- 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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- 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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- 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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- 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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- 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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- 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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- 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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- Synthesis, characterization, and catalytic oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)
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Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylened
- Singh, Vijay Kumar,Maurya, Abhishek,Kesharwani, Neha,Kachhap, Payal,Kumari, Sweta,Mahato, Arun Kumar,Mishra, Vivek Kumar,Haldar, Chanchal
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p. 520 - 541
(2018/02/26)
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- Synthesis of a pair of homochiral manganese-based coordination polymers as stable catalyst for the selective oxidation of cis-cyclooctene
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A pair of homochiral manganese-based coordination polymers [Mn(H2O)2(bpy)(L-DBTA)] (L-1) and [Mn(H2O)2(bpy)(D-DBTA)](D-1): Syntheses, crystal structures and catalytic properties for the selective oxidation of cis-cyclooctene. The homochiral manganese-based 3D supermolecule framework exhibits high catalytic activity (38.85% conversion based on cis-cyclooctene and 76.13% selectivity for epoxycyclooctane) and stability for selective oxidation of cis-cyclooctene in the absence of solvent using TBHP as radical initiator and oxygen (in the air) as oxidant at 80 °C.
- Zhang, Guangju,Shi, Yang,Wei, Ying,Zhang, Qingguo,Zhang, Yanping,Cai, Kedi,Xiu, Siqi
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- Photochirogenic nanosponges: phase-controlled enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by pyromellitate-crosslinked linear maltodextrin
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Linear maltodextrin (LM) was cross-linked by pyromellitic dianhydride to afford LM polymers of different cross-linking degrees. When soaked in water, these cross-linked LM polymers (nanosponges (NSs)), evolved into several phases from sol to suspension, then to flowing gel, and finally to rigid gel with an increase in their content. Enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to chiral (E)-isomer (1E), which was employed as a benchmark reaction to quantitatively assess the environmental-to-molecular chirality transfer process, was performed in aqueous media containing these pyromellitate-crosslinked LM-NSs in different phases. The enantiomeric excess (ee) of 1E obtained was relatively insensitive to the phases at least up to the flowing gel phase, but became highly sensitive in the rigid gel phase, exhibiting an abrupt drop in the early rigid gel phase followed by a rapid recovery in the late rigid gel phase. A comparison with the phase-dependent ee profiles previously reported for similar pyromellitate-crosslinked cyclodextrin (CD)- and cyclic nigerosylnigerose (CNN)-NSs revealed that the chiral void space created around the pyromellitate linker in NS is responsible for the dramatic changes in ee in the rigid gel phase, whereas the inherent host cavity in CD/CNN plays only limited roles in the supramolecular photochirogenesis mediated by the sensitizer-crosslinked NSs. The latter insight allows us to further expand the applicable range of the present concept and methodology by employing a much wider variety of oligosaccharides as well as substrates and sensitizing cross-linkers.
- Liang, Wenting,Zhao, Meiling,Wei, Xueqin,Yan, Zhiqiang,Wu, Wanhua,Caldera, Fabrizio,Trotta, Francesco,Inoue, Yoshihisa,Su, Dan,Zhong, Zhihui,Yang, Cheng
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p. 17184 - 17192
(2017/03/30)
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- Two kinds of cobalt–based coordination polymers with excellent catalytic ability for the selective oxidation of cis-cyclooctene
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Two kinds of cobalt–based coordination polymers {[Co(dsd)(H2O)4]·4,4′-bpy}(1) and {[Co(dsd)(H2O)4]·H2O} (2) with the chain structure possess excellent catalytic ability for the selective oxidation of
- Zhang, Guangju,Shi, Yang,Wei, Ying,Zhang, Qingguo,Cai, Kedi
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p. 112 - 117
(2017/10/13)
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- Selective oxidation of olefins with aqueous hydrogen peroxide over phosphomolybdic acid functionalized knitting aryl network polymer
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A phosphomolybdic acid (PMA)-based heterogeneous catalyst, denoted as PMA/KAP, was prepared by immobilizing PMA onto a knitting aryl network polymer (KAP) based on triphenylphosphine (PPh3). The catalytic property of PMA/KAP was investigated for the selective oxidation of olefins with aqueous hydrogen peroxide (H2O2) as oxidant. When using ethyl acetate (EAC) as reaction medium, PMA/KAP performs higher activity and selectivity to epoxide for a variety of olefins, and it can be reused for several times without obvious loss of activity. When the reaction was carried out in acetonitrile (AN) medium, deactivation of PMA/KAP catalyst can be observed immediately. A variety of characterization results suggest that the degradation of PMA unit to (PO4[MoO(O2)2]4)3- occurs easily when the PMA/KAP catalyst is operated in H2O2/AN system, while such degradation behavior could be significantly inhibited when the catalyst is used in the system of H2O2/EAC. We proposed that the neighbouring P-containing ligands dispersed in the framework of KAP can produce a steric pocket with low electron density, which can promote the formation of multi-weak coordination interaction between PMA unit and several P ligands. Such multi-weak interaction can inhibit the degradation of PMA to (PO4[MoO(O2)2]4)3-, thus avoiding the leaching of active species from the KAP support, and resulting in the formation of relatively stable heterogeneous PMA supported catalyst for olefin epoxidation with H2O2 in the media of EAC.
- Song, Xiaojing,Zhu, Wanchun,Yan, Yan,Gao, Hongcheng,Gao, Wenxiu,Zhang, Wenxiang,Jia, Mingjun
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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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p. 36384 - 36393
(2016/05/24)
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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p. 2043 - 2046
(2016/02/05)
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- Design and preparation of a polymer resin-supported organoselenium catalyst with industrial potential
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Hexavalent Se? Yes! Selenium on polymers exhibits quite different properties compared to that in small molecules. Hexavalent Se, rare in organoselenium chemistry, was found to be the major species on polymers. The high-valent Se species on recyclable polymer resins could quickly catalyze the oxidation reaction of cyclohexene with H2O2 in water to produce industrially important intermediate trans-1,2-cyclohexanediol in almost quantitative yield. In the catalytic cycle, high valent Se species were reduced to divalent Se, a highly activated species that could be re-oxidized by air so that no excess H2O2 was required for the reaction. The results were superior to those of reactions catalyzed by small molecules, for which excess H2O2, long reaction time or expensive CF3-activated catalysts and environmentally unfriendly MeCN solvent were required.
- Wang, Yuguang,Yu, Lihua,Zhu, Bingchun,Yu, Lei
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supporting information
p. 10828 - 10833
(2016/07/21)
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- Heterometallic Metal-Organic Frameworks That Catalyze Two Different Reactions Sequentially
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A series of copper- and alkaline-earth-metal-based multidimensional metal-organic frameworks, {[CuMg(pdc)2(H2O)4]·2H2O}n (1), [CuCa(pdc)2]n (2), [CuSr(pdc)2(H2O)3]n (3), and {[Cuba(pdc)2(H2O)5]·H2O}n (4), where H2Pdc = pyridine-2,5-dicarboxylic acid, were hydrothermally synthesized and characterized. Two different metals act as the active center to catalyze two kinds of reactions, viz., olefin to its epoxide followed by epoxide ring opening to afford the corresponding vicinal diol in a sequential manner.
- Saha, Debraj,Hazra, Dipak K.,Maity, Tanmoy,Koner, Subratanath
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supporting information
p. 5729 - 5731
(2016/07/06)
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- Oxidation of olefins with H2O2 catalyzed by gallium(III) nitrate and aluminum(III) nitrate in solution
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Soluble gallium and aluminum nitrates (simple salts of non-transition metals) are good catalysts for the epoxidation of olefins (cyclooctene, dec-1-ene) including terpenes (carvone, limonene) with hydrogen peroxide in ethyl acetate or tetrahydrofurane (THF). Typically, the gallium salt is more efficient in comparison with the aluminum derivative. Products are formed in yields up to 93%, turnover numbers (TONs) attained 40. Addition of trifluoroacetic acid or pyrazine-2-carboxylic acid (PCA) accelerates the reaction and improves the yield. In striking contrast, added 2,2′-bipyridine or phenanthroline dramatically inhibit the oxidation.
- Mandelli, Dalmo,Kozlov, Yuriy N.,da Silva, Cezar A.R.,Carvalho, Wagner A.,Pescarmona, Paolo P.,Cella, Daniele de A.,de Paiva, Polyana T.,Shul'pin, Georgiy B.
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p. 216 - 220
(2016/09/19)
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- Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
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We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
- Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
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p. 1972 - 1978
(2015/02/19)
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- Oxidation of cyclooctene to suberic acid using perrhenate-containing composite ionic liquids as green catalysts
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A series of quaternary ammonium perrhenate/3-hexyl-1-methyl-imidazolium hydrogen sulfate ([Hmim]HSO4) composite ionic liquids has been prepared. For the first time, the composite ionic liquids are used both as catalyst and solvent in oxidation of cyclooctene to suberic acid in the presence of hydrogen peroxide as a green oxidant. It was found that organic perrhenate salts play the important role in improving the selectivity of cyclooctene oxidation to suberic acid. The yield of suberic acid under the mild conditions is from good to high.
- Wang,Zhou,Yuan,Fu,Zang
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p. 2378 - 2385
(2015/11/24)
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- Redox-inactive metal ions promoted the catalytic reactivity of non-heme manganese complexes towards oxygen atom transfer
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Redox-inactive metal ions can modulate the reactivity of redox-active metal ions in a variety of biological and chemical oxidations. Many synthetic models have been developed to help address the elusive roles of these redox-inactive metal ions. Using a non-heme manganese(ii) complex as the model, the influence of redox-inactive metal ions as a Lewis acid on its catalytic efficiency in oxygen atom transfer was investigated. In the absence of redox-inactive metal ions, the manganese(ii) catalyst is very sluggish, for example, in cyclooctene epoxidation, providing only 9.9% conversion with 4.1% yield of epoxide. However, addition of 2 equiv. of Al3+ to the manganese(ii) catalyst sharply improves the epoxidation, providing up to 97.8% conversion with 91.4% yield of epoxide. EPR studies of the manganese(ii) catalyst in the presence of an oxidant reveal a 16-line hyperfine structure centered at g = 2.0, clearly indicating the formation of a mixed valent di-μ-oxo-bridged diamond core, MnIII-(μ-O)2-MnIV. The presence of a Lewis acid like Al3+ causes the dissociation of this diamond MnIII-(μ-O)2-MnIV core to form monomeric manganese(iv) species which is responsible for improved epoxidation efficiency. This promotional effect has also been observed in other manganese complexes bearing various non-heme ligands. The findings presented here have provided a promising strategy to explore the catalytic reactivity of some di-μ-oxo-bridged complexes by adding non-redox metal ions to in situ dissociate those dimeric cores and may also provide clues to understand the mechanism of methane monooxygenase which has a similar diiron diamond core as the intermediate.
- Choe, Cholho,Yang, Ling,Lv, Zhanao,Mo, Wanling,Chen, Zhuqi,Li, Guangxin,Yin, Guochuan
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p. 9182 - 9192
(2015/05/20)
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- Novel CuII-MII-CuII (M = Cu or Ni) trinuclear and [Na i 2 Cu II 6] hexanuclear complexes assembled by bi-compartmental ligands: Syntheses, structures, magnetic and catalytic studies
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In the present work, two compartmental ligands H2L1 and H2L2 were in situ generated during the syntheses of new trinuclear complexes, [Cu2Ni(L1)(2,2′-bpy)2(NO3)2][ClO4]2 (5), [Cu3(L2)(NO3)2][ClO4]2 (6), and [Cu3(L2)(NCS)2(NO3)]+ that co-crystallize in 7 with a [Cu6(L2)2Na2(NO3)6(NCS)4] unit to give the final molecular formula [Cu6(L2)2Na2(NO3)6(NCS)4][Cu3(L2)(NCS)2(NO3)]2(NO3)2·5H2O (7). The magnetic property studies of 5-7 revealed weak CuII-CuII ferromagnetic interactions in compound 6 (JCu-Cu/kB = +1.4(1) K) and 7 (JCu-Cu/kB = +1.6) while in intranuclear CuII-NiII-CuII compound 5, the magnetic coupling between two CuII ions is switched off by the diamagnetic square planar NiII bridge. The catalytic epoxidation of two olefins, namely styrene and cyclooctene, by tert-BuOOH (TBHP) was also explored in the presence of a catalytic amount of 5, 6 or 7 in MeCN. For styrene oxidation, 5 exhibited ~57% styrene epoxide selectively (conversion ~37%) with a TON of about 925 along with benzaldehyde (~43%), whereas 6 exhibited conversion up to ~63% (TON ~ 1575) with a good selectivity towards epoxide (~71%). For compound 7, this conversion is more important (TON ~ 8108) probably due to the presence of more active sites involved in the epoxidation. The concerted path was found to be operative for styrene oxidation while a radical path was suggested for the oxidation of cyclooctene.
- Biswas, Surajit,Dutta, Arpan,Dolai, Malay,Bhowmick, Indrani,Rouzières, Mathieu,Clérac, Rodolphe,Panja, Anangamohan,Ali, Mahammad
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p. 9426 - 9438
(2015/06/16)
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- Synthesis, Crystal Structures, and Magnetic and Catalytic Studies on a Linear Trinuclear MnII3 Complex
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An almost linear (3(L)(N3)4]·2 H2O (1) of a decacoordinating N8O2 donor ligand, H2L, was synthesized and structurally characterized by means of single-crystal X-ray crystallography and mass spectrometry. All the MnII centers are in pseudo-octahedral geometry and wrapped by a single decacoordinating N8O2 donor ligand. The central manganese atom (Mn2) is connected to two terminal manganese (Mn1 and Mn3) atoms by two bridging phenolate O atoms and two bridging azide N atoms. Compound 1 is the first example of a linear trinuclear model to show pronounced epoxidation of olefins by tert-butylhydroperoxide (TBHP) with a turnover number (TON) greater than 950. Though epoxidation of olefins by m-chloroperbenzoic acid (m-CPBA) was found to be complete within 20 minutes of mixing, the conversion was not more than 40 % and corresponding alcohols were found to be major products, whereas with H2O2 as oxidant there was no visible catalytic epoxidation of olefins. Furthermore, the compound was characterized by temperature-dependent magnetic susceptibility measurements and a total spin ground state of St=15/2 was found.
- Dutta, Arpan,Biswas, Surajit,Escuer, Albert,Dolai, Malay,Ghosh, Subhadip,Ali, Mahammad
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p. 1440 - 1447
(2015/09/15)
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- En route to multicatalysis: Kinetic resolution of trans-cycloalkane-1,2- diols via oxidative esterification
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We demonstrate the application of a multicatalyst to the oxidation of a broad variety of aldehydes and subsequent enantioselective esterification of the incipient acids with (±)-trans-cycloalkane-1,2-diols. This reaction operates well with a multicatalyst bearing two independent catalytic moieties that provide monoprotected 1,2-diols in one pot.
- Hofmann, Christine,Schuler, Soeren M. M.,Wende, Raffael C.,Schreiner, Peter R.
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p. 1221 - 1223
(2014/01/17)
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- Single end to end azido bridged adduct of a tridentate schiff base copper(II) complex: Synthesis, structure, magnetism and catalytic studies
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Copper(II) azido complex [CuL(μ-1,3-N3)] n (1) of a NNO donor tridentate Schiff base (HL = 2-[1-(methylamino-ethylimino)-methyl]-phenol containing single end-to-end μ-1,3-azido bridged 1D infinite chain has been synthesized and characterized by elemental analysis, FT-IR spectroscopy. X-ray single crystal structure analysis reveals that in 1, the central copper(II) ion displays a distorted square pyramidal coordination geometry and are linked by single EE azide bridges forming chains running parallel to the crystallographic b axis. The magnetic interaction revealed that 1 is antiferromagnetic in nature (J = -19.5 (±0.2) cm-1). The catalytic activity of the complex is investigated in a series of solvents for the oxidation of olefins using tert-butyl-hydroperoxide as oxidant. The results showed highest selectivity for 1 in acetonitrile medium.
- Banerjee, Sourajit,Adhikary, Chandan,Rizzoli, Corrado,Pal, Rammohan
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p. 202 - 207
(2013/12/04)
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- Doped graphene as a metal-free carbocatalyst for the selective aerobic oxidation of benzylic hydrocarbons, cyclooctane and styrene
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Nitrogen (N)-, boron (B)-, and boron,nitrogen (B,N)-doped graphene (G) act as carbocatalysts, promoting the aerobic oxidation of the benzylic positions of aromatic hydrocarbons and cyclooctane to the corresponding alcohol/ketone mixture with more than 90 % selectivity. The most active material was the co-doped (B,N)G, which, in the absence of solvent and with a substrate/(B,N)G ratio of 200, achieved 50 % tetralin conversion in 24 h with a alcohol/ketone selectivity of 80 %. An FT-Raman spectroscopic study of a sample of (B,N)G heated at 100 °C in the presence of oxygen revealed new bands that disappeared upon evacuation and that have been attributed to hydroperoxide-like species formed on the G sheet based on the isotopic shift of the peak from 819 to 779 cm-1 when 18O2 was used as the oxidizing reagent. Furthermore, (B)G and (N)G exhibited high catalytic activity in the aerobic oxidation of styrene to benzaldehyde (BA) in 4 h. However, the product distribution changed over time and after 10 h a significant percentage of styrene oxide (SO) was observed under the same conditions. The use of doped G as catalyst appears to offer broad scope for the aerobic oxidation of benzylic compounds and styrene, for which low catalyst loading, mild reaction temperatures, and no additional solvents are required. Oxidation at graphene: Boron- and nitrogen-doped graphenes are excellent catalysts for promoting the oxidation of benzylic hydrocarbons, cyclooctane, and styrene with molecular oxygen at 0.5 wt % under atmospheric pressure and solvent-free conditions (see figure). Copyright
- Dhakshinamoorthy, Amarajothi,Primo, Ana,Concepcion, Patricia,Alvaro, Mercedes,Garcia, Hermenegildo
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p. 7547 - 7554
(2013/07/11)
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- Enantioselective biooxidation of racemic trans-cyclic vicinal diols: One-pot synthesis of both enantiopure (S,S)-cyclic vicinal diols and (R)-α-hydroxy ketones
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Highly regio- and enantioselective alcohol dehydrogenases BDHA (2,3-butanediol dehydrogenase from Bacillus subtilis BGSC1A1), CDDHPm (cyclic diol dehydrogenase from Pseudomonas medocina TA5), and CDDHRh (cyclic diol dehydrogenase from Rhodococcus sp. Moj-3449) were discovered for the oxidation of racemic trans-cyclic vicinal diols. Recombinant Escherichia coli expressing BDHA was engineered as an efficient whole-cell biocatalyst for the oxidation of (±)-1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,2-cycloheptane-diol, and 1,2-cyclooctanediol, respectively, to give the corresponding (R)-α-hydroxy ketones in >99% ee and (S,S)-cyclic diols in >99% ee at 50% conversion in one pot. Escherichia coli (BDHA-LDH) co-expressing lactate dehydrogenase (LDH) for intracellular regeneration of NAD+ catalyzed the regio- and enantioselective oxidation of (±)-1,2-dihydroxy-1,2,3,4- tetrahydronaphthalene to produce the corresponding (R)-α-hydroxy ketone in >99% ee and (S,S)-cyclic diol in 96% ee at 49% conversion. Preparative biotransformations were also demonstrated. Thus, a novel and useful method for the one-pot synthesis of both vicinal diols and α-hydroxy ketones in high ee was developed via high Copyright
- Zhang, Jiandong,Xu, Tingting,Li, Zhi
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supporting information
p. 3147 - 3153
(2013/12/04)
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- Enhanced rate and selectivity by carboxylate salt as a basic cocatalyst in chiral N-heterocyclic carbene-catalyzed asymmetric acylation of secondary alcohols
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The rate and enantioselectivity of chiral NHC-catalyzed asymmetric acylation of alcohols with an adjacent H-bond donor functionality are remarkably enhanced in the presence of a carboxylate cocatalyst. The degree of the enhancement is correlated with the basicity of the carboxylate. With a cocatalyst and a newly developed electron-deficient chiral NHC, kinetic resolution and desymmetrization of cyclic diols and amino alcohols were achieved with extremely high selectivity (up to s = 218 and 99% ee, respectively) at a low catalyst loading (0.5 mol %). This asymmetric acylation is characterized by a unique preference for alcohols over amines, which are not converted into amides under the reaction conditions.
- Kuwano, Satoru,Harada, Shingo,Kang, Bubwoong,Oriez, Raphael,Yamaoka, Yousuke,Takasu, Kiyosei,Yamada, Ken-Ichi
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supporting information
p. 11485 - 11488
(2013/09/02)
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- Mesostructured dihydroxy-functionalized guanidinium-based polyoxometalate with enhanced heterogeneous catalytic activity in epoxidation
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A mesostructured ionic liquid-polyoxometalate (IL-POM) hybrid has been prepared through designing a new dihydroxy-tethered guanidinium-based IL, N′′-(2,3-dihydroxypropyl)-N,N,N′,N′- tetramethylguanidinium chloride, to interact with Keggin-type POM phosphotungstic acid (H3PW) in a self-assembly process. Scanning electron microscopy and transmission electron microscopy showed its special coral-shaped micromorphology. Nitrogen sorption analysis indicated the formation of a porous structure with a moderate surface area of about 30 m2 g-1 and narrowly distributed pore size located in the mesoscale. Assessed in the cis-cyclooctene epoxidation with H2O2, the mesostructured hybrid exhibited superior heterogeneous catalytic activity and steady reusability, and the conversion was more than four times that of homogeneous H3PW itself, and more than 14 times that of the nonporous analogues. On the basis of the experimental results, a unique substrate-solvent-catalyst synergistic mechanism is proposed and discussed for understanding the dramatically enhanced catalytic performance. Copyright
- Chen, Guojian,Zhou, Yu,Zhao, Pingping,Long, Zhouyang,Wang, Jun
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p. 561 - 569
(2013/07/26)
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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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supporting information
p. 9444 - 9447
(2013/08/23)
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- A cobalt-based 3D porous framework with excellent catalytic ability for the selective oxidation of cis-cyclooctene
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A 3D porous framework [Co3(μ2-OH) 4(I)2]·2H2O (I = hypoxanthine) with two types of 1D channels possess excellent catalytic ability for the selective oxidation of cis-cyclooctene. The Royal Society of Chemistry 2013.
- Zhang, Guangju,Li, Hao,Zhao, Fangfang,Hu, Hailiang,Huang, Hui,Li, Haitao,Han, Xiao,Liu, Ruihua,Dong, Huan,Liu, Yang,Kang, Zhenhui
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supporting information
p. 9423 - 9427
(2013/08/23)
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- Fe(PyTACN)-catalyzed cis-dihydroxylation of olefins with hydrogen peroxide
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A family of iron complexes with general formula [Fe(II)( R,Y,XPyTACN)(CF3SO3)2], where R,Y,XPyTACN=1-[2′-(4-Y-6-X-pyridyl)methyl]-4,7-dialkyl-1,4, 7-triazacyclononane, X and Y refer to the groups at positions 4 and 6 of the pyridine, respectively, and R refers to the alkyl substitution at N-4 and N-7 of the triazacyclononane ring, are shown to be catalysts for efficient and selective alkene oxidation (epoxidation and cis-dihydroxylation) employing hydrogen peroxide as oxidant. Complex [Fe(II)(Me,Me,HPyTACN)(CF 3SO3)2] (7), was identified as the most efficient and selective cis-dihydroxylation catalyst among the family. The high activity of 7 allows the oxidation of alkenes to proceed rapidly (30 min) at room temperature and under conditions where the olefin is not used in large amounts but instead is the limiting reagent. In the presence of 3 mol% of 7, 2 equiv. of H2O2 as oxidant and 15 equiv. of water, in acetonitrile solution, alkenes are cis-dihydroxylated reaching yields that might be interesting for synthetic purposes. Competition experiments show that 7 exhibits preferential selectivity towards the oxidation of cis olefins over the trans analogues, and also affords better yields and high [syn-diol]/[epoxide] ratios when cis olefins are oxidized. For aliphatic substrates, reaction yields attained with the present system compare favourably with state of the art Fe-catalyzed cis-dihydroxylation systems, and it can be regarded as an attractive complement to the iron and manganese systems described recently and which show optimum activity against electron-deficient and aromatic olefins. Copyright
- Prat, Irene,Font, David,Company, Anna,Junge, Kathrin,Ribas, Xavi,Beller, Matthias,Costas, Miquel
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supporting information
p. 947 - 956
(2013/05/08)
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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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supporting information
p. 10380 - 10383
(2013/07/26)
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- Dinuclear CuII-CuII and CuI-Cu II complexes of a compartmental ligand - Syntheses, structures, magnetic, and catalytic studies
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Dinuclear CuII-CuII (1) and CuI-Cu II (2) complexes were derived from a new N4O2 donor compartmental ligand (H2L) by changing the nature of the Cu precursors used. Single-crystal X-ray diffraction studies revealed that the Cu1 site in 1 has octahedral geometry and is in the inner compartment of the ligand axially coordinated by two ClO4- anions, whereas the outer Cu2 ion has square-pyramidal geometry. In 2, there are two copper dinuclear complexes (A and B) in the asymmetric unit; the inner core is occupied by Cu1/Cu3 in the +2 oxidation state in a square-planar geometry. The Cu2/Cu4 ion occupies the outer sites and has distorted tetrahedral geometry with a +1 oxidation state. Complexes 1 and 2 were obtained simply by changing Cu(ClO 4)2 in 1 to Cu(ClO4)2 and Cu(bipy)(NO3)2 in 2; the bipyridyl (bipy) ligand induces the reduction of CuII to CuI, which is trapped in the CuI-CuII dinuclear product. The oxidation states of the metal ions were ascertained from charge-balance considerations as well as from bond valence sum (BVS) calculations. No signature of intervalence charge transfer (IVCT) was observed by spectroscopy (UV/Vis/NIR) as well as from the low-temperature magnetic studies. This might be because of the presence of two copper centers in two different geometries with a wide separation between them (ca. 3.27 A). For 1, the best fit of the χT vs. T data to the dimer model gives J/kB = -262(1) K and gav = 2.05(5), which indicates that there is a strong antiferromagnetic coupling between the two Cu atoms. In 2, the CuI center is diamagnetic and, thus, the remaining S = 1/2 CuII magnetic center follows a Curie law with g = 2.06(5). Under homogeneous conditions, both complexes showed catalytic epoxidation of cyclooctene, styrene, and norbornene to the corresponding epoxides with high selectivities and turnover numbers (TONs), which seem to be slightly better than the reported values for CuII Schiff base complexes. Dinuclear CuII-CuII (1) and CuI-CuII (2) complexes derived from a new N4O2 donor ligand (H 2L) are synthesized and characterized by single-crystal X-ray diffraction, UV/Vis spectroscopy, and magnetic measurements. In 1, there is strong antiferromagnetic coupling between the Cu atoms. In 2, the CuI ion is diamagnetic and the remaining S = 1/2 CuII magnetic center follows a Curie law with g = 2.06(5). Copyright
- Biswas, Surajit,Dutta, Arpan,Dolai, Malay,Bhowmick, Indrani,Rouzieres, Mathieu,Lee, Hon Man,Clerac, Rodolphe,Ali, Mahammad
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p. 4922 - 4930
(2013/10/21)
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- The effect of encapsulated Zn-POM on the catalytic activity of MIL-101 in the oxidation of alkenes with hydrogen peroxide
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Zinc monosubstituted Keggin heteropolyanion [PZnMo2W 9O39]5- was electrostatically bound to nanocages of MIL-101 polymer matrix. The Zn-POM@MIL-101 catalyst was characterized by XRD, N2 adsorption, atomic absorption (AAS), and FT-IR spectroscopic methods. The catalytic activity of the new composite material, Zn-POM@MIL-101, was assessed in the oxidation of alkenes using aqueous hydrogen peroxide as oxidant. Zn-POM@MIL-101/H2O2 catalytic system demonstrated good catalytic activity in the oxidation reactions. Zn-POM@MIL-101 was reusable for three catalytic cycles. While the MIL-101 matrix is an active catalyst in these oxidation reactions, the presence of Zn-POM significantly changed the selectivity and reaction times. Copyright
- Saedi, Zahra,Tangestaninejad, Shaharm,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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scheme or table
p. 463 - 473
(2012/05/20)
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- Enantiomerically enriched trans-diols from alkenes in one pot: A multicatalyst approach
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Multicatalysts consisting of non-natural oligopeptides with distinctly different catalytic moieties create molecular complexity in a multistep one-pot sequence starting from simple alkenes yielding highly enantiomerically enriched trans-diols. The Royal Society of Chemistry 2012.
- Hrdina, Radim,Mueller, Christian E.,Wende, Raffael C.,Wanka, Lukas,Schreiner, Peter R.
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p. 2498 - 2500
(2012/04/10)
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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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scheme or table
p. 961 - 965
(2012/02/16)
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- Olefin epoxidation with tert-BuOOH catalyzed by vanadium polyoxometalate immobilized on ionic liquid-modified MCM-41
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Preparation and characterization of vanadium-containing polyphosphomolybdates supported on ionic liquid-modified MCM-41, MCM-41-Im, are reported. The catalyst, [PVMo@MCM- 41-Im], was characterized by elemental analysis, X-ray diffraction, scanning electron microscopy and also FT-IR, and UV-Vis spectroscopic methods. This heterogeneous catalytic system was applied for efficient epoxidation of various olefins in the presence of tert-BuOOH in 1,2-dichloroethane under reflux. The catalyst can be reused several times without apparent loss of its catalytic performance.
- Hajian, Robabeh,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj,Khosropour, Ahmad Reza
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scheme or table
p. 4134 - 4144
(2012/03/26)
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- Efficient aerobic oxidation of hydrocarbons promoted by high-spin nonheme Fe(II) complexes without any reductant
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Fe(II)-tris(2-pyridylmethyl)amine complexes, Fe(II)-tpa, having different co-existing anions, [Fe(tpa)(MeCN)2](ClO4)2 (1), [Fe(tpa)(MeCN)2](CF3SO3)2 (2) and [Fe(tpa)Cl2] (3), were prepared. Effective magnetic moments (evaluated by the Evans method) revealed that while 1-3 in acetone and 3 in acetonitrile (MeCN) have a high-spin Fe(II) ion at 298 K, the Fe(II) ions of 1 and 2 are in the low-spin state in MeCN. The aerobic oxidation of 1-3 was monitored by UV-Vis spectral changes in acetone or MeCN under air at 298 K. Only the high-spin Fe(II)-tpa complexes were oxidized with rate constants of k obs = 0.1-1.3 h-1, while 1 and 2 were stable in MeCN. The aerobic oxidation of 1 or 2 in acetone was greatly accelerated in the presence of pure, peroxide-free cyclohexene (1000 equiv.) and yielded a large amount of oxidized products; 2-cyclohexe-1-ol (A) and 2-cyclohexene-1-one (K) (A + K: 23 940% yield based on Fe; A/K = 0.3), and cyclohexene oxide (810%). Besides cyclohexene, aerobic oxidation of norbornene, cyclooctene, ethylbenzene, and cumene proceeded in the presence of 1 in acetone at 348 K without any reductant. Essential factors in the reaction are high-spin Fe(II) ion and labile coordination sites, both of which are required to generate Fe(II)-superoxo species as active species for the H-atom abstraction of hydrocarbons.
- Furukawa, Shinya,Hitomi, Yutaka,Shishido, Tetsuya,Tanaka, Tsunehiro
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experimental part
p. 19 - 23
(2012/02/02)
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- Synthesis and characterization of supported heteropolymolybdate nanoparticles between silicate layers of Bentonite with enhanced catalytic activity for epoxidation of alkenes
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A new heterogeneous catalyst (PVMo/Bentonite) consisting of vanadium substituted heteropolymolybdate with Keggin-type structure Na 5[PV2Mo10O40]·14H 2O (PVMo) supported between silicate layers of bentonite has been synthesized by impregnation method and characterized using X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy and elemental analysis. X-ray diffraction and scanning electron microscopy analysis indicated that PVMo was finely dispersed into layers of bentonite as support. The PVMo/Bentonite used as an efficient heterogeneous catalyst for epoxidation of alkenes. Various cyclic and linear alkenes were oxidized into the corresponding epoxides in high yields and selectivity with 30% aqueous H2O 2. The catalyst was reused several times, without observable loss of activity and selectivity. The obtained results showed that the catalytic activity of the PVMo/Bentonite was higher than that of pure heteropolyanion (PVMo).
- Salavati, Hossein,Rasouli, Nahid
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scheme or table
p. 1853 - 1859
(2011/11/05)
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- Dioxomolybdenum(VI) complexes containing chiral oxazolines applied in alkenes epoxidation in ionic liquids: A highly diastereoselective catalyst
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New monometallic dioxomolybdenum complexes, 2 and 3, containing the bis(oxazoline) B and the oxazolinyl-pyridine C respectively, have been prepared and fully characterized both in solution and solid state, including the single-crystal X-ray diffraction analysis for 2, which represents the first structure of a Mo(VI) complex coordinated to a bis(oxazoline). These complexes, together with the bimetallic system 1, were used as catalytic precursors for alkenes epoxidation (cyclooctene, (R)-limonene, trans-β-methylstyrene) in imidazolium- and pyrrolidinium-based ionic liquids, exhibiting a high chemoselectivity towards the epoxide formation, mainly for cyclooctene and (R)-limonene epoxidation, without formation of the corresponding diols. In [BMP][NTf2] (BMP = butyl methyl pyrrolidinium; NTf2 = bis(trifluoromethanesulfonyl)amide), complex 1 exclusively gave trans(R)-limonene 1,2-epoxide, while monometallic catalytic systems led to a low diastereoselectivity. 95Mo NMR studies helped to understand the catalytic behaviour of 1 and 2 in ionic liquid medium.
- Brito, José A.,Ladeira, Sonia,Teuma, Emmanuelle,Royo, Beatriz,Gómez, Montserrat
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experimental part
p. 88 - 95
(2012/02/05)
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- Zirconia-supported Keggin phosphomolybdovanadate nanocomposite: A heterogeneous and reusable catalyst for alkene epoxidation under thermal and ultrasonic irradiation conditions
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Keggin phosphomolybdovanadate, PVMo, was supported on a zirconia matrix by the wet impregnation method. The phase and chemical structure, optical absorption, surface physicochemical properties and morphology of PVMo-ZrO 2 composite were studied by X-ray diffraction (XRD) technique, FT-IR and diffuse reflectance UV-vis spectroscopic (DR UV-vis) methods, and scanning electron microscopy (SEM), which indicated that the primary Keggin structure has remained intact after formation of the composite. Moreover, the obtained nanocomposite was used as an efficient catalyst of olefins under reflux and ultrasonic irradiation conditions. The catalyst was reused several times, without observable loss of activity and selectivity. Indeed, the catalytic activity of the PVMo-ZrO2 was compared with pure Keggin phosphomolybdovanadate.
- Salavati, Hossein,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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experimental part
p. 588 - 596
(2012/05/20)
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- Nanostructured dioxomolybdenum(VI) catalyst for the liquid-phase epoxidation of olefins
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A new organosilica hybrid mesoporous material (HM) containing phosphane oxide surface groups was prepared via the "dual" organosilane templated co-condensation of 4-bis-(triethoxysilyl)benzene and (diphenylphosphanyl)propyltriethoxysilane, followed by post-synthesis oxidation of the phosphane surface groups. The HM material was used to immobilise the [Mo(O)2Cl2] complex. The resultant material (HM-Mo) is an active and selective catalyst in the liquid-phase epoxidation of olefins [cis-cyclooctene, (R)-(+)-limonene, trans-2-octene, 1-octene] with tBuOOH at 55°C and gives comparable epoxide yields to those observed for the free complex [MoCl2(O)2{OP(CH2CH3)(Ph) 2}2] (1), under similar reaction conditions: the crystal structure of complex 1 remains the same after reaction with tBuOOH. The oxidant is essentially consumed in the HM-Mo or 1 catalysed epoxidation of the olefin. In the case of limonene (possesses endo- and exocyclic C=C bonds), the molar ratio of 1,2-epoxy-p-menth-8-ene/1,2-8,9-diepoxy-p-menthane at ca. 90% conversion (reached after 24 h reaction) is ca. 5 and 10 for 1 and HM-Mo, respectively, indicating a favourable regioselectivity towards the epoxidation of the endocyclic C1-C2 double bond, especially in the case of the heterogeneous catalyst.
- Castro, Alichandra,Alonso, Joao C.,Valente, Anabela A.,Neves, Patricia,Brandao, Paula,Felix, Vitor,Ferreira, Paula
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scheme or table
p. 1405 - 1412
(2010/07/16)
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- Dioxomolybdenum(VI) epoxidation catalyst supported on mesoporous silica containing phosphane oxide groups
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A new mesoporous hybrid material (denoted LP-TEPPPOMo) has been prepared by tethering [MoO2Cl2] onto mesoporous silica previously functionalised with phosphane oxide spacer ligands. The LP-TEPPPO-Mo material was tested in the liquid-phase epoxidation of olefins [cis-cyclooctene, (R)(+)-limonene, trans-2-octene and 1-octene] with tBuOOH, at 55 °C, and without a co-solvent, giving at least 90 % selectivity to the corresponding epoxide at 36-77% conversion: in the case of limonene, regioselectivity favours the epoxidation of the endocyclic double bond, giving mainly 1, 2-epoxy-p-menth-8-ene. The catalytic system based on a liquid-liquid biphasic system containing the homogeneous complex [MoCl2(O) 2(OP(CH2CH3)(Ph)2J2] dissolved in the ionic liquid 1butyl-4-methylpyridinium tetrafluoroborate leads to lower epoxide selectivity (91 % at 64 % conversion) in the reaction of cyclooctene in comparison to that observed for LPTEPPPO-Mo (100% at 87% conversion). The reused solidliquid and liquid-liquid biphasic catalytic systems show partial loss of catalytic activity.
- Castro, Alichandra,Alonso, Joao C.,Neves, Patricia,Valente, Anabela A.,Ferreira, Paula
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experimental part
p. 602 - 607
(2010/05/11)
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- Kinetic resolution of trans-cycloalkane-1,2-diols via Steglich esterification
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We describe the efficient and highly enantioselective kinetic resolution of trans-cycloalkane-1,2-diols utilizing an enantioselective Steglich reaction with a variety of carboxylic acids that form the corresponding anhydrides in situ.
- Hrdina, Radim,Mueller, Christian E.,Schreiner, Peter R.
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supporting information; experimental part
p. 2689 - 2690
(2010/07/08)
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- Sonocatalytic oxidation of olefins catalyzed by heteropolyanion-montmorillonite nanocomposite
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A Keggin-type heteropolyanion compound (HPO) was doped within the montmorillonite (MMT) structure by impregnation method. The synthesized catalyst was characterized by FT-IR, XRD, UV-vis, CV, SEM and elemental analysis. Based on chemical adsorption between HPO, and hydroxyl surface groups, HPOs nanoparticles were successfully located on the MMT. Moreover, the obtained nanocomposite was found as an efficient catalyst for oxidation of hydrocarbons under reflux and ultrasonic irradiation conditions.
- Salavati, Hossein,Tangestaninejad, Shahram,Moghadam, Majid,Mirkhani, Valiollah,Mohammadpoor-Baltork, Iraj
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experimental part
p. 145 - 152
(2010/11/18)
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- Iron-catalyzed asymmetric olefin cis-dihydroxylation with 97% enantiomeric excess
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Big cis-ster: The use of an (R,R)-bipyrrolidine backbone with two α-methylpyridine pendant arms affords a tetradentate N4 ligand that coordinates an iron center with cis-α topology (see picture; Fe purple, C gray, N blue, O red, S yellow, F green). This complex catalyzes the reaction between H2O2 and cis-2-heptene to afford a cis-diol product in very high enantioselectivity. (Figure Presented)
- Suzuki, Ken,Oldenburg, Paul D.,Que Jr., Lawrence
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p. 1887 - 1889
(2008/12/22)
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- Enantioselective kinetic resolution of trans-cycloalkane-1,2-diols
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Finally! The title resolution is achieved with a nonnatural, partially rigid, lipophilic tetrapeptide at low catalyst loadings without additional base or cosolvents. The transition-state model (ball-and-stick model in the scheme; C gray, N blue, O red) emphasizes the interplay between hydrogen-bonding and hydrophobic interactions. (Chemical Equation Presented)
- Mueller, Christian E.,Wanka, Lukas,Jewell, Kevin,Schreiner, Peter R.
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supporting information; experimental part
p. 6180 - 6183
(2009/04/06)
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- Iron-catalyzed olefin epoxidation in the presence of acetic acid: Insights into the nature of the metal-based oxidant
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The iron complexes [(BPMEN)Fe(OTf)2] (1) and [(TPA)Fe(OTf) 2] (2) [BPMEN = N,N′-bis-(2-pyridylmethyl)-N,N′-dimethyl- 1,2-ethylenediamine; TPA = tris-(2-pyridylmethyl)amine] catalyze the oxidation of olefins by H2O2 to yield epoxides and cis-diols. The addition of acetic acid inhibits olefin cis-dihydroxylation and enhances epoxidation for both 1 and 2. Reactions carried out at 0°C with 0.5 mol % catalyst and a 1:1.5 olefin/H2O2 ratio in a 1:2 CH 3CN/CH3COOH solvent mixture result in nearly quantitative conversions of cyclooctene to epoxide within 1 min. The nature of the active species formed in the presence of acetic acid has been probed at low temperature. For 2, in the absence of substrate, [(TPA)FeIII(OOH) (CH3COOH)]2+ and [(TPA)FeIVO(NCCH 3)]2+ intermediates can be observed. However, neither is the active epoxidizing species. In fact, [(TPA)FeIVO(NCCH 3)]2+ is shown to form in competition with substrate oxidation. Consequently, it is proposed that epoxidation is mediated by [(TPA)FeV(O)(OOCCH3)]2+, generated from O-O bond heterolysis of the [(TPA)FeIII(OOH)(CH3COOH)] 2+ intermediate, which is promoted by the protonation of the terminal oxygen atom of the hydroperoxide by the coordinated carboxylic acid.
- Mas-Balleste, Ruben,Que Jr., Lawrence
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p. 15964 - 15972
(2008/09/18)
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- Novel transition-metal-free heterogeneous epoxidation catalysts discovered by means of high-throughput experimentation
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Various transition-metal-free oxides have been studied as catalysts for the epoxidation of cyclooctene with hydrogen peroxide by means of high-throughput experimentation. Different boron, aluminium, and gallium oxides were prepared according to various synthesis methods. A number of pure aluminium and gallium oxides showed very good catalytic performances, while the results obtained with boron oxides or mixed oxides were less positive. The best results were obtained with a gallium oxide catalyst, which gave an epoxide yield of 71 % and a selectivity of 99% after reaction for 4 h at 80°C. Gallium oxides had not been reported previously as active epoxidation catalysts. The use of high-throughput experimentation proved useful both for discovering new active catalysts and for identifying a number of relationships between the synthesis conditions and the catalytic properties of the transition-metal-free oxides.
- Pescarmona, Paolo P.,Janssen, Kris P. F.,Jacobs, Pierre A.
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p. 6562 - 6572
(2008/03/15)
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- Ligand topology effects on olefin oxidations by bio-inspired [Fe II(N2Py2)] catalysts
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Linear tetradentate N2Py2 ligands can coordinate to an octahedral FeII center in three possible topologies (cis-α, cis-β, and trans). While for the N,N'-bis(2-pyridylmethyl)-l,2- diaminoethane (bpmen) complex, only the cis-α topology has been observed, for N,N'-bis(2-pyridylmethyl)-1,2-diamino-cyclohexane (bpmcn) both cis-α and cis-β isomers have been reported. To date, no facile interconversion between cis-α and cis-β topologies has been observed for iron(II) complexes even at high temperatures. However, this work provides evidence for facile interconversion in solution of cis-α, cis-β, and trans topologies for [Fe(bpmpn)X2] (bpmpn = N, N'-bis(2-pyridylmethyl)-1,3- diaminopropane; X = triflate, CH3CN) complexes. As reported previously, the catalytic behavior of cis-α and cis-β isomers of [Fe(bpmcn)(OTf)2] with respect to olefin oxidation depends dramatically on the geometry adopted by the iron complex. To establish a general pattern of the catalysis/ topology dependence, this work presents an extended comparison of the catalytic behavior for oxidation of olefins of a family of [Fe(N2py2)] complexes that present different topologies. 18O labeling experiments provide evidence for a complex mechanistic land-scape in which several pathways should be considered. Complexes with a trans topology catalyze only non-water-assisted epoxidation. In contrast, complexes with a cis-α topology, such as [Fe(bpmen)X2] and [Fe(α-bpmcn)-(OTf)2], can catalyze both epoxidation and cis-dihydroxylation through a water-assisted mechanism. Surprisingly, [Fe(bpmpn)X2] and [Fe(β-bpmcn)-(OTf)2] catalyze epoxidation via a water-assisted pathway and cis-dihydroxylation via a non-water-assisted mechanism, a result that requires two independent and distinct oxidants.
- Mas-Balleste, Ruben,Costas, Miquel,Van Den Berg, Tieme,Que Jr., Lawrence
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p. 7489 - 7500
(2007/10/03)
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