2O, as a single isomer using novel microwave technique from the commercially
- Patel, Anjali,Sadasivan, Rajesh
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- Fluorinated solvents in methyltrioxorhenium-catalyzed olefin epoxidations
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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.
- Altmann, Philipp,Cokoja, Mirza,Kuehn, Fritz E.
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- Alkene epoxidation catalysed by ligand-bound supported metalloporphyrins
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Iron(III) and manganese(III) tetra(2,6-dichlorophenyl)porphyrin bound to surface imidazole and pyridine groups on solid supports are efficient catalysts for the expoxidation of cyclooctene by iodosylbenzene.
- Cooke, Paul R.,Lindsay Smith, John R.
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- Alkene Oxidation in Water using Hydrophobic Silica Particles Derivatized with Polyoxometalates as Catalysts
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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.
- Neumann, Ronny,Miller, Hagit
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- Molybdenum versus tungsten for the epoxidation of cyclooctene catalyzed by [Cp*2M2O5]
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The catalytic activity of [Cp*2M2O5] (M = Mo, W; Cp* = pentamethylcyclopentadienyl) for the homogeneous epoxidation of a solution of cyclooctene in MeCN/toluene follows the order Mo >> W when using tert-butyl hydroperoxide (TBHP)/decane as oxidant, in contrast to the inverse order (W >> Mo) when using aqueous H 2O2 as oxidant. The catalytic activity for the Mo system strongly depends on the solvent used to deliver the oxidant (TBHP/decane >> TBHP/H2O). The low activity of the W system is also decreased when using TBHP/water in place of TBHP/decane. For both metals, H 2O2/H2O is a better oxidant than TBHP/H 2O. However, whereas the Mo-based catalyst is much more active for the TBHP/decane epoxidation in spite of the lower TBHP oxidizing power (TBHP/decane > H2O2/H2O > TBHP/H 2O), the W-based system is much more active for the H 2O2/H2O epoxidation in spite of the negative effect of water (H2O2/H2O > TBHP/decane > TBHP/H2O). The kinetic profile of the TBHP/decane epoxidation process is affected by product inhibition. Initial rate measurements show that the rate law is first order with respect to substrate and has saturation behavior with respect to the oxidant. Copyright
- Soezen-Aktas, Pelin,Manoury, Eric,Demirhan, Funda,Poli, Rinaldo
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- Ag3PW12O40/C3N4 nanocomposites as an efficient photocatalyst for hydrocarbon selective oxidation
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Ag3PW12O40/C3N4 nanocomposites were successfully synthesized by loading Ag3PW12O40 into C3N4, in which case Ag3PW12O40
- Zhang, Yalin,Hu, Lulu,Zhao, Shunyan,Liu, Naiyun,Bai, Liang,Liu, Juan,Huang, Hui,Liu, Yang,Kang, Zhenhui
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- Oxidovanadium complexes with tetradentate Schiff bases: Synthesis, structural, electrochemical and catalytic studies
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A series of new tridentate Schiff base ligands derived from the condensation of 4,5-dinitro-1,2-phenylenediamine and various salicylaldehyde derivatives was synthesized and characterized by common spectroscopic and analytical methods. Oxidovanadium(IV) complexes of tetradentate Schiff base ligands derived from the condensation of this diamine and salicylaldehyde derivatives were also synthesized by template method and were characterized. The crystal structures of a tridentate ligand, HL2, and one of the complexes, VOLig2, were determined by X-ray crystallography. HL 2 crystallizes in triclinic space group P1?, while the VOLig2 (which crystallizes as the DMF solvate) in monoclinic space group P21/n with two [VOLig2] DMF symmetry-independent units per asymmetric part of the unit cell. The electrochemical properties of these complexes were studied by cyclic voltammetry which shows quasi-reversible VIV/VV redox process. The new complexes are also used as catalysts for the selective oxidation of cyclooctene with tert- butylhydroperoxide (TBHP) and H2O2 in acetonitrile. High catalytic activities were observed and excellent selectivity was found for the epoxidation of cyclooctene.
- Rahchamani, Jalal,Behzad, Mahdi,Bezaatpour, Abolfazl,Jahed, Vahdat,Dutkiewicz, Grzegorz,Kubicki, MacIej,Salehi, Mehdi
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- Dichloro and dimethyl dioxomolybdenum(VI)-diazabutadiene complexes as catalysts for the epoxidation of olefins
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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
- Valente, Anabela A.,Moreira, Jose,Lopes, Andre D.,Pillinger, Martyn,Nunes, Carla D.,Romao, Carlos C.,Kuehn, Fritz E.,Goncalves, Isabel S.
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- Dioxomolybdenum(VI)-Modified Mesoporous MCM-41 and MCM-48 Materials for the Catalytic Epoxidation of Olefins
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The dioxomolybdenum(VI) complex [MoO2Cl2(L-L)], containing the bidentate 1,4-diazabutadiene ligand RN= C(Ph)-C(Ph)=NR [R = (CH2)3Si(OEt)3], was immobilised in the ordered mesoporous silica MCM-41 by carrying out a grafting reaction in dichloromethane. The grafted material (3.3 wt.-% Mo) was tested as a catalyst for the epoxidation of cyclooctene with tert-butyl hydroperoxide (TBHP) at 55 °C. Selectivity to the epoxide was very high and the observed kinetic profile was similar to that of the complex [MoO2Cl2(L-L)] in the homogeneous phase. On recycling several times, some activity was lost from the first to second runs, but thereafter stabilised. Tethered complexes of this type were also prepared by a stepwise approach. The mesoporous silicas MCM-41 and MCM-48 were first treated with a toluene solution of the ligand L-L under reflux. Before isolating the grafted materials, the silylating agent Me3SiCl was added to remove the residual Si-OH groups on the surface of the mesoporous materials. Oxomolybdenum species were subsequently introduced into the ligand-silicas by pore volume impregnation of a solution of the complex [MoO2Cl2(THF)2] in CH 2Cl2 at room temperature. The modified materials have been characterised by powder X-ray diffraction, N2 adsorption, and solid-state MAS NMR (13C, 29Si). Despite having lower metal loadings (1 wt.-% Mo), the materials exhibited similar catalytic activities for the epoxidation of cyclooctene to that of the modified MCM-41 with 3.3 wt.-% of Mo. However, selectivities to the epoxide were lower. The MCM supported catalysts have also been tested for the epoxidation of cyclododecene and α-pinene with TBHP. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
- Nunes, Carla D.,Pillinger, Martyn,Valente, Anabela A.,Rocha, Joao,Lopes, Andre D.,Goncalves, Isabel S.
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- Kinetic study of cyclooctene epoxidation with aqueous hydrogen peroxide over silica-supported calixarene-Ta(V)
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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.
- Morlanes, Natalia,Notestein, Justin M.
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- REACTION OF SINGLET OXYGEN WITH TRANS-CYCLOOCTENE.EVIDENCE FOR A 1,2-DIOXETANE INTERMEDIATE.
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Evidence is presented that the reaction of 1O2 with trans-cyclooctene yields an unstable trans-fused bicyclic dioxetane as a significant product.
- Inoue, Y.,Turro, N.J.
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- Dioxotungsten(VI) complexes with isoniazid-related hydrazones as (pre)catalysts for olefin epoxidation: Solvent and ligand substituent effects
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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.
- Vrdoljak, Vi?nja,Pisk, Jana,Prugove?ki, Biserka,Agustin, Dominique,Novak, Predrag,Matkovi?-?alogovi?, Dubravka
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- MTO Schiff-base complexes: Synthesis, structures and catalytic applications in olefin epoxidation
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Several Schiff-base ligands readily form complexes with methyltrioxorhenium(VII) (MTO) by undergoing a hydrogen transfer from a ligand-bound OH group to a ligand N atom. The resulting complexes are stable at room temperature and can be handled and stored in air without problems. Due to the steric demands of the ligands they display distorted trigonal-bipyramidal structures in the solid state, as shown by X-ray crystallogra phy. with the O- moiety binding to the Lewis acidic Re atom and the Rebound methyl group being located either in cis or trans position to the Schiff base. In solution, however, the steric differences seem not to be maintained, as can be deduced from 17O NMR spectroscopy. Furthermore, the Schiff-base ligands exchange with donor ligands. Nevertheless, the catalytic behaviour is influenced significantly by the Schiff bases coordinated to the MTO moiety, which lead either to high selectivities and good activities or to catalyst decomposition. A large excess of ligand, in contrast to the observations with aromatic N-donor ligands, is detrimental to the catalytic performance as it leads to catalyst decomposition.
- Zhou, Ming-Dong,Zhao, Jin,Li, Jun,Yue, Shuang,Bao, Chang-Nian,Mink, Janos,Zang, Shu-Liang,Kuehn, Fritz E.
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- 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
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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.
- Li, Zhifang,Wu, Shujie,Zheng, Dafang,Liu, Heng,Hu, Jing,Su, Hailiang,Sun, Jian,Wang, Xu,Huo, Qisheng,Guan, Jingqi,Kan, Qiubin
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- High frequency ultrasound as a tool for elucidating mechanistic elements of cis-cyclooctene epoxidation with aqueous hydrogen peroxide
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The use of high frequency ultrasound (800 kHz) highlights the non-radical character of the cis-cyclooctene epoxidation mediated by H2O2 and H2WO4. Combination of moderate mixing brought by the ultrasonic irradiation with precise thermoregulation of the double jacketed sonoreactor demonstrates the potential of this technique for studying and optimizing all the reaction parameters. The results not only reveal that the optimized ultrasonic conditions lead to excellent epoxidation outcomes with 96% yield and 98% selectivity but also to higher selectivities toward the epoxidation product compared with silent conditions.
- Cousin, Tony,Chatel, Gregory,Kardos, Nathalie,Andrioletti, Bruno,Draye, Micheline
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- Do (pentaarylcyclopentadienyl)molybdenum(vi) dioxo species catalyse alkene epoxidations? Insights from kinetics data
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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
- Pratt, Michael,Harper, Jason B.,Colbran, Stephen B.
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- SiO2-surface-assisted controllable synthesis of TaON and Ta 3N5 nanoparticles for alkene epoxidation
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Touching the surface: Well-defined TaON and Ta3N5 nanoparticles were fabricated by a SiO2-surface-assisted urea method, in which silica catalyzes CNx formation from urea. Such controlled nitridation endows the nanoparticles with improved activity and tunable selectivity for alkene epoxidation because of the increased electron density around Ta and surface basicity. Copyright
- Gao, Qingsheng,Wang, Sinong,Ma, Yuchun,Tang, Yi,Giordano, Cristina,Antonietti, Markus
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- 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
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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
- Ishimoto, Ryo,Kamata, Keigo,Mizuno, Noritaka
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- N-heterocyclic carbene-based molybdenum and tungsten complexes as efficient epoxidation catalysts with H2O2 and tert-butyl hydroperoxide
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The molybdenum and tungsten η3-allyl dicarbonyl complexes bearing N-heterocyclic carbene (NHC) ligands [M(η3-C 3H5)Cl(CO)2(bis-NHCBz)] (M = Mo, W; bis-NHCBz = 1,1'-dibenzyl-3,3'-
- Krishna Mohan Kandepi,Cardoso, Joao M. S.,Royo, Beatriz
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- Facile fabrication of magnetic MoO2–Salen-modified graphene-based catalyst for epoxidation of alkenes
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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.
- Li, Zhifang,Yang, Changlong,Ma, Yuanyuan,Li, Peng,Guan, Jingqi,Kan, Qiubin
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- X-Ray crystal structure of (tetraphenylimidodiphosphinato)silver(I): An unexpected tetranuclear complex with two modes of coordination of silver
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Potassium tetraphenylimidodiphosphinate reacts with silver nitrate to give, upon recrystallization from ethanol, an unexpected tetranuclear complex [Ag{N(OPPh2)2}]4·2EtOH, the structure of which is established by X-ray cry
- Rudler, Henri,Denise, Bernard,Gregorio, Jose Ribeiro,Vaissermann, Jacqueline
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- Silica supported transition metal substituted polyoxotungstates: Novel heterogeneous catalysts in oxidative transformations with hydrogen peroxide
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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.
- 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.
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- Multiple bonds between transition metals and main-group elements part 168. 1 methyltrioxorhenium/Lewisbase catalysts in olefin epoxidation
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Methyltrioxorhenium(VII) (MTO) forms with H2O2 and Lewis bases, e.g., pyridine, a powerful, highly selective oxidant for olefins, both under mono-phase (alcohols as solvents) and biphasic conditions (CH2Cl2/H2O). Large excess of pyridine is required to maintain the catalytic activity due to rapid oxidation of pyridine to pyridine N-oxide, which reaction is catalyzed by MTO, too. The selectivity to epoxides, however, remains high throughout the course of the catalysis, since pyridine N-oxide also forms a highly selective but much less active co-catalyst with MTO/H2O2. Under two-phase conditions, the presence of the aqueous phase ensures high epoxidation activities due to rapid, efficient removal of the pyridine N-oxide.
- Herrmann, Wolfgang A.,Ding, Hao,Kratzer, Roland M.,Kuehn, Fritz E.,Haider, Joachim J.,Fischer, Richard W.
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- Heterogenization of organometallic molybdenum complexes with siloxane functional groups and their catalytic application
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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.
- Sakthivel, Ayyamperumal,Zhao, Jin,Hanzlik, Marianne,Chiang, Anthony S. T.,Herrmann, Wolfgang A.,Kuhn, Fritz E.
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- Conflicting Role of Water in the Activation of H2O2 and the Formation and Reactivity of Non-Heme FeIII-OOH and FeIII-O-FeIII Complexes at Room Temperature
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The formation of an FeIII-OOH species by reaction of complex 1 ([(MeN3Py)FeII(CH3CN)2]2+) with H2O2 at room temperature is reported and is studied by a combination of UV/vis absorption, EPR, and resonance Raman spectroscopies. The formation of the FeIII-OOH species, and its subsequent conversion to relatively inert FeIII-O-FeIII species, is shown to be highly dependent on the concentration of water, with excess water favoring the formation of the latter species, which is studied by UV/vis absorption spectroelectrochemistry also. The presence of acetic acid increases the rate and extent of oxidation of 1 to its iron(III) state and inhibits the wasteful decomposition of H2O2 but does not affect significantly the spectroscopic properties of the FeIII-OOH species formed.
- Padamati, Sandeep K.,Draksharapu, Apparao,Unjaroen, Duenpen,Browne, Wesley R.
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- Simple Hybrids Based on Mo or W Oxides and Diamines: Structure Determination and Catalytic Properties
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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
- Bo?ek, Barbara,Neves, Patrícia,Oszajca, Marcin,Valente, Anabela A.,Po?towicz, Jan,Pamin, Katarzyna,?asocha, Wies?aw
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- Ansa-bridged η5-cyclopentadienyl molybdenum and tungsten complexes: Synthesis, structure and application in olefin epoxidation
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Ansa-bridged η5-cyclopentadienyl molybdenum and tungsten tricarbonyl complexes of formula [M(η5-C5H 4(CH2)3-η1-CH 2)(CO)3] (M = Mo or W) were synthesized an
- Zhao, Jin,Jain, Kavita R.,Herdtweck, Eberhardt,Kuehn, Fritz E.
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- Hybrid peroxotungstophosphate organized catalysts highly active and selective in alkene epoxidation
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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.
- Swalus, Colas,Farin, Benjamin,Gillard, Fran?ois,Devillers, Michel,Gaigneaux, Eric M.
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- Performance of a tetracarbonylmolybdenum(0) pyrazolylpyridine (pre)catalyst in olefin epoxidation and epoxide alcoholysis
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Tetracarbonylmolybdenum(0) complexes of the type cis-[Mo(CO)4(L)] are attractive synthetic precursors of high oxidation state oxomolybdenum catalysts since the byproducts (CO/CO2) readily separate from the reaction mixture, facilitating separation/purification procedures (e.g. avoiding contamination/acidification of the medium for halide (X)-containing precursors such as [Mo(η3-C3H5)Cl(CO)2(L)]). In this work, the conversion of the tetracarbonyl complex cis-[Mo(CO)4(ppp)] (ppp = 2-(1-pentyl-3-pyrazolyl)pyridine) to oxomolybdenum compounds has been studied. The molybdenum compounds prepared were explored for liquid phase oxidation and acid catalysis, specifically the epoxidation of cis-cyclooctene with hydroperoxide oxidants, and the alcoholysis of styrene oxide. The routes for the conversion of the cis-[Mo(CO)4(ppp)] precursor to oxomolybdenum compounds, during either the synthesis (ex situ) or catalytic (in situ) processes (involving isolation/characterisation of metal species after the catalytic runs), were studied for the different catalytic systems, which helped establish relationships between the type of metal species formed and the catalytic performance. Catalyst recyclability was investigated using a homogeneous catalytic ionic liquid-standing approach.
- Nogueira, Lucie S.,Neves, Patrícia,Gomes, Ana C.,Valente, Anabela A.,Pillinger, Martyn,Gon?alves, Isabel S.
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- Oxidorhenium(V) complexes with phenolate- and carboxylate-based ligands: Structure and catalytic epoxidation
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Several oxidorhenium(V) complexes with phenolate- and carboxylate-based ligands were synthesized: [ReOCl(hpbi)2]·THF, [ReOCl(hmpbta)2], [ReOBr(hmpbta)2], [ReOCl(hpbo) 2], [ReOCl(hpbt)2]·2MeCN, [ReO(OMe)(quin) 2], [ReO(OMe)(pic)2], [ReO(OMe)(2,5-dipic) 2]·C5H5N, [ReOCl(pic)2], and [ReOCl(3-ind)2] [in which Hhpbi = 2-(2-hydroxyphenyl)-1H- benzimidazole, Hhmpbta = 2-(2-hydroxy-5-methylphenyl)benzotriazole, Hhpbo = 2-(2-hydroxyphenyl)-2-benzoxazole, Hhpbt = 2-(2-hydroxyphenyl)benzothiazole, Hquin = quinaldic acid, picH = picolinic acid, 2,5-dipicH = 2,5- pyridinedicarboxylic acid, and 3-indH = indazole-3-carboxylic acid]. The compounds were characterized by spectroscopic methods and single-crystal X-ray diffraction analysis. Interestingly, the complex [ReO(OMe)(quin)2] is a rare trans-N,N and trans-O,O isomer of [ReOX(N-O)2] with two chelating quinoline-2-carboxylate ligands in the equatorial plane and a linear axial [O=Re-OMe] unit. The other disubstituted compounds were found to be the most common cis-N,N structure of [ReOX(N-O)2] with the oxygen atom of one of the chelating ligands in a trans position to the oxido ligand. All the complexes were tested in the epoxidation of cyclooctene with tert-butyl hydroperoxide (3 equiv.). The lowest conversion of only 3 % has been confirmed for [ReOCl(hpbi)2]. All other complexes reached yields of cyclooctane oxide between 58 and 75 %. Several oxidorhenium(V) complexes that contain phenolate- and carboxylate-based ligands were synthesized and characterized by spectroscopic means and by X-ray crystal structure analysis. The complexes are air- and moisture-stable and show catalytic activity for the epoxidation of cyclooctene. Copyright
- MacHura, Barbara,Wolff, Mariusz,Tabak, Dominik,Schachner, Joerg A.,Moesch-Zanetti, Nadia C.
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- Transition-metal-free microporous and mesoporous catalysts for the epoxidation of cyclooctene with hydrogen peroxide
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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.
- Pescarmona, Paolo P.,Van Noyen, Jasper,Jacobs, Pierre A.
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- Effect of pore sizes on catalytic activities of arenetricarbonyl metal complexes constructed within Zr-based MOFs
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Arenetricarbonyl metal complexes ([-phM(CO)3-] and [-biphM(CO)3-]; ph = phenylene, biph = biphenylene, M = Mo, Cr) constructed within Zr-based MOFs act as highly active and selective catalysts for epoxidation of cyclooctene. Catalyti
- Saito, Masakazu,Toyao, Takashi,Ueda, Kozo,Kamegawa, Takashi,Horiuchi, Yu,Matsuoka, Masaya
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- Rhenium-containing compound(PyHReO4): synthesis, characterization and catalytic application in olefin epoxidation and baeyer-villiger oxidation
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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.]
- Dong, Yingnan,Li, Yucai,Song, Shiwei,Wang, Gang,Wang, Han,Wang, Jian,Wang, Shuaijie,Zhang, Dong,Zhao, Yan
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- Green solvent free epoxidation of olefins by a heterogenised hydrazone-dioxidotungsten(vi) coordination compound
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A new mononuclear tungsten coordination compound, [WO2L(CH3OH)] (1), was synthesized by the reaction of WCl6 and H2L (H2L = (E)-4-amino-N′-(5-bromo-2-hydroxybenzylidene)benzohydrazide) in methanol. Bo
- Bikas, Rahman,Heydari, Neda,Lis, Tadeusz,Shaterian, Maryam
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p. 4813 - 4827
(2022/02/19)
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- Efficient and selective oxidation of hydrocarbons with tert-butyl hydroperoxide catalyzed by oxidovanadium(IV) unsymmetrical Schiff base complex supported on γ-Fe2O3 magnetic nanoparticles
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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
- Samani, Mahnaz,Ardakani, Mehdi Hatefi,Sabet, Mohammad
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p. 1481 - 1494
(2022/01/22)
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- MCM-41 supported heterogeneous catalyst for the conversion of alkene to epoxide: Synthesis, characterization and catalytic studies
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A new hybrid catalyst has been prepared by the immobilization of copper(II) α-diimine complex on the surface of mesoporous silica, MCM-41. The symmetrical α-diimine ligand has been prepared from dimethyl glyoxal and p-amino benzoic acid (PABA). The catalyst has been characterized by different analytical techniques such as elemental analysis, FT-IR, N2 sorption, small angle X-ray diffraction, thermogravimetric analysis (TGA), SEM and TEM. The PXRD and TEM measurements showed that the heterogeneous catalyst has mesoporosity. The catalyst has been tested in the conversion of alkene into epoxide using tert-butyl-hydroperoxide (tert-BuOOH) as oxidant in acetonitrile medium. The maximum yield (100%) was obtained with trans stilbene. The compared catalytic studies demonstrated that this catalyst is more effective in terms of reactivity and stability than its counter parts. This can be recycled and reused several times without significant loss of activity.
- Sharma, Saurabh,Singh, Udai P.
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- Dioxo-molybdenum(VI) unsymmetrical Schiff base complex supported on CoFe2O4@SiO2 nanoparticles as a new magnetically recoverable nanocatalyst for selective epoxidation of alkenes
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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
- Ardakani, Mehdi Hatefi,Sabet, Mohammad,Samani, Mahnaz
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- Catalytic oxygen atom transfer promoted by tethered Mo(VI) dioxido complexes onto silica-coated magnetic nanoparticles
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The preparation of three novel active and stable magnetic nanocatalysts for the selective liquid-phase oxidation of several olefins, has been reported. The heterogeneous systems are based on the coordination of cis-MoO2 moiety onto three different SCMNP@Si-(L1-L3) magnetically active supports, functionalized with silylated acylpyrazolonate ligands L1, L2 and L3. Nanocatalysts thoroughly characterized by ATR-IR spectroscopy, TGA and ICP-MS analyses, showed excellent catalytic performances in the oxidation of conjugated or unconjugated olefins either in organic or in aqueous solvents. The good magnetic properties of these catalytic systems allow their easy recyclability, from the reaction mixture, and reuse over five runs without significant decrease in the activity, either in organic or water solvent, demonstrating their versatility and robustness.
- Colaiezzi, Roberta,Crucianelli, Marcello,Di Giuseppe, Andrea,Ferella, Francesco,Lazzarini, Andrea,Paolucci, Valentina
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- Self-assembly of polyoxometalate clusters into two-dimensional clusterphene structures featuring hexagonal pores
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Two-dimensional (2D) structures have been shown to possess interesting and potentially useful properties. Because of their isotropic structure, however, clusters tend to assemble into 3D architectures. Here we report the assembly of polyoxometalate clusters into layered structures that feature uniform hexagonal pores and in-plane electron delocalization properties. Because these structures are 2D and visually reminiscent of graphene, they are referred to as ‘clusterphenes’. A series of multilayer and monolayer clusterphenes have been constructed with 13 types of polyoxometalate cluster. The resulting clusterphenes were shown to exhibit substantially improved stability and catalytic efficiency towards olefin epoxidation reactions, with a turnover frequency of 4.16 h?1, which is 76.5 times that of the unassembled clusters. The catalytic activity of the clusterphenes derives from the electron delocalization between identical clusters within the 2D layer, which efficiently reduces the activation energy of the catalytic reaction. [Figure not available: see fulltext.]
- Hu, Hanshi,Liu, Qingda,Shi, Wenxiong,Wang, Xun,Zhang, Qinghua,Zhuang, Jing
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p. 433 - 440
(2022/02/17)
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- Efficient and region-selective conversion of octanes to epoxides under ambient conditions: Performance of tri-copper catalyst, [Cu3I(L)]+1 (L=7-N-Etppz)
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In this paper, is described the conversion of the octane group of hydrocarbons into industrially important epoxides using tri-copper catalyst, [Cu3I(L)]+1 (L=7-N-Etppz). The role of hydrogen peroxide as a sacrificial oxygen donor during catalytic conversion to epoxides has been investigated. The performance of the catalyst has been evaluated in terms of turnover numbers (TON) and turnover frequencies (TOF) reported in this article.
- Krupadam, Reddithota J.,Nagababu, Penumaka,Paul, Perala Sudheer,Reddy, Thatiparthi Byragi
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p. 742 - 745
(2021/09/28)
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- Co(II) Schiff base Complexes Encapsulated in the Nanopores of Zeolite Y as Heterogeneous Catalysts for Selective Epoxidation of Alkenes with Molecular Oxygen
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Abstract: Co(II) macrocyclic Schiff base complex nanoparticles have been encapsulated in the nanopores of zeolite Y. The new Schiff base complexes entrapped in the nanoreactor of zeolite Y were characterized by several techniques: chemical analysis and spectroscopic methods (FT-IR, XRD, and DRS). These complexes (neat and encapsulated) were used for epoxidation of alkenes with O2 as oxidant in different solvents. The catalyst demonstrated excellent activity for a variety of alkenes in a mild, inexpensive and efficient protocol. Reaction parameters including temperature, catalyst amount and solvent were screened by reaction time. The recycling experiment results indicated that the catalysts were highly stable and maintained activity and selectivity even after being used for five cycles.
- Banaei, A. R.,Pourali, A. R.,Rezazadeh, B.,Tabari, S.
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p. 424 - 437
(2021/07/16)
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- Formation of β-Ga2O3nanorings from metal-organic frameworks and their high catalytic activity for epoxidation of alkenes
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Here we report a novel synthesis of hollow high-quality β-Ga2O3 nanorings based on an interesting structural evolution from concave Ga-MOF nanodisks. The concave low-crystallinity nanodisks were constructed by non-classical crystallization with particle a
- Wang, Wei Ping,Song, Le Xin,Li, Yao,Teng, Yue,Xia, Juan,Wang, Fang,Liu, Nan Ning
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p. 349 - 357
(2021/01/14)
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- Multiscale porous single-atom Co catalysts for epoxidation with O2
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Epoxides are versatile intermediates in the production of a diverse set of chemical products. The direct epoxidation of alkenes using O2 represents an environmentally friendly and economical process to replace the use of expensive H2O2 or organic peroxides for the synthesis of epoxides. Herein, single-atom Co anchored on N-doped carbon supports with a multiscale porous structure (Co1/NC-h) has been successfully constructed by etching CoZn-ZIF metal-organic framework precursors before a carbonation process. Benefitting from the high intrinsic activity of Co-Nx active sites and the more accessibly exposed reactive sites of multiscale porous structures, the Co1/NC-h catalysts can achieve the epoxidation of cyclooctene with 95% yield of 1,2-epoxycycloheptane at 140 °C and 0.5 MPa O2. This research opens up opportunities for designing high-performance single-atom catalysts towards applications in diverse heterogeneous catalysis.
- Chen, Xiao,Gou, Wangyan,Qu, Yongquan,Zhang, Mingkai,Zhang, Sai,Zou, Yong
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p. 6016 - 6022
(2022/04/07)
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- Molybdate Stabilized Magnesium‐Iron Hydrotalcite Materials: Potential Catalysts for Isoeugenol to Vanillin and Olefin Epoxidation
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A series of molybdate-intercalated and stabilized magnesium‐iron hydrotalcite (HMFeMo) materials with different molybdate loadings were successfully prepared by an in-situ hydrothermal method. The prepared HMFeMo materials were systematically characterized using Fourier-transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), Ultraviolet-visible spectroscopy, scanning electron microscopy, thermo-gravimetric analysis, nitrogen adsorption-desorption and X-ray photoelectron spectroscopy (XPS) experiments. The XRD results demonstrated the successful intercalation of molybdate ions in the interlayer space of magnesium-iron hydrotalcite and the stabilization of the layered structure. In addition, the XPS spectra of the HMFeMo materials revealed the presence of molybdenum in a higher-valent oxidation state. The calcination of HMFeMo materials led to the formation of solid solution of mixed metal oxides. Both the as-prepared and calcined HMFeMo catalysts showed promising activity for the epoxidation of cyclooctene, as a model reaction. Furthermore, the performance of the as-prepared and calcined HMFeMo catalysts for the oxidation of a biomass model compound, namely isoeugenol to vanillin, was evaluated. The isoeugenol conversion over the as-prepared HMFeMo catalysts under solvent-free conditions and using tertiary-butyl hydroperoxide in decane as the oxidant was good. Moreover, the isoeugenol conversion and selectivity toward vanillin of HMFeMo0.1, with a molybdate loading of 0.1 mol %, were the highest (86.2% and 83.1%, respectively) of all HMFeMo catalysts in this study at 80 °C for 5 hr. HMFeMo0.1 presented the best catalytic activity for both the epoxidation of cyclooctene and oxidation of isoeugenol to vanillin, and its activity remained unchanged after several runs.
- Neethu, P. P.,Sakthivel, A.,Sreenavya, A.
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- Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
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The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
- Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
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supporting information
p. 10005 - 10013
(2021/07/19)
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- Synthesis, structure, magnetic and catalytic competency of a tetradentate (nnoo) schiff base mediated dimeric copper(ii) complex
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One dinuclear copper(II) complex {μ-[2,2 -{ethane-1,2-diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}-{μ-[2,2 -{ethane-1,2- diylbis[(azanylylidene)methanylylidene]}bis(phenolato)]}dicopper(II), [Cu2(salen)2] (1) [salen2- = [2,2 -{ethane-1,2-diylbis- [(azanylylidene)methanylylidene]}bis(phenolato)] has been isolated and characterized by X-ray diffraction analysis and spectroscopic studies. X-ray single crystal structure examination revealed that each Cu(II) center in the asymmetric unit of 1 adopts a distorted square planar geometry with a CuN2O2 chromophore, where two asymmetric units are attached through congregation of Salen involving Cu-O bond to form dinuclear molecular unit [Cu2(salen)2]. In crystalline state, these dinuclear entities in 1 are extended through C-H π interactions and π π interactions displaying a 3D network structure. The variable-temperature magnetic susceptibility measurement asserted a dominant antiferromagnetic interaction between the copper(II) centers through Cu-O-Cu linkage in 1 with J = -1.46 cm-1. The catalytic efficacy of complex 1 was studied in a series of solvents for the oxidation of styrene and cyclooctene using tert-butyl-hydroperoxide (TBHP) as an active oxidant under mild conditions. The catalytic reaction mixture has been analyzed by gas chromatography and it displayed that the yield of the epoxidation and its selectivity is optimum in acetonitrile medium.
- CHOWDHURY, HABIBAR,BERA, RAJESH,ADHIKARY, CHANDAN
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p. 1280 - 1286
(2021/06/09)
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- A stand-alone cobalt bis(dicarbollide) photoredox catalyst epoxidates alkenes in water at extremely low catalyst load
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The cobalt bis(dicarbollide) complex, Na[3,3′-Co(η5-1,2-C2B9H11) (Na[1]), is an effective photoredox catalyst for the oxidation of alkenes to epoxides in water. Advantageous features of Na[1] include its lack of photoluminescence, high solubility and surfactant behavior in aqueous media, as well as the donor ability of the carborane ligand and high oxidizing power of the Co4+/3+ couple. These features differentiate it from the well-known and widely used photosensitizer tris (2,2′-bipyridine) ruthenium(ii) ([Ru(bpy)3]2+), which also participates in electron transfer through an outer sphere mechanism. A comparison of the catalytic performance of [Ru(bpy)3]2+ with Na[1] for alkene photo-oxidation is fully in favor of Na[1], as the former shows very low or null efficiency. With a catalyst loading of 0.1 mol% conversions between 65-97% have been obtained in short reaction times, 15 minutes, with moderate selectivity for the corresponding epoxide, due to the formation of side products as diols. But when the catalyst loading is reduced to 0.01 mol%, the selectivity for the corresponding epoxide increased considerably, being the only compound formed after 15 minutes of reaction (selectivity >99%). High TON values have been obtained (TON = 8500) for the epoxidation of aromatic and aliphatic alkenes in water. We have verified that Na[3,3′-Co(η5-1,2-C2B9H11)2] acts as a photocatalyst in both the epoxidation of alkenes and in their hydroxylation in aqueous medium with a higher rate for epoxidation than for hydroxylation. Preliminary photooxidation tests using methyl oleate as the substrate led to the selective epoxidation of the double bond. These results represent a promising starting point for the development of practical methods for the processing of unsaturated fatty acids, such as the valorisation of animal fat waste using this sustainable photoredox catalyst. This journal is
- Guerrero, Isabel,Romero, Isabel,Teixidor, Francesc,Vi?as, Clara
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supporting information
p. 10123 - 10131
(2021/12/27)
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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- Investigation of physicochemical properties for novel perrhenate ionic liquid and its catalytic application towards epoxidation of olefins
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Abstract: A novel ionic liquid (IL) based on catalytic functional metal rhenium, [Smim][ReO4] (1-heptyl-3-methyl-imidazolium perrhenate) was synthesized and characterized. Density and surface tension values of the IL were determined at different temperatures, and the volume and surface properties were calculated and discussed, respectively. Furthermore, the synthesized ionic liquid [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The effect of factors of catalyst, oxidant, reaction time, and reaction temperature was discussed. The conversion of cyclohexene and cyclooctene is over 99% at optimum conditions. The IL [Smim][ReO4] as catalyst and solvent are characterized by high efficiency, long service life and recoverability, which is a better green homogeneous catalyst for epoxidation of olefins. Graphic Abstract: A novel IL based on catalytic functional metal rhenium, [Smim][ReO4] was synthesized and characterized. The volume and surface properties were calculated and discussed by the density and surface tension values at different temperatures, respectively. Furthermore, the as-synthesized [Smim][ReO4] was used as a green solvent and catalyst for homogeneous catalyzed epoxidation of olefin with urea hydrogen peroxide (UHP) oxidant. The results showed that the yield and selectivity of the reaction were up to 99%, and the catalytic efficiency of [Smim][ReO4] did not decrease significantly after five times recycling. Easy separation, recycle, nontoxicity and homogeneous catalysis are the main advantages of perrhenate ionic liquids over other heterogeneous catalysts containing organic solvents.[Figure not available: see fulltext.].
- Song, Zongren,Liu, Xueke,Zhang, Hao,Fang, Dawei,Ma, Xiaoxue
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- Organocatalytic epoxidation and allylic oxidation of alkenes by molecular oxygen
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Pyrrole-proline diketopiperazine (DKP) acts as an efficient mediator for the reduction of dioxygen by Hantzsch ester under mild conditions to allow the aerobic metal-free epoxidation of electron-rich alkenes. Mechanistic crossovers are underlined, explaining the dual role of Hantzsch ester as a reductant/promoter of the DKP catalyst and a simultaneous competitor for the epoxidation of alkenes when HFIP is used as a solvent. Expansion of this protocol to the synthesis of allylic alcohols was achieved by adding a catalytic amount of selenium dioxide as an additive, revealing a superior method to the classical application of t-BuOOH as a selenium dioxide oxidant.
- Orfanidou, Maria,Petsi, Marina,Zografos, Alexandros L.
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supporting information
p. 9172 - 9178
(2021/11/30)
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- New Cu(II), Co(II) and Ni(II) azo-Schiff base complexes: Synthesis, characterization, catalytic oxidation of alkenes and DFT study
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Three new complexes with general formula of ML (M = Cu (1), Co (2), Ni (3)) containing an azo-Schiff base ligand (H2L) derived from 2,3-butanediamine and 4-(benzeneazo) salicylaldehyde were synthesized by template method. Characterization of the ligand and complexes were accomplished with FT-IR, UV–Vis, and 1H NMR. The catalytic activity of the complexes (1–3) were tested for the oxidation of various alkenes (cyclooctene, cyclohexene, styrene, α-methyl styrene, and norbornene) applying tert-butyl hydroperoxide (TBHP) as an oxidizing agent, and it was found that they were acceptable catalysts. Under the optimized reaction conditions, CuL complex displayed 94% conversion for the oxidation of cyclooctene, and CoL and NiL complexes exhibited 90 and 85% conversions for oxidizing α-methyl styrene, respectively. Based on our density functional computations, diffuse functions are compulsory in the basis set for geometry optimization of these systems. Therefore, the most stable structures and the vibrational frequencies were calculated at the M06-2X/6–311++G(d,p) level. By establishing the correlation between observed and calculated frequencies, the assignment of the vibrational modes was performed. Based on natural charge analysis (NAO), the back electron transfer from ML to the TBHP breaks the O–O bond and facilitates the formation of tert-butoxyl radicals.
- Lashanizadegan, Maryam,Asna Ashari, Hadiseh,Sarkheil, Marzieh,Anafcheh, Maryam,Jahangiry, Samira
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- Tungsten Peroxopolyoxo Complexes as Advanced Catalysts for the Oxidation of Organic Compounds with Hydrogen Peroxide
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Selective oxidation of organic substrates by environment-friendly oxidizing agents is an important ingredient of the sustainable chemical industry. Here we report a comprehensive study in the field of metal peoroxocomplex catalysis for the selective liqui
- Baltakhinov, Vladimir P.,Berdnikova, Polina V.,Bukhtiyarov, Valerii I.,Chesalov, Yuriy A.,Khlebnikova, Tatiana B.,Kochubey, Dmitry I.,Pai, Zinaida P.,Uchenova, Yulia V.,Uslamin, Evgeny A.,Yushchenko, Dmitry Yu.
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- Fast-synthesis and catalytic property of heterogeneous Co-MOF catalysts for the epoxidation of α-pinene with air
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In the past decades, many methods have been developed for synthesizing MOFs, including solvothermal synthesis, mechanical synthesis, electrochemical synthesis, and microwave synthesis. Based on the existing research, a method is proposed for synthesizing Co-MOF by rapidly rotating hydrothermal crystallization, which largely shortens the crystallization time of Co-MOF. When the rotation speed was 150 rpm, only 2 h of crystallization time was needed to synthesize Co-MOF-150-2 with high crystallinity and stability. The optimal Co-MOF-150-2 manifested remarkable activity and selectivity for the epoxidation of α-pinene under mild conditions. The catalytic conversion of α-pinene reached the highest over the Co-MOF-150-2 catalyst, in which the conversion of α-pinene was 99.5% and the yield of 2,3-epoxypinane was 95.7%. The Co-MOF materials synthesized by the rotary method also had excellent stability and highly catalytic activity in recycling experiments. This journal is
- Zhang, Haifu,He, Jie,Lu, Xinhuan,Yang, Lu,Wang, Chenlong,Yue, Fanfan,Zhou, Dan,Xia, Qinghua
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p. 17413 - 17421
(2020/11/02)
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- Rare earth Ce- and Nd-doped spinel nickel ferrites as effective heterogeneous catalysts in the (ep)oxidation of alkenes
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Cerium (Ce)- and neodymium (Nd)-doped spinel nickel ferrites catalysts system were synthesized using a cost-effective sol–gel route. The as-prepared nickel ferrites and its doped Ce and Nd nanomaterials were characterized in terms of Fourier transform infrared spectrophotometry, X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, selected area diffraction pattern, zeta potential and magnetism techniques. Their catalytic potential was examined in the (ep)oxidation of 1,2-cyclooctene by using hydrogen peroxide (H2O2) or tert-butylhydroperoxide (t-BuOOH). Optimization of various parameters, including solvent, oxidant and catalyst type revealed that chloroform (CHCl3) or 1,2-dichloroethane as a solvent and t-BuOOH as an oxidant were found to be the best choice for this catalytic system. The catalytic efficiency was found as Nd–NiFe2O4 > Ce–NiFe2O4 > NiFe2O4. Further, the applied nanocatalysts could be easily renovated and exhibited high catalytic reactivity for 5 times of recycling experiments with long-time durability. A reasonable discussion of the mechanism reaction reinforced the action of these spinel catalysts.
- Adam, Mohamed Shaker S.,Hafez, Aly M.,Khalaf, Mai M.
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p. 3237 - 3250
(2020/07/09)
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- An oxidovanadium(IV) complex with 4,4′-di-tert-butyl-2,2′-bipyridine ligand: Synthesis, structure and catalyzed cyclooctene epoxidation
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The interaction of vanadium(III) chloride (VCl3) with 4,4′-di-tert-butyl-2,2′-bipyridine (dbbpy) in air resulted in the monomeric oxidovanadium(IV) complex [VOCl2(dbbpy)(H2O)] (1) in high yield. The complex was characterized by IR and EPR spectroscopies, by elemental analysis, and by single crystal X-ray diffraction analysis. The vanadium atom has a distorted octahedral coordination environment. The EPR spectrum of 1 in CH2Cl2 demonstrates an eight-line signal typical of vanadium(IV) with a d1 electronic configuration. Complex 1 exhibits catalytic activity in the cyclooctene oxidation with tert-butyl hydroperoxide (TBHP) in CHCl3. Detailed EPR, NMR and GC–MS studies of the reaction revealed a few mechanistic details and the nature of by-products that are generated by involvement of the chloroform solvent.
- Fomenko, Iakov S.,Vincendeau, Sandrine,Manoury, Eric,Poli, Rinaldo,Abramov, Pavel A.,Nadolinny, Vladimir A.,Sokolov, Maxim N.,Gushchin, Artem L.
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supporting information
(2019/12/28)
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- The big effect of a small change: formation of CuO nanoparticles instead of covalently bound Cu(ii) over functionalized mesoporous silica and its impact on catalytic efficiency
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Two different heterogeneous catalysts, one with Cu(ii) covalently bonded to functionalized mesoporous silica (FMS-Cu(II)) and another with CuO nanoparticles immobilized over the same silica (FMS-CuO-np), have been synthesized by a common route but with a minor alteration in the sequence of addition of reagents. It is interesting to find that by merely changing the order of the addition of reagents Cu(ii) can be incorporated into the framework in two different forms. In one case Cu(ii) binds to the N and O donor centers present in the functionalized material whereas in the other case CuO nanoparticles are generated in situ. The materials have been thoroughly characterized by powder X-ray diffraction, nitrogen adsorption/desorption, transmission electron microscopy, thermal analysis, FT-IR spectroscopy, solid state MAS-NMR spectroscopy and atomic absorption spectrophotometric studies. The synthesized products have been examined for their catalytic efficiencies in the oxidation of olefins, as a model case. Styrene, α-methyl styrene, cyclohexene, trans-stilbene and cyclooctene have been used as substrates in the presence of tert-butyl hydroperoxide as the oxidant in acetonitrile medium under mild conditions. The products of the catalytic reactions have been identified and estimated by gas chromatography and gas chromatography-mass spectrometry. The rate of conversion of the substrates for both the catalysts is high and the selectivity is also good. But from comparative studies, it is found that FMS-CuO-np which contains CuO nanoparticles shows better efficiency than FMS-Cu(II). The catalysts have been recycled for five catalytic cycles without showing much decrease in their catalytic activity. This journal is
- Das, Trisha,Nandi, Mahasweta,Singha, Debdas
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p. 10138 - 10155
(2020/08/17)
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- Double end-on azido derivative of a tridentate (NNO) Schiff base dimeric copper(II) complex: synthesis, X-ray structure, magnetic property and catalytic effectiveness
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A dimeric copper(II) complex, bis{(2-[1-(aminoethylimino)ethyl]-phenoxo}-di-μ1,1-azido-dicopper(II), [Cu2(L)2(μ2-1,1-N3)2] (1) [L = 2-[1-(aminoethylimino)ethyl]-phenoxo ion], has been isolated using a self-assembly reaction using a 1:1:1 molar ratio of Cu(NO3)2·3H2O, HL and NaN3 in methanol at room temperature and characterized through X-ray diffraction analysis and spectroscopic studies. X-ray structural analysis reveals that 1 consists of two distinct dinuclear molecular units, where each copper(II) center in the individual dinuclear unit adopts a distorted square pyramidal geometry with a CuN4O chromophore ligated through a tridentate (NNO) Schiff base and two N atoms of two different bridging azides in μ1,1-mode. Two Cu(II) centers are linked through double μ2-1,1-N3 bridges to form the dinuclear unit [Cu2(L)2(μ2-1,1-N3)2]. In the crystalline state, the dinuclear units in 1 are associated through weak intermolecular N-H?O hydrogen bonds to afford a 2-D sheet structure viewed along the crystallographic a-axis. The small magnitude of the antiferromagnetic interaction (J = –0.45 cm?1) is a result of the long Cu···Cu separation (3.205(2) ?). The catalytic efficacy of 1 was studied in a series of solvents for the epoxidation of alkenes using tert-butyl-hydroperoxide (TBHP) as an efficient oxidant under mild conditions.
- Chowdhury, Habibar,Bera, Rajesh,Rizzoli, Corrado,Adhikary, Chandan
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p. 3062 - 3078
(2020/10/29)
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- Bioinspired symmetrical and unsymmetrical diiron complexes for selective oxidation catalysis with hydrogen peroxide
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Two new symmetrical and unsymmetrical diiron(iii) complexes were synthesized and characterized by X-ray diffraction analysis, mass spectrometry, UV-visible and M?ssbauer spectroscopies. They proved to be good catalysts for alkene and alkane oxidation reactions by H2O2 in acetonitrile solution, and interesting effects of both the nature and the symmetry of the complexes were observed on catalysis in the presence of water.
- Trehoux, Alexandre,Guillot, Régis,Clemancey, Martin,Blondin, Geneviève,Latour, Jean-Marc,Mahy, Jean-Pierre,Avenier, Frédéric
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supporting information
p. 16657 - 16661
(2020/12/18)
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- Ionic liquids vs conventional solvents: A comparative study in the selective catalytic oxidations promoted by oxovanadium(IV) complexes
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Two oxovanadium(IV) complexes containing 4-acyl-5-pyrazolonate-κ2-O,O' bidentate ligands with different chain lengths in the acyl moiety, namely HQC6 (complex I) and HQC17 (complex II), have been synthetized and full characterized, to study their catalytic activity toward the mild and selective oxidation of olefins or model organosulphur substrates, promoted by H2O2 or tert-butyl hydroperoxide (TBHP). The influence due to the type of solvent, likewise ionic liquids (ILs) or conventional medium, was analysed. H2O2 has proven less efficient, in comparison to TBHP. Quantum-chemical calculations have shown that, the key catalytic species involved and, consequently, the actual mechanism might be slightly different according to the oxidant used, i.e. the peroxo VO(QMe)(O2) adduct in the case of H2O2 and the tert-butylperoxo VO(QMe)2(OOt-Bu) adduct in the case of TBHP. Preliminary calculations suggested that, in ionic liquids, the VO(QMe)2 complex might reveal relatively unstable, hence qualitatively explaining the moderate efficiency observed in these media.
- Aschi, Massimiliano,Campitelli, Patrizio,Crucianelli, Marcello,Di Nicola, Corrado,Marchetti, Fabio,Pettinari, Riccardo
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- Homogeneous catalytic oxidation of alkenes employing mononuclear vanadium complex with hydrogen peroxide
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Abstract: Homogeneous liquid-phase oxidation of alkenes (allylbenzene, cis-cyclooctene, 4-chlorostyrene, styrene, 2-norbornene, 1-methyl cyclohexene, indene, lemonine, and 1-hexene) were catalyzed by using vanadium complex [VO(hyap)(acac)2] in existence of H2O2. The complex [VO(hyap)(acac)2] was formed as a crystal by the reaction of [VO(acac)2] and 2-hydroxyacetophenone (hyap) in the presence of methanol by refluxing the reaction mixture. Various analytical and spectroscopic techniques, namely FTIR, ESI–MS, UV–Vis, single-crystal XRD, and EPR, were used to analyze and optimize the structure of the complexes. Graphic abstract: [Figure not available: see fulltext.].
- Maurya, Abhishek
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p. 3261 - 3269
(2020/07/14)
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- Method for alkene epoxidation catalyzed by ether-based rhenium ionic liquid
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The invention belongs to the technical field of ionic liquid catalysis, and specifically relates to a method for alkene epoxidation catalyzed by ether-based rhenium ionic liquid. At a certain temperature, the ether-based rhenium ionic liquid is added to a
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Paragraph 0018-0021
(2020/02/17)
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- Tuning the electronic properties of tetradentate iron-NHC complexes: Towards stable and selective epoxidation catalysts
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Two sets of bio-inspired non-heme iron complexes, each comprising of an FeII and FeIII species, bearing 16-membered macrocyclic tetradentate N-heterocyclic carbene ligands are reported. The complexes exhibit trans labile coordination sites, are characterized by means of NMR, ESI-MS, elemental analysis, SC-XRD and cyclic voltammetry and assessed as olefin epoxidation (pre-)catalysts applying H2O2 as oxidant. Sc(OTf)3 and AcOH are evaluated as Lewis and Br?nsted acidic additives, respectively, resulting in partially noticeable improvement in catalytic performance. Hereby, complex 2b shows high stability (TON = 1000 at 20 °C), high temperature tolerance and advances in the more challenging epoxidation of terminal and functionalized olefins. Furthermore, in-depth DFT calculations are conducted to put the catalysts’ structural and electronic features into relation with the catalytic results.
- B?th, Alexander D.,Bernd, Marco A.,Dyckhoff, Florian,Hofmann, Benjamin J.,Kühn, Fritz E.,Oberkofler, Jens,Reich, Robert M.,Schlagintweit, Jonas F.
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p. 548 - 561
(2020/10/21)
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- Synthesis, Crystal Structures, and Catalytic Properties of Dioxomolybdenum(VI) Complexes Derived from 4-Chloro-2-{[4-Diethylamino-2-Hydroxybenzylidene]amino}phenol
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Abstract: Two new dioxomolybdenum(VI) complexes, [MoO2L(EtOH)] (I) and [MoO2L(Sal)] (II), where L is the dianionic form of 4-chloro-2-{[4-(diethylamino)-2-hydroxybenzylidene]amino}phenol (H2L), Sal is 4-diethylaminosalicyl
- Zhu
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p. 532 - 538
(2019/07/16)
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- Highly selective and efficient olefin epoxidation with pure inorganic-ligand supported iron catalysts
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Over the past two decades, there have been major developments in the transition iron-catalyzed selective oxidation of alkenes to epoxides; a common structure found in drug, isolated natural products, and fine chemicals. Many of these approaches have enabled highly efficient and selective epoxidation of alkenes via the design of specialized ligands, which facilitates to control the activity and selectivity of the reactions catalyzed by iron atom. Herein, we report the development of the olefin epoxidation with inorganic-ligand supported iron-catalysts using 30% H2O2 as an oxidant, and the mechanism is similar to iron-porphyrin type. With the catalyst 1, (NH4)3[FeMo6O18(OH)6], various aromatic and aliphatic alkenes were successfully transformed into the corresponding epoxides with excellent yields as well as chemo- and stereo-selectivity. This catalytic system possesses the advantages of being able to avoid the use of expensive, toxic, air/moisture sensitive and commercially unavailable organic ligands. The generality of this methodology is simple to operate and exhibits high catalytic activity as well as excellent stability, which gives it the potential to be used on an industrial scale, and maybe opens a way for the catalytic oxidation reaction via inorganic-ligand coordinated iron catalysis.
- Zhou, Zhuohong,Dai, Guoyong,Ru, Shi,Yu, Han,Wei, Yongge
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supporting information
p. 14201 - 14205
(2019/10/02)
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- A hydrogen-bonded assembly of cucurbit[6]uril and [MoO2Cl2(H2O)2] with catalytic efficacy for the one-pot conversion of olefins to alkoxy products
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The reaction of the macrocyclic cavitand cucurbit[6]uril (CB[6]) and the diaqua complex [MoO2Cl2(H2O)2] in hydrochloric acid solution gave a water insoluble supramolecular compound with the general composition 2[MoO2Cl2(H2O)2]·CB[6]·xH2O·yHCl·z(CH3COCH3) (2). Single crystal X-ray diffraction (XRD) analysis revealed the presence of barrel-shape supramolecular entities, {CB[6]·10(H2O)}, aligned in layers which are shifted relative to adjacent layers to form a brick-like pattern. The CB[6]/water hydrogen-bonded entities further engage in intermolecular interactions with water, HCl and [MoO2Cl2(H2O)2] molecules to form a three-dimensional (3D) framework. Compound 2 was characterised by thermogravimetric analysis (TGA), IR and Raman vibrational spectroscopy, and 13C{1H} CP MAS NMR. The reference complex [MoO2Cl2(H2O)2]·(diglyme)2 (1) and compound 2 were studied for the oxidative catalytic conversion of olefins (cis-cyclooctene, cyclohexene and styrene) with aqueous H2O2 as oxidant. Using alcohols as solvents, 2 was employed in a one-pot two-stage strategy for converting olefins to alkoxy products, which involves oxidation (with H2O2) and acid chemistry. Mechanistic studies were carried out using different intermediates as substrates, and the type of solvent and substrate scope were investigated. The results demonstrated the ability of the CB[6]/MoVI supramolecular adduct to function as an acid-oxidation multifunctional catalyst, and its recovery and reuse via relatively simple procedures.
- Nogueira, Lucie S.,Antunes, Margarida M.,Gomes, Ana C.,Cunha-Silva, Luís,Pillinger, Martyn,Lopes, André D.,Valente, Anabela A.,Gon?alves, Isabel S.
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p. 11508 - 11519
(2019/08/07)
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- Polymer-anchored mononuclear and binuclear CuII Schiff-base complexes: Impact of heterogenization on liquid phase catalytic oxidation of a series of alkenes
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Liquid phase catalytic oxidation of a number of alkenes, for example, cyclohexene, cis-cyclooctene, styrene, 1-methyl cyclohexene and 1-hexene, was performed using polymer-anchored copper (II) complexes PS-[Cu (sal-sch)Cl] (5), PS-[Cu (sal-tch)Cl] (6), PS-[CH2{Cu (sal-sch)Cl}2] (7) and PS-[CH2{Cu (sal-tch)Cl}2] (8). Neat complexes [Cu (sal-sch)Cl] (1), [Cu (sal-tch)Cl] (2), [CH2{Cu (sal-sch)Cl}2] (3) and [CH2{Cu (sal-tch)Cl}2] (4) were isolated by reacting CuCl2·2H2O with [Hsal-sch] (I), [Hsal-tch] (II), [H2bissal-sch] (III) and [H2bissal-tch] (IV), respectively, in refluxing methanol. Complexes 1–4 have been covalently anchored in Merrifield resin through the amine nitrogen of the semicarbazide or thiosemicarbazide moiety. A number of analytical, spectroscopic and thermal techniques, such as CHNS analysis, Fourier transform-infrared, UV–Vis, PMR, 13C-NMR, electron paramagnetic resonance, scanning electron microscopy, energy-dispersive X-ray analysis, thermogravimetric analysis, atomic force microscopy, atomic absorption spectroscopy, and electrospray ionization-mass spectrometry, were used to analyze and establish the molecular structure of the ligands (I)–(IV) and complexes (1)–(8) in solid state as well as in solution state. Grafted complexes 5–8 were employed as active catalysts for the oxidation of a series of alkenes in the presence of hydrogen peroxide. Copper hydroperoxo species ([CuIII (sal-sch)-O-O-H]), which is believed to be the active intermediate, generated during the catalytic oxidation of alkenes, are identified. It was found that supported catalysts are very economical, green and efficient in contrast to their neat complexes as well as most of the recently reported heterogeneous catalysts.
- Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Mishra, Vivek Kumar,Chaudhary, Nikita,Haldar, Chanchal
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- Aerobic oxidation of the C-H bond under ambient conditions using highly dispersed Co over highly porous N-doped carbon
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Highly dispersed Co sites in highly porous N-doped carbon (Co-NC) were synthesized by high-temperature pyrolysis of Zn/Co bimetallic zeolitic imidazolate framework-8 (CoxZn100-x-ZIF). Wide characterization indicated that the pyrolysis atmosphere and temperature play crucial roles in the metal dispersion and pore structure of the resulting materials. A hydrogen treatment at elevated temperatures is found to favour the Zn volatilization and restrict the pore shrinkage of the ZIF precursor, thus yielding efficient catalysts with highly dispersed Co, a high surface area (1090 m2 g-1) and pore volume (0.89 cm3 g-1). When used as a catalyst for aerobic oxidation of ethylbenzene (EB), Co1Zn99-ZIF-800-H2 contributes to 98.9% EB conversion and 93.1% ketone selectivity under mild conditions (60 °C, 1 atm O2), which is 41.3 times more active in comparison to the ZIF-67-derived Co catalyst. Co-NC is stable and could be reused four times without obvious deactivation. This catalyst displays good chemoselectivity to the corresponding ketones when using a broad scope of hydrocarbon compounds.
- Nie, Renfeng,Chen, Jingwen,Chen, Minda,Qi, Zhiyuan,Goh, Tian-Wei,Ma, Tao,Zhou, Lin,Pei, Yuchen,Huang, Wenyu
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p. 1461 - 1466
(2019/03/26)
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- Influence of the channel size of isostructural 3d-4f MOFs on the catalytic aerobic oxidation of cycloalkenes
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The present work reports a new group of heterogeneous catalysts with a 3D structure, CuLnIDA, {[Cu3Ln2(IDA)6]·8H2O} (Ln: LaIII, GdIII or YbIII), with an organic linker (H2IDA: iminodiacetic acid). Different sets of O2 pressure and time were used in order to obtain the optimal reaction conditions at 75 °C. The reaction was found to depend on the [aldehyde]/[substrate] ratio. The best results, with a conversion of 73% for CuLaIDA as the catalyst, were obtained for the smallest ratio of 0.2. Finally, the importance of the pore size was analysed by comparing the catalytic activity of the as formed catalyst with that of the thermally activated one. The conversion increased ca. 26-35% for the different catalysts when they were previously activated. In addition, the selectivity increased towards cyclohexenone. The use of molecular oxygen as the oxidizing agent in a system where an auxiliary solvent is not used, as the cyclohexene substrate and products play the role of a solvent, permitted us to generate a more friendly environmental system for the oxidation of cycloalkenes under mild conditions.
- Cancino, Patricio,Santiba?ez, Luis,Stevens, Christian,Fuentealba, Pablo,Audebrand, Nathalie,Aravena, Daniel,Torres, Julia,Martinez, Sebastian,Kremer, Carlos,Spodine, Evgenia
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supporting information
p. 11057 - 11064
(2019/07/31)
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- New molybdenum(II) complexes with α-diimine ligands: Synthesis, structure, and catalytic activity in olefin epoxidation
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Three new complexes [Mo(η3-C3H5)Br(CO)2{iPrN=C(R)C5H4N}], where R = H (IMP = N-isopropyl 2-iminomethylpyridine), Me, and Ph, were synthesized and characterized, and were fluxional in solution. The most interesting feature was the presence, in the crystal structure of the IMP derivative, of the two main isomers (allyl and carbonyls exo), namely the equatorial isomer with the Br trans to the allyl and the equatorial with the Br trans to one carbonyl, the position trans to the allyl being occupied by the imine nitrogen atom. For the R = Me complex, the less common axial isomer was observed in the crystal. These complexes were immobilized in MCM-41 (MCM), following functionalization of the diimine ligands with Si(OEt)3, in order to study the catalytic activity in olefin epoxidation of similar complexes as homogeneous and heterogeneous catalysts. FTIR,13C- and29Si-NMR, elemental analysis, and adsorption isotherms showed that the complexes were covalently bound to the MCM walls. The epoxidation activity was very good in both catalysts for the cis-cyclooctene and cis-hex-3-en-1-ol, but modest for the other substrates tested, and no relevant differences were found between the complexes and the Mo-containing materials as catalysts.
- Vasconcellos-Dias, Maria,Marreiros, Jo?o,Sales, Rita,Félix, Vitor,Brand?o, Paula,Nunes, Carla D.,José Calhorda, Maria
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- A recyclable hybrid manganese(III) porphyrin magnetic catalyst for selective olefin epoxidation using molecular oxygen
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The synthesis and characterization of a hybrid Mn(III)-porphyrin magnetic nanocomposite is described. Moreover, a sustainable methodology for epoxidation of olefins is reported, using O2 as a green oxidant and the magnetic nanoparticle as a rec
- Dias, Lucas D.,Carrilho, Rui M.B.,Henriques, César A.,Piccirillo, Giusi,Fernandes, Auguste,Rossi, Liane M.,Filipa Ribeiro,Calvete, Mário J.F.,Pereira, Mariette M.
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p. 331 - 341
(2018/03/09)
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- Synthesis, crystal structures and catalytic property of dioxomolybdenum(VI) complexes derived from tridentate Schiff bases
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A pair of structurally similar new dioxomolybdenum(VI) complexes, [MoO2L1(EtOH)] · EtOH (1) and [MoO2L2(MeOH)] (2), where L1 and L2 are the dianionic form of 2-[(2-hydroxyphenylimino)methyl
- Zhu, Xue-Wen
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p. 939 - 945
(2019/02/15)
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- Synthesis, Crystal Structure, and Catalytic Property of a Dioxomolybdenum(VI) Complex Derived from N'-(3-Bromo-5-Chloro-2-Hydroxybenzylidene)-4-Nitrobenzohydrazide
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New dioxomolybdenum(VI) complex [MoO2(L)(CH3OH)], where L is the dianionic form of N'- (3-bromo-5-chloro-2-hydroxybenzylidene)-4-nitrobenzohydrazide (H2L), was prepared and characterized by IR and UV-Vis spectra, as well as single crystal X-ray diffraction (CIF file ССDС no. 1567063). The complex crystallizes as the monoclinic space group P21/c with unit cell dimensions a = 13.8471(10), b = 7.5618(6), c = 17.9445(12) ?, β = 90.107(2)°, V = 1878.9(2) ?3, Z = 4, R1 = 0.0821, wR2 = 0.0907, GOOF = 1.024. X-ray analysis indicates that the complex is a dioxomolybdenum(VI) species with the Mo atom in octahedral coordination. The catalytic oxidation property of the complex with tert-butylhydroperoxide in CH2Cl2 was studied.
- Zhu
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p. 421 - 424
(2018/07/06)
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- Mn(III)-Iodosylarene Porphyrins as an Active Oxidant in Oxidation Reactions: Synthesis, Characterization, and Reactivity Studies
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Mn(III)-iodosylarene porphyrin adducts, [Mn(III)(ArIO)(Porp)]+, were synthesized by reacting electron-deficient Mn(III) porphyrin complexes with iodosylarene (ArIO) at -60 °C and characterized using various spectroscopic methods. The [Mn(III)(ArIO)(Porp)]+ species were then investigated in the epoxidation of olefins under stoichiometric conditions. In the epoxidation of olefins by the Mn(III)-iodosylarene porphyrin species, epoxide was formed as the sole product with high chemoselectivities and stereoselectivities. For example, cyclohexene oxide was formed exclusively with trace amounts of allylic oxidation products; cis- and trans-stilbenes were oxidized to the corresponding cis- and trans-stilbene oxides, respectively. In the catalytic epoxidation of cyclohexene by an electron-deficient Mn(III) porphyrin complex and sPhIO at low temperature (e.g., -60 °C), the Mn(III)-iodosylarene porphyrin species was evidenced as the active oxidant that effects the olefin epoxidation to give epoxide as the product. However, at high temperature (e.g., 0 °C) or in the case of using an electron-rich manganese(III) porphyrin catalyst, allylic oxidation products, along with cyclohexene oxide, were yielded, indicating that the active oxidant(s) was not the Mn(III)-iodosylarene adduct but probably high-valent Mn-oxo species in the catalytic reactions. We also report the conversion of the Mn(III)-iodosylarene porphyrins to high-valent Mn-oxo porphyrins under various conditions, such as at high temperature, with electron-rich porphyrin ligand, and in the presence of base (OH-). The present study reports the first example of spectroscopically well-characterized Mn(III)-iodosylarene porphyrin species being an active oxidant in the stoichiometric and catalytic oxidation reactions. Other aspects, such as one oxidant versus multiple oxidants debate, also were discussed.
- Guo, Mian,Lee, Yong-Min,Seo, Mi Sook,Kwon, Yong-Ju,Li, Xiao-Xi,Ohta, Takehiro,Kim, Won-Suk,Sarangi, Ritimukta,Fukuzumi, Shunichi,Nam, Wonwoo
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supporting information
p. 10232 - 10240
(2018/08/28)
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- Ruthenium Nanoparticles Immobilized on Nano-silica Functionalized with Thiol-Based Dendrimer: A Nanocomposite Material for Oxidation of Alcohols and Epoxidation of Alkenes
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Abstract: In this work, ruthenium nanoparticles were immobilized on thiol-based dendrimer functionalized nano-silica and its catalytic activity was investigated in the oxidation reactions. To do this, silica nanoparticles were functionalized with a thiol-
- Haghshenas Kashani, Sara,Moghadam, Majid,Tangestaninejad, Shahram,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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p. 1110 - 1123
(2018/02/22)
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- Non-redox metal ions accelerated oxygen atom transfer by Mn-Me3tacn complex with H2O2 as oxygen resource
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This work demonstrates a novel strategy that the introduction of non-redox metal ions as Lewis acids to the classic dinuclear manganese complex [MnIV2(μ-O)3(Me3tacn)2](PF6)2 can greatly promote the alkene epoxidation efficiency under mild conditions with H2O2 as the solely terminal oxidant because of its economic and environmental advantages. When [MnIV2(μ-O)3(Me3tacn)2](PF6)2 was used as the catalyst in the absence of Lewis acids, only 16.4% conversion of cyclooctene with 6.2% yield of epoxide was obtained and the obvious decomposition of H2O2 was observed. However, the oxygen transfer efficiency of the catalyst was sharply improved with 100% conversion and 90.2% yield of epoxide under identical conditions when the non-redox metal ion, such as Sc3+, was introduced to the catalytic system. The novel strategy was successfully applied to the epoxidation reactions of different types of alkenes. Through UV–vis, FT-IR, EPR and CV characterizations, it was evidenced that the non-redox metal ions with high positive charge as Lewis acids could dissociate the sluggish dinuclear Mn-(μ-O)3-Mn core and the open-loop dinuclear manganese complex, HO-MnIII-(μ-O)-MnIV = O or O = MnIV-(μ-O)-MnIV = O, was proposed as the active species, which was capable of the alkene epoxidation process. This work illustrated an alternative protocol to manipulate the reactivity of those sluggish catalysts by the introduction of non-redox metal ions and provided clues to understand the role of non-redox metal ions in metalloenzymes and heterogeneous catalysts.
- Lv, Zhanao,Choe, Cholho,Wu, Yunfeng,Wang, Haibin,Chen, Zhuqi,Li, Guangxing,Yin, Guochuan
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- Six-coordinated vanadium(IV) complexes with tridentate task-specific ionic liquid Schiff base ligands: Synthesis, characterization and effect of ionic nature on catalytic activity
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By reaction of 5-(chloromethyl)salicylaldehyde with triphenylphosphine and N-methylimidazole in two separate reactions, salicylaldehydetriphenylphosphonium chloride (S2) and salicylaldehydemethylimidazolinium chloride (S3) were prepared. Reaction of 2-(aminomethyl)pyridine with these aldehydes resulted in the task-specific ionic liquid Schiff base ligands L1 and L2, respectively. Then six-coordinated vanadium(IV) Schiff base complexes of VO(acac)L1–4 were synthesized by reactions of these tridentate Schiff base ligands and VO(acac)2 in 1:1 stoichiometry. The aldehydes, ligands and VO(acac)L1–4 complexes were characterized using infrared, 1H NMR, 13C NMR, 31P NMR, UV–visible and mass spectroscopies, as well as elemental analysis. Paramagnetic property of the complexes was also studied using magnetic susceptibility measurements. The complexes were used as catalysts in epoxidation of cyclooctene and oxidation of methylphenyl sulfide and the reaction parameters were optimized. The effect of the ionic nature of the complexes was investigated in these oxidation reactions. The catalytic activity of the complexes could be varied by changing the ionic (cationic or anionic) character of VO(acac)L1–4 catalysts in which counter anion variation showed a greater effect than cationic moiety variation.
- Talouki, Somayeh Azizi,Grivani, Gholamhossein,Khalaji, Aliakbar Dehno
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- Molybdenum(II) Complexes with α-Diimines: Catalytic Activity in Organic and Ionic Liquid Solvents
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The new [MoX(η3-C3H5)(CO)2(α-diimine)] complexes with: (i) X = Br or triflate and α-diimine = 1,10-phenanthroline (phen) and dipyridophenazine (dppz); and (ii) X = Br and α-diimine = phen and dppz, with several substituents, are synthesized and characterized. The structures of [MoBr(η3-C3H5)(CO)2(Cl-phen)] and [Mo(CF3SO3)(η3-C3H5)(CO)2(dppz)] are determined by using single-crystal X-ray diffraction. These and three complexes of 2,2′-bipyridyl (bpy), and its two derivatives with Me and tBu substituents, are tested in the homogeneous catalytic epoxidation of several olefins in dichloromethane, exhibiting, in general, a good selectivity towards the respective epoxide and relatively low TOFs. For the first time, the oxidation of cis-cyclooctene with some of these catalysts is also conducted in a variety of room-temperature ionic liquids (RTILs). In the presence of [MoBr(η3-C3H5)(CO)2(phen)], the conversions, in general, increase, compared with the reactions in organic solvents. Interestingly, different chemoselectivity is found when [C6mim][Ntf2] and [C2mim][FAP] are used with diol (24–26 %). On the other hand, [MoBr(η3-C3H5)(CO)2(L)] (L = Me-phen or dppz) exhibits much lower conversions in the RTILs tested than in common organic solvents.
- Saraiva, Marta S.,Nunes, Carla D.,Félix, Vítor,Ribeiro, Ana P. C.,de Castro, Carlos Nieto,Calhorda, Maria José
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supporting information
p. 3922 - 3932
(2018/09/10)
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