- Synthesis, structure, and catalytic application of a new (3-methoxy-N-salicylidene)aniline-derived Schiff base complex of methyltrioxorhenium
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A new (3-methoxy-N-salicylidene)aniline-derived Schiff base complex of methyltrioxorhenium (C14H13NO2 ? CH 3ReO3) (I), displaying a cis-arrangement of the Schiff base ligand to the Re-bonded methyl group, has been synthesized and characterized by elemental analysis, IR, 1H NMR, and single-crystal X-ray diffraction. The X-ray diffraction analysis reveals that I crystallizes in the triclinic system, space group P, which displays a distorted trigonal-bipyramidal structure in the solid with the O- moiety binding to the Lewis acidic Re atom. The intermolecular hydrogen bands link the molecules of the complex into a two-dimensional layer structure. The presence of the π-π stacking interactions enhances the stability of the layers, which are further linked via π-π stacking interactions forming a three-dimensional supramolecular network. The unit cell parameters for I: a = 7.0032(14), b = 9.3762(19), c = 11.649(2) A, α = 84.60(3)°, β = 89.08(3)°, γ = 84.45(3)°, V = 757.9(3) A3, Z = 2, F(000) = 456, R 1 = 0.0591, ωR 2 = 0.1346. In order to study the catalytic activity of complex I, cis-cyclooctene epoxidation in dichloromethane is examined. The result shows that the electron-donating OCH3 group on the Schiff base influences the catalytic behavior significantly.
- Yue,Li,Yu,Wang,Gu,Zang
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- Molybdenum(VI) cis-dioxo complexes bearing (poly)pyrazolylmethane and -borate ligands: Syntheses, characterization and catalytic applications
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Reaction of MoO2Cl2(THF)2 with mono- (L1) and bi-dentate (L2) pyrazole type ligands leads to octahedral complexes of formula MoO2Cl2(L1)2 and MoO2Cl2(L2) (1, L1 = 3,5-Me2pz; 2, L2 = Me2C(pz)2). The structure of 2 has been determined crystallographically. Reaction of MoO2X2(THF)2 (X = (Cl or Br) with tridentate ligands (L3, e.g. tris(pyrazolyl)methane or tris(pyrazolyl)borate, leads to the replacement of both co-ordinated solvent molecules and one of the chloride ligands to give [MoO2X(L3)]X (3, X = Cl, L3 = HC(pz)3; 4, X = Br, L3 = HC(pz)3; 5, X = Cl, L3 = HC(3,5-Me2pz)3) and MoO2Cl{((pz)3BH}) 6. Depending on the donor ability and the steric bulk of the ligand, rapid rotation is observed at room temperature in some cases. At lower temperatures the structures are less fluxional. Nevertheless, bidentate and tridentate pyrazolyl ligands produce distinctly different chemical shifts in the 95Mo NMR spectra. The turnover frequencies of the described complexes in olefin epoxidation, with t-butyl hydroperoxide as oxidizing agent, are in the range of 150-460 [mol/(mol catalyst h)]. This activity is in the middle of the range observed for MoO2X2L2 complexes with N-donor ligands.
- Santos,Kuehn,Bruus-Jensen,Lucas,Romao,Herdtweck
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- Manganese(II) complexes of pyridyl-appended diazacyclo-alkanes: Effect of ligand backbone ring size on catalytic olefin oxidation
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A series of Mn(II) complexes [Mn(L)Cl2] 1-5, where L is a tetradentate 4N ligand such as N,N-bis(2-pyridylmethyl)-1,2-diaminoethane (L1A), 1,4-bis(2-pyridylmethyl)piperazine (L2), N,N-bis(2-pyridyl-methyl) hexahydropyrimidine (L3), N,N-bis(2-pyridylmethyl)-1,4-diazepane (L4) and N,N-bis(2-pyridylmethyl)-1,5-diazocane (L5), has been isolated, characterized by using electronic and ESI-MS spectral techniques and screened for catalytic olefin oxidation with a representative set of olefins. Interestingly, when the ligand N,N-bis(2-pyridylmethyl)imidazolidine (L1) is treated with MnCl 2·6H2O in methanol it undergoes imidazolidine ring hydrolysis to form the complex [Mn(L1A)Cl2] possessing a distorted octahedral coordination geometry around Mn(II). The complex [Mn(L3)(OTf) 2(H2O)] contains Mn(II) with a distorted pentagonal bipyramidal coordination geometry while [Mn(L4)Cl2] contains Mn(II) with an octahedral coordination geometry. The complex [Mn(L5)Cl2] adopts a rare trigonal prismatic coordination geometry, presumably because of steric interactions imposed by the ligand backbone. The catalytic ability of the solvent coordinated complex species [Mn(L)(ACN)2]2+ show significant activity towards olefin epoxidation using iodosylbenzene (PhIO) as oxygen source and addition of N-methylimidazole to the reaction mixture increases the epoxide yield. The epoxidation of cis-cyclooctene catalyzed by the complexes proceeds with high conversion (22-65%) and selectivity (100%). The epoxide yield and product selectivity increase upon increasing the Lewis acidity of the Mn(II) center, as modified by the variation in the diazacycloalkane ligand backbone.
- Saravanan, Natarajan,Palaniandavar, Mallayan
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- Rearrangement of the trans-tricyclo[4.2.0.01,3]oct-4-enyl skeleton
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The acetolysis of a tosylate with a novel tricyclic skeleton was examined. Two major products (a tosylate and an acetate) are formed and both are the result of a skeletal rearrangement. A mechanism to account for the observed products is proposed and preliminary kinetic data are reported. (C) 2000 Elsevier Science Ltd.
- Koltun, Elena S.,Kass, Steven R.
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- Epoxidation of olefins with hydrogen peroxide catalyzed by a reusable lacunary-type phosphotungstate catalyst
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Olefins and allylic alcohols have been epoxidized with commercially available hydrogen peroxide (30% H2O2) using a phase transfer catalyst, composed of cetyltrimethylammonium cations and a lacunary-type phosphotungstate anion [PW11O39] 7- or the complete Keggin-type heteropolyanion [PW12O 40]3-, under two-phase conditions using ethyl acetate as the solvent. It was found that the lacunary-type catalyst showed higher activity and better recyclability than the complete Keggin-type catalyst under the same reaction conditions. 31P NMR spectroscopy and solubility measurements for the two catalysts revealed that the [PW11O39] 7- anion had a much faster degradation rate than the [PW 12O40]3- anion in an excess of H 2O2, which resulted in the formation of more catalytically active species. As a result, the lacunary-type phosphotungstate anion-based catalyst gave a better catalytic performance than the complete Keggin-type anion in ethyl acetate. Science China Press and Springer-Verlag Berlin Heidelberg 2011.
- Hua, Li,Qiao, Yunxiang,Li, Huan,Feng, Bo,Pan, Zhenyan,Yu, Yinyin,Zhu, Wenwen,Hou, Zhenshan
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- Catalytic aerobic oxidation of cycloalkanes with nanostructured amorphous metals and alloys
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Under mild conditions (40 atm O2, 28?°C, 10-15 h), an efficient aerobic oxidation of cycloalkanes to cycloalkanols can be achieved using nanostructured amorphous metals such as Fe and Co and an amorphous alloy like Fe20Ni80 as catalysts. For example, cyclohexane is oxidized to cyclohexanol with 32-41% conversion, while 1-adamantanol is formed from adamantane with 52-57% conversion.
- Kesavan, Venkitasamy,Sivanand, Pennadam S.,Chandrasekaran, Srinivasan,Koltypin, Yuri,Gedanken, Aharon
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- Single crystal EPR spectroscopy, magnetic studies and catalytic activity of a self-assembled [2 × 2] CuII4 cluster obtained from a carbohydrazone based ligand
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A new tetranuclear [2 × 2] cluster of Cu(II) with a symmetric carbohydrazone based ligand, [Cu4L4](NO3)4·1.6(H2O) (1), {where HL donates bis-[(E)-N'-(1-(pyridin-2-yl)ethylidene)]carbohydrazide} was synthesized and characterized by spectroscopic methods and X-ray analysis. The EPR spectra were performed on single crystals of complex 1 at various temperatures and allowed the identification and separation of two types of magnetic objects contributing to magnetism: single atoms of Cu(II) and a tetranuclear Cu4 cluster. The main values of the g-factor and hyperfine structure were determined for single ions of Cu(II). The copper atoms in the tetramer are coupled antiferromagnetically with an isotropic antiferromagnetic exchange J = 215 K (149.4 cm-1). A small anisotropic exchange of the order of 0.06 K (0.04 cm-1) is responsible for the initial zero-field splitting of the energy levels in the tetramer spectrum. Magnetic measurements of complex 1 confirmed the existence of a strong antiferromagnetic exchange coupling between four Cu(II) ions. Complex 1 showed high potential for the catalytic and selective oxidation of cis-cyclooctene with aqueous H2O2.
- Bikas, Rahman,Hosseini-Monfared, Hassan,Aleshkevych, Pavlo,Szymczak, Ritta,Siczek, Milosz,Lis, Tadeusz
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- Synthesis of a light-harvesting ruthenium porphyrin complex substituted with BODIPY units. Implications for visible light-promoted catalytic oxidations
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A light-harvesting ruthenium porphyrin substituted covalently with four boron-dipyrrin (BODIPY) moieties has been synthesized and studied. The resulting complex showed an efficient decarbonylation reaction predominantly due to a photo-induced energy transfer process. Chemical oxidation of the ruthenium(ii) BODIPY-porphyrin afforded a high-energytrans-dioxoruthenium(vi) species that is one order of magnitude more reactive towards alkene oxidation than those analogues supported by conventional porphyrins. In the presence of visible light, the ruthenium(ii) BODIPY-porphyrin displayed remarkable catalytic activity toward sulfide oxidation and alkene epoxidation using iodobenzene diacetate [PhI(OAc)2] and 2,6-dichloropyridineN-oxide (Cl2pyNO) as terminal oxidants, respectively. The findings in this work highlight that porphyrin-BODIPY conjugated metal complexes are potentially useful for visible light-promoted catalytic oxidations.
- Malone, Jonathan,Klaine, Seth,Alcantar, Christian,Bratcher, Fox,Zhang, Rui
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p. 4977 - 4985
(2021/03/26)
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- Activation of hydrogen peroxide by the nitrate anion in micellar media
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We present the activation of hydrogen peroxide by micellar imidazolium nitratesviaH-bond formation in water, as shown by vibrational spectroscopy and supported by DFT calculations. Mechanistic insight into the interactions of the surfactant cation, the nitrate anion and H2O2is given. The micelles solubilise and epoxidise cyclooctene in the aqueous phase.
- Schmidt, Fabian,Zehner, Bastian,Kaposi, Marlene,Drees, Markus,Mink, János,Korth, Wolfgang,Jess, Andreas,Cokoja, Mirza
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supporting information
p. 1965 - 1971
(2021/03/26)
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- Ruthenium-Catalyzed Dehydrogenation Through an Intermolecular Hydrogen Atom Transfer Mechanism
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The direct dehydrogenation of alkanes is among the most efficient ways to access valuable alkene products. Although several catalysts have been designed to promote this transformation, they have unfortunately found limited applications in fine chemical synthesis. Here, we report a conceptually novel strategy for the catalytic, intermolecular dehydrogenation of alkanes using a ruthenium catalyst. The combination of a redox-active ligand and a sterically hindered aryl radical intermediate has unleashed this novel strategy. Importantly, mechanistic investigations have been performed to provide a conceptual framework for the further development of this new catalytic dehydrogenation system.
- Huang, Lin,Bismuto, Alessandro,Rath, Simon A.,Trapp, Nils,Morandi, Bill
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supporting information
p. 7290 - 7296
(2021/03/01)
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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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- Oxoiron(v) mediated selective electrochemical oxygenation of unactivated C-H and CC bonds using water as the oxygen source
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An efficient electrochemical method for the selective oxidation of C-H bonds of unactivated alkanes (BDE ≤97 kcal mol-1) and CC bonds of alkenes using a biomimetic iron complex, [(bTAML)FeIII-OH2]-, as the redox mediator in an undivided electrochemical cell with inexpensive carbon and nickel electrodes is reported. The O-atom of water remains the source of O-incorporation in the product formed after oxidation. The products formed upon oxidation of C-H bonds display very high regioselectivity (75:1, 3°:2° for adamantane) and stereo-retention (RC ~99% for cyclohexane derivatives). The substrate scope includes natural products such as cedryl acetate and ambroxide. For alkenes, epoxides were obtained as the sole product. Mechanistic studies show the involvement of a high-valent oxoiron(v) species, [(bTAML)FeV(O)]- formed via PCET (overall 2H+/2e-) from [(bTAML)FeIII-OH2]- in CPE at 0.80 V (vs. Ag/AgNO3). Moreover, electrokinetic studies for the oxidation of C-H bonds indicate a second-order reaction with the C-H abstraction by oxoiron(v) being the rate-determining step.
- Chandra, Bittu,Gupta, Sayam Sen,Hellan, K. M.,Pattanayak, Santanu
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p. 11877 - 11885
(2020/11/18)
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- Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2
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A novel type of hybrid catalytic materials [MnII-L?BC] has been developed using biochar (BC) as support material for covalent grafting of a MnII Schiff-base catalyst (MnII-L). The hybrid [MnII-L?BC] materials have been evaluated for an important catalytic process, epoxidation of olefins using H2O2 as oxidant. A number of different substrates were used, with cyclohexene achieving the highest yields. When compared to the non-grafted, homogeneous MnII-L, the hybrid catalysts [MnII-L?BC] show a significant enhancement of the catalytic efficiency i.e. as documented by the increase of Turnover Numbers (TONs) (826 for [MnII-L-SS550ox] and 822 for [MnII-L-SW550ox]) and Turnover Frequencies (TOFs) (551 h?1 for [MnII-L-SS550ox] and 411 h?1 for [MnII-L-SW550ox]). The interfacial catalytic mechanism and the role of the BC support have been analyzed by Raman and Electron Paramagnetic Resonance spectroscopies. Based on these data we discuss a mechanism where the high efficiency of the hybrid materials involves the biochar carbon layers acting as promoters of the substrate and products kinetics. To a broader context, this work exemplifies that biochar-based hybrid materials are potent for oxidative catalysis technologies.
- Borges Regitano, Jussara,Deligiannakis, Yiannis,Gemenetzi, Aikaterini,Louloudi, Maria,Mavrogiorgou, Alexandra,Pierri, Leticia
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- Catalytic performance of bulk and colloidal Co/Al layered double hydroxide with Au nanoparticles in aerobic olefin oxidation
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A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.
- Leandro, Sónia R.,Fernandes, Cristina I.,Viana,Mourato,Vaz, Pedro D.,Nunes, Carla D.
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- Design of peptide-containing: N 5-unmodified neutral flavins that catalyze aerobic oxygenations
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Simulation of the monooxygenation function of flavoenzyme (Fl-Enz) has been long-studied with N5-modified cationic flavins (FlEt+), but never with N5-unmodified neutral flavins (Fl) despite the fact that Fl is genuinely equal to the active center of Fl-Enz. This is because of the greater lability of 4a-hydroperoxy adduct of Fl, FlOOH, compared to those of FlEt+, FlEtOOH, and Fl-Enz, FlOOH-Enz. In this study, Fl incorporated into a short peptide, flavopeptide (Fl-Pep), was designed by a rational top-down approach using a computational method, which could stabilize the corresponding 4a-hydroperoxy adduct (FlOOH-Pep) through intramolecular hydrogen bonds. We report catalytic chemoselective sulfoxidation as well as Baeyer-Villiger oxidation by means of Fl-Pep under light-shielding and aerobic conditions, which are the first Fl-Enz-mimetic aerobic oxygenation reactions catalyzed by Fl under non-enzymatic conditions.
- Arakawa, Yukihiro,Yamanomoto, Ken,Kita, Hazuki,Minagawa, Keiji,Tanaka, Masami,Haraguchi, Naoki,Itsuno, Shinichi,Imada, Yasushi
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p. 5468 - 5475
(2017/08/01)
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- Activated vs. pyrolytic carbon as support matrix for chemical functionalization: Efficient heterogeneous non-heme Mn(II) catalysts for alkene oxidation with H2O2
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Two types of heterogeneous catalytic materials, MnII-L3imid@Cox and MnII-L3imid@PCox, have been synthesized and compared by covalent grafting of a catalytically active [MnII-L3imid] complex on the surface of an oxidized activated carbon (Cox) and an oxidized pyrolytic carbon from recycled-tire char (PCox). Both hybrids are non-porous bearing graphitic layers intermixed with disordered sp2/sp3 carbon units. Raman spectra show that (ID/IG)activatedcarbon > (ID/IG)pyrolyticcarbon revealing that oxidized activated carbon(Cox) is less graphitized than oxidized pyrolytic carbon (PCox). The MnII-L3imid@Cox and MnII-L3imid@PCox catalysts were evaluated for alkene oxidation with H2O2 in the presence of CH3COONH4. Both showed high selectivity towards epoxides and comparing the achieved yields and TONs, they appear equivalent. However, MnII-L3imid@PCox catalyst is kinetically faster than the MnII-L3imid@Cox (accomplishing the catalytic runs in 1.5 h vs. 5 h). Thus, despite the similarity in TONs MnII-L3imid@PCox achieved extremely higher TOFs vs. MnII-L3imid@Cox. Intriguingly, in terms of recyclability, MnII-L3imid@Cox could be reused for a 2th run showing a ~20% loss of its catalytic activity, while MnII-L3imid@PCox practically no recyclable. This phenomenon is discussed in a mechanistic context; interlinking oxidative destruction of the Mn-complex with high TOFs for MnII-L3imid@PCox, while the low-TOFs of MnII-L3imid@Cox are preventive for the oxidative destruction of the Mn-complex.
- Simaioforidou,Papastergiou,Margellou,Petrakis,Louloudi
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p. 516 - 525
(2016/12/16)
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- Molecular heterogeneous catalysts derived from bipyridine-based organosilica nanotubes for C-H bond activation
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Heterogeneous metal complex catalysts for direct C-H activation with high activity and durability have always been desired for transforming raw materials into feedstock chemicals. This study described the design and synthesis of one-dimensional organosilica nanotubes containing 2,2′-bipyridine (bpy) ligands in the framework (BPy-NT) and their post-synthetic metalation to provide highly active and robust molecular heterogeneous catalysts. By adjusting the ratios of organosilane precursors, very short BPy-NT with ~50 nm length could be controllably obtained. The post-synthetic metalation of bipyridine-functionalized nanotubes with [IrCp?Cl(μ-Cl)]2 (Cp? = η5-pentamethylcyclopentadienyl) and [Ir(cod)(OMe)]2 (cod = 1,5-cyclooctadiene) afforded solid catalysts, IrCp?-BPy-NT and Ir(cod)-BPy-NT, which were utilized for C-H oxidation of heterocycles and cycloalkanes as well as C-H borylation of arenes. The cut-short nanotube catalysts displayed enhanced activities and durability as compared to the analogous homogeneous catalysts and other conventional heterogeneous catalysts, benefiting from the isolated active sites as well as the fast transport of substrates and products. After the reactions, a detailed characterization of Ir-immobilized BPy-NT via TEM, SEM, nitrogen adsorption, UV/vis, XPS, and 13C CP MAS NMR indicated the molecular nature of the active species as well as stable structures of nanotube scaffolds. This study demonstrates the potential of BPy-NT with a short length as an integration platform for the construction of efficient heterogeneous catalytic systems for organic transformations.
- Zhang, Shengbo,Wang, Hua,Li, Mei,Han, Jinyu,Liu, Xiao,Gong, Jinlong
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p. 4489 - 4496
(2017/07/11)
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- Mn-Schiff base modified MCM-41, SBA-15 and CMK-3 NMs as single-site heterogeneous catalysts: Alkene epoxidation with H2O2 incorporation
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The development of new functional catalytic materials prepared via appropriate chemical modification of mesoporous silica SBA-15, MCM-41 or carbon nanomaterials CMK-3, are presented. Their synthesis has been carried out via two synthetic approaches: (a) a two steps procedure which includes grafting of the Schiff base ligand 1,3-bis[3-aza-3-(1-methyl-3-oxobut-1-enyl)-prop-3-en-1-yl]-2-(4-hydroxy-phenyl)-1,3-imidazolidine (L) onto the suppors and subsequent metalation of the so-formed hybrid material, and (b) an one step procedure which allows covalent grafting of the entire [MnII-Schiff base] catalyst onto the carbonaceous support. The resulting single-site heterogeneous catalysts were characterized and evaluated for alkene epoxidation with H2O2 in the presence of CH3COONH4 as additive. They are efficient and selective towards formation of epoxides. The highest TONs have been achieved by L@MCM-41-MnII and MnII-L@CMK-3. Moreover, MnII-L@CMK-3 is operative for a second use and kinetically very fast, demonstrating remarkably high TOFs 65-634 h-1 that is correlated to its practically zero porosity. Based on the present data, the textural features of the obtained catalysts are discussed in correlation with their catalytic performance.
- Mavrogiorgou,Baikousi,Costas,Mouzourakis,Deligiannakis,Karakassides,Louloudi
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- Recyclable, green and efficient epoxidation of olefins in water with hydrogen peroxide catalyzed by polyoxometalate nanocapsule
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A practical method for the selective epoxidation of alkenes was discovered using HxPMo12O40 H4Mo72Fe30(CH3COO)15O254 as a catalyst in the presence of H2O2 as a green oxidant. However, the simple catalyst system involving polyoxometalates and H2O2 exercised the most successful system in obtaining high to excellent yields of epoxide products for different alkenes, including aromatic and aliphatic alkenes at room temperature in water. The effectiveness of this catalyst is evidenced by 99% selectivity to epoxide and 97-99% efficiency of H2O2 utilization. The stability of PMo > Mo72Fe30 under a catalytic reaction has been confirmed by XRD, FT-IR and Raman spectroscopies.
- Fareghi-Alamdari, Reza,Hafshejani, Shahrbanou Moradpour,Taghiyar, Hamid,Yadollahi, Bahram,Farsani, Mostafa Riahi
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- Comparative study of the catalytic thermodynamic barriers for two homologous Mn- and Fe-non-heme oxidation catalysts
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Two sets of homologous Mn- and Fe-catalysts, [MnIILCl2], [FeIILCl2] and [MnIIL(OAc)2], [FeIIL(OAc)2] have been synthesized. A detailed comparative study of their catalytic oxidative performance with H2O2, in tandem with EPR and Low-Temperature UV–vis spectroscopies has been carried out. The [Metal-L(OAc)2] and [Metal-LCl2] catalysts did not show any difference in their catalytic behavior i.e. there is no effect of the labile ligands on the studied catalysis. It is found that the Mn-catalysts consistently outcompeted the homologous Fe-catalysts i.e. TOFs (Mn) = 162 vs. TOFs (Fe) = 16. We found that the Fe-catalyst faces a significantly higher activation barrier than the Mn-catalyst i.e. Ea(FeIIL(OAC)2) = 91KJ/mol ? Ea(MnIIL(OAC)2) = 55 kJ/mole, while the free-energy difference, ΔG(FeIIL(OAC)2) ~ ΔG(MnIIL(OAC)2) ~ ?145 kJ/mole, did not make difference. Taken altogether the present data clarify that the main thermodynamic barrier, ultimately determining the overall catalytic performance, of these homologous Mn- and Fe-catalysts is the activation energy for the transient intermediates i.e. MnII to MnIV[Formula presented] for the Mn-catalysts and FeII to FeIII[Formula presented] for the Fe-catalysts. A unified/consistent catalytic thermodymanic concept is discussed, that bears relevance to the catalytic behavior of many non-heme Mn- vs. Fe-oxidation catalysts.
- Papastergiou,Stathi,Milaeva,Deligiannakis,Louloudi
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p. 104 - 115
(2016/07/21)
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- Oxidation of olefins using atmospheric oxygen atoms initiated by tert -butylhydroperoxide or hydrogen peroxide with silver nanoparticles deposited on MCM-41 as catalysts
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Silver nanosized particles were grown on the surface and in the channels of mesoporous silica (MCM-41) by stirring a mixture of AgNO3 and polyvinylpyrrolidone (PVP) in ethylene glycol in a 1:20 weight ratio with MCM-41 for 1 h. The heterogeneous product was analysed by BET surface area and X-ray powder diffraction measurements, as well as TEM images which indicated that 5 to 20 nm sized Ag particles were on the surface of MCM-41. The dried material, suspended in a mixture of 1,2-dichloroethane and acetonitrile and in the presence of tBuOOH held at 80 °C for 24 h, was capable of the oxidation of the olefins (Z)-cyclooctene, cyclohexene, styrene and indene resulting in a variety of oxidized products. Comparable oxidation was also accomplished in a green solvent mixture consisting of 3% NaCl dissolved in H2O and tBuOH (1:1 by volume). The catalyst was active for five sequential cycles. After the first cycle, H2O2 instead of tBuOOH could be used as the radical initiator as the Ag nanoparticles were passivated by the formation of AgCl on the surface. This research illustrates a method of oxygen activation allowing for the transfer of an oxygen atom from the atmosphere onto an olefin, presumably via the formation of a peroxide radical.
- Chen, Zhichao,Luck, Rudy L.
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p. 3354 - 3359
(2016/06/13)
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- A biomimetic oxidation catalyzed by manganese(III) porphyrins and iodobenzene diacetate: Synthetic and mechanistic investigations
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Abstract With iodobenzene diacetate [PhI(OAc)2] as the oxygen source, manganese(III) porphyrin complexes exhibit remarkable catalytic activity toward the selective oxidation of alkenes and activated hydrocarbons. Conspicuous is the fact that the readily soluble PhI(OAc)2 in the presence of a small amount of water is more efficient than the commonly used PhIO and other oxygen sources under same catalytic conditions. High selectivity for epoxides and excellent catalytic efficiency with up to 10,000 TON have been achieved in alkene epoxidations. It was found that the reactivity of manganese(III) porphyrin catalysts was greatly affected by axial ligand and the weakly binding perchlorate gave the highest catalytic activity in the epoxidation of alkenes. A manganese(IV)-oxo porphyrin was detected in the reaction of the manganese(III) porphyrin and PhI(OAc)2. However, our catalytic competition and Hammett studies have suggested that the more reactive manganese(V)-oxo intermediate was favored as the premier active oxidant, even it is too short-lived to be produced in detectable concentrations.
- Kwong, Ka Wai,Chen, Tse-Hong,Luo, Weilong,Jeddi, Haleh,Zhang, Rui
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p. 176 - 183
(2015/04/14)
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- Olefin epoxidation with hydrogen peroxide using octamolybdate-based self-separating catalysts
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Mo8O264- based organic polyoxomolybdate salts of general formula [Hmim]4Mo8O26 (Hmim = 1-hexyl-3-methylimidazolium), [Dhmim]4Mo8O26 (Dhmim = 1,2-dimethyl-3-hexylimidazolium) and [Hpy]4Mo8O26·H2O (Hpy = 1-hexylpyridinium) have been prepared and characterized. These compounds were applied as catalysts for olefin epoxidation using hydrogen peroxide (H2O2) as oxidant in CH3CN. The polyoxomolybdate salts exhibit excellent catalytic performance and are also self-separating, a great advantage for catalyst recycling. The catalysts can be reused for at least 10 runs without significant loss of activity. This journal is
- Zhou, Ming-Dong,Liu, Mei-Ju,Huang, Liang-Liang,Zhang, Jian,Wang, Jing-Yun,Li, Xue-Bing,Kühn, Fritz E.,Zang, Shu-Liang
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p. 1186 - 1193
(2015/03/04)
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- Immobilisation of a molecular epoxidation catalyst on UiO-66 and -67: the effect of pore size on catalyst activity and recycling
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Amino-functionalised metal-organic frameworks UiO-66 and -67 were post-synthetically modified with salicylaldehyde. A molybdenum complex was immobilised on the resulting materials. They were characterised by 13C-MAS-NMR, XPS and PXRD to confirm immobilisation and stability. The immobilised complex is an active and reusable catalyst for olefin epoxidation with tert-butyl hydroperoxide (TBHP) as an oxidant. It is shown that the effective pore size, probed with Brunauer-Emmett-Teller (BET) surface area analysis and the number of amino groups affect the diffusion of reactants and products, as well as catalyst recycling.
- Kaposi, Marlene,Cokoja, Mirza,Hutterer, Christine H.,Hauser, Simone A.,Kaposi, Tobias,Klappenberger, Florian,P?thig, Alexander,Barth, Johannes V.,Herrmann, Wolfgang A.,Kühn, Fritz E.
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p. 15976 - 15983
(2015/09/15)
-
- Synthesis, characterization, magnetic and catalytic properties of a ladder-shaped MnII coordination polymer
-
[Mn(LH)(H2O)]n {1, where LH2- is the dianion of N-(4-carboxybenzyl)iminodiacetic acid} has been synthesized and its crystal structure has been determined. The crystal of 1 is built from 1D polymeric ladder-shaped chains that extend to a 3D supramolecular architecture through H-bonds. The compound was characterized with spectroscopic and physicochemical techniques. Variable-temperature magnetic data suggest that there are weak antiferromagnetic interactions. Compound 1 has been evaluated as a heterogeneous oxidation catalyst. It catalyzes alkene epoxidation selectively in relatively high yields.
- Lymperopoulou, Smaragda,Papastergiou, Maria,Louloudi, Maria,Raptopoulou, Catherine P.,Psycharis, Vassilis,Milios, Constantinos J.,Plakatouras, John C.
-
p. 3638 - 3644
(2015/05/05)
-
- Making Fe(BPBP)-catalyzed C-H and CC oxidations more affordable
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The limited availability of catalytic reaction components may represent a major hurdle for the practical application of many catalytic procedures in organic synthesis. In this work, we demonstrate that the mixture of isomeric iron complexes [Fe(OTf)2(mix-BPBP)] (mix-1), composed of Λ-α-[Fe(OTf)2(S,S-BPBP)] (S,S-1), Δ-α- [Fe(OTf)2(R,R-BPBP)] (R,R-1) and Δ/Λ-β-[Fe(OTf) 2(R,S-BPBP)] (R,S-1), is a practical catalyst for the preparative oxidation of various aliphatic compounds including model hydrocarbons and optically pure natural products using hydrogen peroxide as an oxidant. Among the species present in mix-1, S,S-1 and R,R-1 are catalytically active, act independently and represent ca. 75% of mix-1. The remaining 25% of mix-1 is represented by mesomeric R,S-1 which nominally plays a spectator role in both C-H and C=C bond oxidation reactions. Overall, this mixture of iron complexes displays the same catalytic profile as its enantiopure components that have been previously used separately in sp3 C-H oxidations. In contrast to them, mix-1 is readily available on a multi-gram scale via two high yielding steps from crude dl/meso-2,2′-bipyrrolidine. Next to its use in C-H oxidation, mix-1 is active in chemospecific epoxidation reactions, which has allowed us to develop a practical catalytic protocol for the synthesis of epoxides.
- Yazerski, Vital A.,Spannring, Peter,Gatineau, David,Woerde, Charlotte H.M.,Wieclawska, Sara M.,Lutz, Martin,Kleijn, Henk,Klein Gebbink, Robertus J.M.
-
supporting information
p. 2062 - 2070
(2014/03/21)
-
- Tuning the olefin epoxidation by manganese(iii) complexes of bisphenolate ligands: Effect of Lewis basicity of ligands on reactivity
-
A new family of manganese(iii) complexes of the type [Mn(L)Cl], where H2L is 1,4-bis(2-hydroxy-benzyl)-1,4-diazepane (H2(L1)), 1,4-bis(2-hydroxy-4-methylbenzyl)-1,4-diazepane (H2(L2)), 1,4-bis(2-hydroxy-3,5-dimethylbenzyl)-1,4-diazepane (H2(L3)) and 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-1,4-diazepane (H2(L4)), has been isolated and studied as a catalyst for epoxidation reaction. Complexes 1-4 have been characterized using elemental analysis, electronic spectral and electrochemical methods and ESI-MS. The single crystal X-ray structures of 1 and 3 contain the MnN2O2Cl chromophore with a novel square pyramidal coordination geometry (τ: 1, 0.11; 3, 0.00). All the complexes possess a distorted square pyramidal coordination geometry in solution, as revealed by the characteristic bands observed in the electronic spectra. A time dependent density functional theory (TD-DFT) calculation has been performed to assist in the assignment of the electronic absorption spectral bands of the complexes. The Mn(iii)/Mn(ii) redox potentials (E1/2) of 1-4 fall within the narrow range of 0.279-0.320 V. The catalytic ability of the complexes towards olefin epoxidation has been investigated using PhIO as the oxygen source at room temperature under an N2 atmosphere. Addition of N-methylimidazole to the reaction mixture leads to an increase in the epoxide yield. A correlation between the Lewis acidity of the Mn(iii) center as tuned by the substituents on the phenolate ligand, and the epoxide yield and product selectivity has been observed. The present complexes act as better chemoselective catalysts for epoxidation of cyclohexene and styrene rather than cyclooctene.
- Sankaralingam, Muniyandi,Palaniandavar, Mallayan
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p. 538 - 550
(2014/01/06)
-
- Cyclopentadienyl molybdenum alkyl ester complexes as catalyst precursors for olefin epoxidation
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New molybdenum complexes of the type [CpMo(CO)3X] containing ligands of the formula X = CHR2CO(OR1) where R1 = ethyl (1), menthyl (4), and bornyl (5) and R2 = H; R1 = ethyl and R2 = methyl (2) and phenyl (3) have been synthesized and characterized by NMR and IR spectroscopy and X-ray crystallography. These compounds have been applied as catalyst precursors for achiral and chiral epoxidation of unfunctionalized olefins with tert-butyl hydroperoxide (TBHP) as the oxidant at 22 °C (in CH2Cl2) and 55°C (in CHCl3). The substrates cis-cyclooctene, 1-octene, cis- and trans-stilbene, and trans-β-methylstyrene were selectively and quantitatively converted into their epoxides using a catalyst:substrate:oxidant ratio of 1:100:200 within 4 h at room temperature in CH2Cl2 and within 15 min at 55°C in CHCl3. Complexes 1-5 are precursors of active epoxidation catalysts and turnover frequencies (TOFs) of ca. 1200 h-1 are obtained with cis-cyclooctene as the substrate. No enantioselectivity is observed with trans-β-methylstyrene as the substrate despite the application of enantiomerically pure precatalysts. In situ monitoring of catalytic epoxidation of cis-cyclooctene with complex 5 by 1H and 13C NMR spectroscopy suggests that the chiral alkyl ester side chain is retained during oxidation with TBHP. During epoxidation, the primary catalytic species is the dioxo complex [CpMoO2X]. After near complete conversion of cis-cyclooctene to its epoxide, further oxidation of the dioxo complex to oxo-peroxo complex [CpMo(η2-O2)(O)X] takes place. The oxo-peroxo complex is also an active epoxidation catalyst.
- Grover, Nidhi,P?thig, Alexander,Kühn, Fritz E.
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p. 4219 - 4231
(2015/01/09)
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- Activated carbon functionalized with Mn(II) Schiff base complexes as efficient alkene oxidation catalysts: Solid support matters
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A new synthetic methodology to covalently anchor MnII-Schiff- base catalysts onto activated carbon (ACox) has been applied resulting in heterogeneous MnII-L@ACox materials. These catalysts are effective and selective towards epoxides with H2O2, in the presence of CH3COONH4, as co-catalyst, providing TONs equivalent-to/or higher than the homologous MnII-L@SiO2 catalysts for certain substrates. Moreover MnII-L@ACox catalysts are re-usable and kinetically faster than the corresponding MnII- L@SiO2 catalysts resulting in considerably higher TOFs. Combining catalytic and EPR spectroscopic data we propose a catalytic reaction mechanism which elucidates the co-catalytic function of CH3COONH4 which is of key importance for the successful performance of the studied Mn II-catalysts.
- Mavrogiorgou,Papastergiou,Deligiannakis,Louloudi
-
-
- Synthesis, characterization, magnetic and catalytic properties of a ladder-shaped MnII coordination polymer
-
[Mn(LH)(H2O)]n {1, where LH2- is the dianion of N-(4-carboxybenzyl)iminodiacetic acid} has been synthesized and its crystal structure has been determined. The crystal of 1 is built from 1D polymeric ladder-shaped chains that extend to a 3D supramolecular architecture through H-bonds. The compound was characterized with spectroscopic and physicochemical techniques. Variable-temperature magnetic data suggest that there are weak antiferromagnetic interactions. Compound 1 has been evaluated as a heterogeneous oxidation catalyst. It catalyzes alkene epoxidation selectively in relatively high yields. Copyright
- Lymperopoulou, Smaragda,Papastergiou, Maria,Louloudi, Maria,Raptopoulou, Catherine P.,Psycharis, Vassilis,Milios, Constantinos J.,Plakatouras, John C.
-
p. 3638 - 3644
(2014/08/18)
-
- Synthesis, Characterization, Magnetic and Catalytic Properties of a Ladder-Shaped MnII Coordination Polymer
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[Mn(LH)(H2O)]n {1, where LH2- is the dianion of N-(4-carboxybenzyl)iminodiacetic acid} has been synthesized and its crystal structure has been determined. The crystal of 1 is built from 1D polymeric ladder-shaped chains that extend to a 3D supramolecular architecture through H-bonds. The compound was characterized with spectroscopic and physicochemical techniques. Variable-temperature magnetic data suggest that there are weak antiferromagnetic interactions. Compound 1 has been evaluated as a heterogeneous oxidation catalyst. It catalyzes alkene epoxidation selectively in relatively high yields.
- Lymperopoulou, Smaragda,Papastergiou, Maria,Louloudi, Maria,Raptopoulou, Catherine P.,Psycharis, Vassilis,Milios, Constantinos J.,Plakatouras, John C.
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p. 3638 - 3644
(2015/04/27)
-
- Dendritic fluoroalcohols as catalysts for alkene epoxidation with hydrogen peroxide
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Cooperativity is the key for mild catalytic epoxidation: The immobilization of fluoroalcohols on dendritic polyglycerol (by "click chemistry") provides organocatalysts that can form multiple hydrogen bonds. The epoxidation of alkenes with aqueous hydrogen peroxide proceeds efficiently in the presence of dendritic fluoroalcohol catalysts. The supported catalysts can be separated by membrane filtration and reused. Copyright
- Berkessel, Albrecht,Kraemer, Jan,Mummy, Florian,Neudoerfl, Joerg-M.,Haag, Rainer
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p. 739 - 743
(2013/02/23)
-
- Facile synthesis of chiral 1,2-chlorohydrins via the ring-opening of meso-epoxides catalyzed by chiral phosphine oxides
-
The facile synthesis of chiral 1,2-chlorohydrins via the enantioselective ring-opening of meso-epoxides with silicon tetrachloride in the presence of a chiral phosphine oxide was accomplished. The chiral 1,2-chlorohydrins were also obtained from the corresponding cis-alkenes in one-pot without significant loss in the selectivity, thereby permitting easy access to the 1,2-chlorohydrins from cis-alkenes with good yields and enantioselectivities.
- Kotani, Shunsuke,Furusho, Haruka,Sugiura, Masaharu,Nakajima, Makoto
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p. 3075 - 3081
(2013/03/28)
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- Iron(III) chloride-benzotriazole adducts with trigonal bipyramidal geometry: Spectroscopic, structural and catalytic studies
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The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl 3(Mebta)2] (2), [FeCl3(5,6Me 2btaH)2] (3) and [FeCl3(5ClbtaH) 2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1-4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mo?ssbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the "green" H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail.
- Anastasiadis, Nikolaos C.,Bilis, George,Plakatouras, John C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Beavers, Christine,Teat, Simon J.,Louloudi, Maria,Perlepes, Spyros P.
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p. 189 - 202
(2013/10/08)
-
- Covalent attachment of a biomimetic Ru-(terpy)(bpy) complex on silica surface: Catalytic potential
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The Ru-containing modified silica [RuII(terpy)(4′Mebpy/ 4CONH(CH2)3SiO3/2)Cl]+ m·zSiO2 has been prepared by covalent attachment on silica surface of biomimetic [RuII(terpy)(4-CO2H- 4′-Mebpy)Cl]+ complex through the formation of a pseudo-peptide bond. The catalytic ability of bio-derived silica for alkene oxidation with HOOtBu has been evaluated exhibiting significant efficiency and, in some cases, showing increased activity compared vs. the corresponding 'net' [RuII(terpy)(4-CO2H-4′-Mebpy)Cl]+ complex. The data supported that the covalently attached ruthenium complex preserves the catalytic behaviour of the 'net' ruthenium complex indicating that the presented grafting process was successful.
- Papafotiou,Karidi,Garoufis,Louloudi
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p. 634 - 638
(2013/08/14)
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- Microkinetic modeling of cis-cyclooctene oxidation on heterogeneous Mn-tmtacn complexes
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Experiments and microkinetic modeling were used to investigate the reaction mechanism of cis-cyclooctene oxidation with H2O2 on heterogeneous manganese 1,4,7-trimethyl-1,4,7-triazacyclononane (Mn-tmtacn) catalysts. A mechanism based on literature reports and model discrimination was identified that captured experimental data well, including data at reaction conditions that were not used for parameter estimation. H2O 2 activation on the heterogeneous catalytic complex was identified as the rate-determining step (RDS), and a simple analytical rate expression was derived using the RDS and the pseudo-steady-state approximation for all intermediates. Predicted reaction orders for cis-cyclooctene, water, H 2O2, catalyst, and diol and epoxide products are also consistent with experimental observations and can be rationalized according to the derived rate expression. In addition, the ratio of productive to unproductive H2O2 use is analyzed, and catalyst deactivation is found to be an important step in the reaction mechanism that is highly sensitive to temperature.
- Bjorkman, Kathryn R.,Schoenfeldt, Nicholas J.,Notestein, Justin M.,Broadbelt, Linda J.
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body text
p. 17 - 25
(2012/08/14)
-
- An efficient recyclable peroxometalate-based polymer-immobilised ionic liquid phase (PIILP) catalyst for hydrogen peroxide-mediated oxidation
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A linear cation-decorated polymeric support with tuneable surface properties and microstructure has been prepared by ring-opening metathesis polymerisation (ROMP) of a pyrrolidinium-functionalised norbornene-based monomer with cyclooctene. The derived peroxophosphotungstate-based polymer-immobilised ionic liquid phase (PIILP) catalyst is an efficient and recyclable system for the epoxidation of allylic alcohols and alkenes, with only a minor reduction in performance on successive cycles.
- Doherty, Simon,Knight, Julian G.,Ellison, Jack R.,Weekes, David,Harrington, Ross W.,Hardacre, Christopher,Manyar, Haresh
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supporting information; experimental part
p. 925 - 929
(2012/06/18)
-
- Synthesis, characterization and crystal structures of new bidentate Schiff base ligand and its vanadium(IV) complex: The catalytic activity of vanadyl complex in epoxidation of alkenes
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The Schiff base ligand N-salicylidin-2-bromoethylimine (L) and its vanadium(IV) complex, VOL2 (1), were synthesized and characterized by using X-ray, CHN, 1H NMR and FT-IR methods. X-ray analysis shows the Schiff base ligand L acts as a bidentate (O, N) chelating ligand and coordinates via imine nitrogen and phenolato oxygen atoms to the V(IV) center. The coordination geometry around the V(IV) center in 1 is approximately square pyramidal, as indicated by the unequal metal-ligand bond distances and angles, with the basal plane formed by the N2O2 donors of the two bidentate Schiff base ligands, the two phenolato O atoms and the two imine N atoms are in the trans position. The coordination sphere of the V(IV) is completed by one oxygen atom in apical position. In the Schiff base ligand, L, there are some classical intramolecular O1-H1...N1 and non-classical intermolecular C9-H9b...O1 hydrogen bonds, while in 1, there are two non-classical intermolecular C7-H7...O3 and C8-H8b...O3 hydrogen bonds. The catalytic activity of 1 in epoxidation of cyclooctene was investigated in different conditions to obtain optimum conditions. The effects of solvent, oxidant, catalyst concentration and alkene/oxidant ratio were studied and the results showed that in CCl4 in the presence of tert-butylhydroperoxide in 1:3 alkene/oxidant ratio, high epoxide yield was obtained. The epoxidation of alkenes was also carried out in optimized conditions that high catalytic activity and selectivity were obtained.
- Grivani, Gholamhossein,Khalaji, Aliakbar Dehno,Tahmasebi, Vida,Gotoh, Kazuma,Ishida, Hiroyuki
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experimental part
p. 265 - 271
(2012/03/09)
-
- Green and selective oxidation reactions catalyzed by kaolinite covalently grafted with Fe(III) pyridine-carboxylate complexes
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The immobilization of Fe(III) picolinate and Fe(III) dipicolinate complexes on kaolinite furnished heterogeneous catalysts, whose catalytic activity was evaluated. The precursor materials were kaolinite grafted with picolinic (Ka-pa) and dipicolinic (Ka-dpa) acids obtained by melting of the pyridine carboxylic acids. To obtain the catalysts Fe(Ka-pa)-n and Fe(Ka-dpa)-n (n = 1, 2, or 3 is the ligand/Fe ratio), the precursors were suspended in Fe3+ solutions with cation/ligand ratios of 1:1, 1:2, or 1:3. The resulting materials were characterized by thermal analyses (simultaneous TG/DTA), X-ray diffraction, UV/vis and infrared spectroscopies, and transmission electron microscopy. The grafted complexes were employed as heterogeneous catalysts in the epoxidation of cis-cyclooctene to cis-cyclooctenoxide and in the oxidation of cyclohexane to cyclohexanol and cyclohexanone at ambient temperature and pressure. Hydrogen peroxide was used as oxygen donor at a catalyst/oxidant/substrate molar ratio of 1:300:100. Fe(Ka-pa)-n catalysts were very efficient for cis-cyclooctene epoxidation (38% conversion). For cyclohexane oxidation, Fe(Ka-dpa)-n was 100% selective for cyclohexanone formation, with substrate conversion of 14%. This last series of catalysts was also very effective in the Baeyer-Villiger reaction, with 60% substrate conversion and 100% selectivity for ξ-caprolactone. After reuse (5 times), the catalysts still led to high substrate conversion.
- De Faria, Emerson H.,Ricci, Gustavo P.,Mar?al, Liziane,Nassar, Eduardo J.,Vicente, Miguel A.,Trujillano, Raquel,Gil, Antonio,Korili, Sophia A.,Ciuffi, Katia J.,Calefi, Paulo S.
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experimental part
p. 135 - 149
(2012/08/08)
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- A heterogenized vanadium oxo-aroylhydrazone catalyst for efficient and selective oxidation of hydrocarbons with hydrogen peroxide
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A hydrazone Schiff base ligand derived from salicylaldehyde and benzhydrazide has been synthesized and reacted with vanadium(IV) leading to the corresponding vanadium(V) complex. The complex has been anchored on the surface of functionalized silica gel by N,O-coordination to the covalently Si-O bound modified salicylaldiminato ligand. The supported complex has been evaluated as a catalyst for hydrocarbon oxidation with hydrogen peroxide in acetonitrile. The heterogeneous system proved to be an efficient catalyst and was able to activate hydrogen peroxide toward the oxidation of alkenes, alkanes, benzene, and alkylaromatic compounds with more than 2,500 h-1 activity. Springer Science+Business Media B.V. 2011.
- Monfared, Hassan Hosseini,Abbasi, Vahideh,Rezaei, Adineh,Ghorbanloo, Massomeh,Aghaei, Alireza
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experimental part
p. 85 - 92
(2012/08/28)
-
- Oxidation reactions using polymer-supported 2-benzenesulfonyl-3-(4- nitrophenyl)oxaziridine
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A thermally stable polymer-supported oxidant has been developed. Polymer-supported 2-benzenesulfonyl-3-(4-nitrophenyl)oxaziridine was applied to microwave-assisted reactions that occurred at high temperatures and was shown to oxidize alkenes, silyl enol ethers, and pyridines to the corresponding epoxides and pyridine N-oxides in excellent to good yields and with much shorter reaction times. It also enabled tetrahydrobenzimidazoles to be oxidatively rearranged to spiro fused 5-imidazolones in a more efficient manner. Recycling of the polymer-supported oxidant is also possible with minimal loss of activity after several reoxidations.
- Susanto, Woen,Lam, Yulin
-
experimental part
p. 8353 - 8359
(2011/11/12)
-
- Iron-catalyzed epoxidation of olefins using hydrogen peroxide
-
A practical method of olefin epoxidation was developed by combining FeCl3·6H2O and 1-methylimidazole in acetone using H2O2 as the terminal oxidant. This system showed very good reactivity toward epoxidation of both terminal and substituted alkenes. The use of tridentate and tetradentate amine-bis(phenolate) ligands as additives was also examined. Modest improvement in selectivity was achieved if a bulky tridentate ligand was used. Generally, however, the simple catalyst system involving ferric chloride, 1-methylimidazole and dilute H2O 2 in acetone proved most successful in achieving good to excellent yields of epoxide products for a number of substrates, including aromatic and aliphatic alkenes.
- Hasan, Kamrul,Brown, Nicole,Kozak, Christopher M.
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experimental part
p. 1230 - 1237
(2011/06/27)
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- CuO nanoclusters coated with mesoporous SiO2 as highly active and stable catalysts for olefin epoxidation
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A one-pot solvothermal synthetic method to prepare uniform CuO colloidal nanocrystal clusters (CNCs) with sizes of approximately 60 nm was developed. To enhance their stabilities, the CuO CNCs were coated with mesoporous SiO 2 shells to form CuO CNCs@meso-SiO2 nanocomposites. The CuO CNCs as well as the CuO CNCs@meso-SiO2 composite catalyst were characterized by transmission electron microscopy, small-angle X-ray diffraction and N2 adsorption-desorption methods. These results indicate that the SiO2 shells have winding mesoporous channels with an average size of 3.7 nm, which are very favorable for mass transfer and catalytic reactions. This nanocomposite catalyst exhibited excellent activity and stability in olefin epoxidation reactions. The structure of the composite catalyst remained intact after eight consecutive runs, while pure CuO CNCs severely aggregated after only 1 run. The Royal Society of Chemistry.
- Chen, Chaoqiu,Qu, Jin,Cao, Changyan,Niu, Fang,Song, Weiguo
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scheme or table
p. 5774 - 5779
(2011/11/30)
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- A biomimetic tris-imidazole/Mn(II) system for homogeneous catalytic epoxidation of olefins with H2O2
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A biomimetic tris-imidazole ligand, herein called L3imid, has been synthesized. The complexes formed by its association with Mn(II) have been evaluated for catalytic alkene epoxidation with H2O2. The catalytic efficiency of Mn(II)/L3imid system was shown to be switched on by ammonium acetate, with remarkable effectiveness and selectivity towards epoxides. The incorporation of the biomimetic ligand L3imid which combines structural features as Schiff base imine-groups and imidazole rings is considered to be related with the enhanced catalytic activity of the Mn(II)/L3imid system.
- Stamatis, Ag.,Vartzouma, Ch.,Louloudi
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experimental part
p. 475 - 479
(2011/12/16)
-
- A heterogeneous, selective oxidation catalyst based on Mn triazacyclononane grafted under reaction conditions
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A unique method has been developed to synthesize an active heterogeneous oxidation catalyst by the in situ grafting of a 1,4,7-trimethyl-1,4,7- triazacyclononane manganese complex on carboxylic acid-functionalized supports serving dual roles as surface tether and necessary co-catalyst, massively increasing total turnovers as compared to the homogeneous analog.
- Schoenfeldt, Nicholas J.,Korinda, Andrew W.,Notestein, Justin M.
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supporting information; experimental part
p. 1640 - 1642
(2010/07/03)
-
- Cp* iridium complexes give catalytic alkane hydroxylation with retention of stereochemistry
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A series of Cp Ir complexes can catalyze C-H oxidation, with ceric ammonium nitrate as the terminal oxidant and water as the source of oxygen. Remarkably the hydroxylation of cis-decalin and 1,4-dimethylcyclohexane proceeds with retention of stereochemistry. With H2O18, cis-decalin oxidation gave 18O incorporation into the product cis-decalol.
- Zhou, Meng,Schley, Nathan D.,Crabtree, Robert H.
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supporting information; scheme or table
p. 12550 - 12551
(2010/11/16)
-
- Coordination compounds from the planar tridentate schiff-base ligand 2-methoxy-6-((quinolin-8-ylimino)methyl)phenol (mqmpH) with several transition metal ions: Use of [FeIII(mqmp)(CH3OH)Cl2] in the catalytic oxidation of alkanes and alkenes
-
Four coordination compounds were synthesized in high yields from different transition metal ions (FeIII, CoII, and CuII) and an in situ generated Schiff-base ligand, i.e. 2-methoxy-6-((quinolin-8- ylimino) methyl)phenol (mqmpH). The compounds were characterized by single-crystal X-ray diffraction, ESIMS, IR spectroscopy, and ligand-field spectroscopy. The iron(III) complex is an efficient catalyst for the oxidation of alkanes and alkenes, under relatively mild conditions and with dihydrogen peroxide as terminal oxidant.
- Nayak, Sanjit,Gamez, Patrick,Kozlev?ar, Bojan,Pevec, Andrej,Roubeau, Olivier,Dehnen, Stefanie,Reedijk, Jan
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scheme or table
p. 2291 - 2296
(2010/09/06)
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- Photocatalytic aerobic oxidation by a bis-porphyrin-ruthenium(IV) μ-Oxo dimer: Observation of a putative porphyrin-ruthenium(V)-oxo intermediate
-
The title complexes catalyze the aerobic oxidations of hydrocarbons using visible light and atmospheric oxygen as oxygen source in sequences employing photodisproportionation reactions. The putative oxidants, ruthenium(V)-oxo porphyrin species, can be detected and studied in real time via laser flash photolysis methods.
- Vanover, Eric,Huang, Yan,Xu, Libin,Newcomb, Martin,Zhang, Rui
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supporting information; experimental part
p. 2246 - 2249
(2010/08/20)
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- Highly selective olefin epoxidation with the bicarbonate activation of hydrogen peroxide in the presence of manganese(III) meso-tetraphenylporphyrin complex: Optimization of effective parameters using the Taguchi method
-
A MnIII-porphyrin-based catalytic system was explored for olefin epoxidations under mild reaction conditions using sodium bicarbonate-hydrogen peroxide as an oxidant. The Mn(TPP)OAc/imidazol/NaHCO3 system efficiently catalyzed the epoxidation of olefins with H2O2. Cyclic olefins were transformed in excellent yield (80-100%) and selectivity (87-100%), the obtained selectivity and yields being much better than those observed in the absence of bicarbonate. In the presence of an excess of substrate, the turnover number 4286 was obtained with the Mn(TPP)OAc/Im/NaHCO3/H2O2 system after 2 h. The bicarbonate-activated oxidation system is a simple, inexpensive, and relatively nontoxic alternative to other oxidants and peroxyacids, and it can be used in a variety of oxidations where a mild, neutral pH oxidant is required. Due to the various factors, such as solvent, reaction temperature, stoichiometric ratio of imidazole/NaHCO3/H2O2, influencing the oxidation of olefins, the Taguchi method of system optimization was used to determine the percent of contribution (%P) of each factor. It was found that the solvent had the most influence on the oxidation (30.051%) and the imidazole amount stood in second place (22.286%).
- Monfared, Hassan Hosseini,Aghapoor, Vahideh,Ghorbanloo, Massomeh,Mayer, Peter
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experimental part
p. 209 - 216
(2011/02/16)
-
- Synthesis, crystal structure, and catalytic properties of novel dioxidomolybdenum(VI) complexes with tridentate schiff base ligands in the biomimetic and highly selective oxygenation of alkenes and sulfides
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Four novel dioxidomolybdenum(VI) complexes [MoO2(L x)(CH3OH)] have been synthesized, using 2[(E)-(2-hydroxy-2-phenylethylimino)methyl]phenol derivatives as tridentate ONO donor Schiff base ligands (H2Lx) and MoO 2(acac)2. A monoclinic space group was determined by X-ray crystallography from single-crystal data of a sample of these new complexes. The epoxidation of alkenes by using tert-butyl hydroperoxide and oxidation of sulfides to sulfoxides by urea hydrogen peroxide were efficiently enhanced with excellent selectivity under the catalytic influence these new MoVI complexes. The high efficiency and relative stability of the catalysts have been observed, by turnover numbers and UV/Vis investigations. The electron-poor and bulky ligands promoted the effectiveness of the catalysts. 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
- Rezaeifard, Abdolreza,Sheikhshoaie, Iran,Monadi, Maz,Stoeckli-Evans, Helen
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experimental part
p. 799 - 806
(2010/07/04)
-
- Molybdenum(VI) amino triphenolate complexes as catalysts for sulfoxidation, epoxidation and haloperoxidation
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Two molybdenum(VI) complexes bearing a C3 symmetrical amino tris-tert-butylphenolate ligand have proved to be air- and water-tolerant catalysts that efficiently catalyse, in high yields and selectivity, the oxidation of sulfides, olefins and halides. In particular high turnover frequencies and turnover numbers (TOF and TON) have been obtained for the cyclooctene epoxidation (catalyst loading down to 0.05%, TONs up to 88,000 and TOFs up to 7500h-1). Copyright
- Romano, Francesco,Linden, Anthony,Mba, Miriam,Zonta, Cristiano,Licini, Giulia
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experimental part
p. 2937 - 2942
(2011/01/05)
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- The catalytic function of SiO2-immobilized Mn(II)-complexes for alkene epoxidation with H2O2
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Two symmetrical acetylacetone-based Schiff bases were immobilized on a silica surface by grafting and sol-gel procedure. The corresponding supported manganese complexes were prepared and evaluated as heterogeneous catalysts for alkene epoxidation with H2O2. These heterogeneous catalysts show remarkable effectiveness and selectivity towards epoxide formation in the presence of ammonium acetate. Moreover, the developed heterogeneous catalysts preserve the coordination and catalytic properties of the active-homogeneous manganese catalysts for alkene epoxidation vs. the competitive H2O2 dismutation. EPR spectroscopy shows that in heterogeneous manganese catalysts the Mn2+ centers are in a flexible, non-tight, coordination environment, as in the corresponding homogeneous manganese catalysts. However, after a first use of the heterogeneous catalysts, the Mn centers are detached from the ligand and are randomly dispersed on the SiO2 surface. This is responsible for the loss of catalytic activity.
- Stamatis,Giasafaki,Christoforidis,Deligiannakis,Louloudi
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scheme or table
p. 58 - 65
(2010/06/20)
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- Photooxygenation of alkenes by molecular oxygen in the presence of porphyrins and chlorin sensitizers under visible light irradiation
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Photooxidation of alkenes by molecular oxygen and visible light in the presence of tetraphenylporphyrin (H2TPP), tetramesitylporphyrin (H2TMP), tetrakis pentafluorophenylporphyrin (H2TPFPP) and tetrakis(2,3-dimetoxyphenyl)porphyrin T(2,3-OMeP)P and metalloporphyrins such as ClFeTPP, ClMnTMP, ClMnTPP, ClMnTPFPP, ClCoTPP and ZnTPP has been performed. Photooxidation of alkenes with tetraphenylchlorin (H2TPC) as the sensitizer with visible light has also been studied. The conversion rates for alkene oxidation were in the order of free-base porphyrins > chlorin > metalloporphyrins. In the presence of NaN3/Na2SO 3 the yield of oxidation products and conversion percentage is considerably reduced, confirming involvement of 1O2 in the mechanism.
- Hajimohammadi, Mahdi,Safari, Nasser
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experimental part
p. 639 - 645
(2011/10/04)
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