4065-81-0Relevant academic research and scientific papers
Incorporation of redox-inactive cations promotes iron catalyzed aerobic C-H oxidation at mild potentials
Chantarojsiri, Teera,Ziller, Joseph W.,Yang, Jenny Y.
, p. 2567 - 2574 (2018)
The synthesis and characterization of the Schiff base complexes Fe(ii) (2M) and Fe(iii)Cl (3M), where M is a K+ or Ba2+ ion incorporated into the ligand, are reported. The Fe(iii/ii) redox potentials are positively shifted by 440 mV
Synthesis, characterization and catalytic activity of a mononuclear nonheme copper(II)-iodosylbenzene adduct
Jeon, Hyeri,Oh, Hana,Hong, Seungwoo
, (2021/07/06)
Iodosylbenzene (PhIO) and its derivatives have attracted significant attention due to their various applications in organic synthesis and biomimetic studies. For example, PhIO has been extensively used for generating high-valent metal-oxo species that have been regarded as key intermediates in diverse oxidative reactions in biological system. However, recent studies have shown that metal-iodosylbenzene adduct, known as a precursor of metal-oxo species, plays an important role in transition metal-catalyzed oxidation reactions. During last few decades, extensive investigations have been conducted on the synthesis and reactivity studies of metal-iodosylbenzene adducts with early and middle transition metals including manganese, iron, cobalt. Nevertheless, metal-iodosylbenzene adducts with late transition metals such as nickel, copper and zinc, still remains elusive. Herein, we report a novel copper(II)-iodosylbenzene adduct bearing a linear ligand composed of two pyridine rings and an ethoxyethanol side-chain, [Cu(OIPh)(HN3O2)]2+ (1). The copper(II)-iodosylbenzene adduct was characterized by several spectroscopic methods including UV–vis spectroscopy, electrospray ionization mass spectrometer (ESI MS), and electron paramagnetic resonance (EPR) combined with theoretical calculations. Interestingly, 1 can carry out the catalytic sulfoxidation reaction. In sulfoxidation reaction with thioanisole under catalytic reaction condition, not only two-electron but also four-electron oxidized products such sulfoxide and sulfone were yielded, respectively. However, 1 was not an efficient oxidant towards C–H bond activation and epoxidation reactions due to the steric hindrance created by the intramolecular H-bonding interaction between HN3O2 ligand and iodosylbenzene moiety.
A Mononuclear Nonheme Iron(IV)-Oxo Complex of a Substituted N4Py Ligand: Effect of Ligand Field on Oxygen Atom Transfer and C-H Bond Cleavage Reactivity
Singh, Reena,Ganguly, Gaurab,Malinkin, Sergey O.,Demeshko, Serhiy,Meyer, Franc,Nordlander, Ebbe,Paine, Tapan Kanti
, p. 1862 - 1876 (2019/01/25)
A mononuclear iron(II) complex [FeII(N4PyMe2)(OTf)](OTf)(1), supported by a new pentadentate ligand, bis(6-methylpyridin-2-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine (N4PyMe2), has been isolated and characterized. Introduction of methyl groups in the 6-position of two pyridine rings makes the N4PyMe2 a weaker field ligand compared to the parent N4Py ligand. Complex 1 is high-spin in the solid state and converts to [FeII(N4PyMe2)(CH3CN)](OTf)2 (1a) in acetonitrile solution. The iron(II) complex in acetonitrile displays temperature-dependent spin-crossover behavior over a wide range of temperature. In its reaction with m-CPBA or oxone in acetonitrile at -10 °C, the iron(II) complex converts to an iron(IV)-oxo species, [FeIV(O)(N4PyMe2)]2+ (2). Complex 2 exhibits the M?ssbauer parameters δ = 0.05 mm/s and ΔEQ = 0.62 mm/s, typical of N-ligated S = 1 iron(IV)-oxo species. The iron(IV)-oxo complex has a half-life of only 14 min at 25 °C and is reactive toward oxygen-atom-transfer and hydrogen-atom-transfer (HAT) reactions. Compared to the parent complex [FeIV(O)(N4Py)]2+, 2 is more reactive in oxidizing thioanisole and oxygenates the C-H bonds of aliphatic substrates including that of cyclohexane. The enhanced reactivity of 2 toward cyclohexane results from the involvement of the S = 2 transition state in the HAT pathway and a lower triplet-quintet splitting compared to [FeIV(O)(N4Py)]2+, as supported by DFT calculations. The second-order rate constants for HAT by 2 is well correlated with the C-H bond dissociation energies of aliphatic substrates. Surprisingly, the slope of this correlation is different from that of [FeIV(O)(N4Py)]2+, and 2 is more reactive only in the case of strong C-H bonds (>86 kcal/mol), but less reactive in the case of weaker C-H bonds. Using oxone as the oxidant, the iron(II) complex displays catalytic oxidations of substrates with low activity but with good selectivity.
Ionic Liquid Stabilized Niobium Oxoclusters Catalyzing Oxidation of Sulfides with Exceptional Activity
Zhou, Qingqing,Ye, Man,Ma, Wenbao,Li, Difan,Ding, Bingjie,Chen, Manyu,Yao, Yefeng,Gong, Xueqing,Hou, Zhenshan
, p. 4206 - 4217 (2019/03/26)
We present here a new class of niobium oxoclusters that are stabilized effectively by carboxylate ionic liquids. These functionalized ILs are designated as [TBA][LA], [TBA][PA], and [TBA][HPA] in this work, in which TBA represents tetrabutylammonium and LA, PA, and HPA refer to lactate, propionate, 3-hydroxypropionate anions, respectively. The as-synthesized Nb oxoclusters have been characterized by use of elemental analysis, NMR, IR, XRD, TGA, HRTEM. It was found that [TBA][LA]-stabilized Nb oxoclusters (Nb?OC@[TBA][LA]) are uniformly dispersed with an average particle size of 2–3 nm and afforded exceptionally high catalytic activity for the selective oxidation of various thioethers. The turnover number with Nb?OC@[TBA][LA] catalyst was over 56 000 at catalyst loading as low as 0.0033 mol % (1 ppm). Meantime, the catalyst also showed the high activity for the epoxidation of olefins and allylic alcohols by using only 0.065 mol % of catalyst (50 ppm). The characterization of 93Nb NMR spectra revealed that the Nb oxoclusters underwent structural transformation in the presence of H2O2 but regenerated to their initial state at the end of the reaction. In particular, the highly dispersed Nb oxoclusters can absorb a large amount of polar organic solvents and thus were swollen greatly, which exhibited “pseudo” liquid phase behavior, and enabled the substrate molecules to be highly accessible to the catalytic center of Nb oxocluster units.
Mn(III)-porphyrin/graphene oxide nanocomposite as an efficient catalyst for the aerobic oxidation of hydrocarbons
Rayati, Saeed,Rezaie, Saghar,Nejabat, Fatemeh
, p. 696 - 703 (2018/04/20)
In this study, manganese porphyrin was grafted on the surface of graphene oxide nanosheets via covalent bonding to produce a heterogeneous catalyst. The prepared nanocomposite was characterized using X-ray diffraction, UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared, and thermogravimetric analysis. Atomic absorption spectroscopy was also used to determine the amount of the loaded catalyst. The catalytic efficiency of the immobilized Mn-porphyrin was investigated for the aerobic oxidation of alkenes and saturated alkanes in acetone under mild reaction conditions. The prepared heterogenized catalyst displays superior catalytic performance as compared to the homogeneous catalyst. Moreover, the excellent turnover number (more than 31,767) achieved for the oxidation of styrene indicates the high longevity of the supported catalyst. The catalyst structure is preserved well after the oxidation reaction and is simply reused at least five times, without any significant loss of the catalytic efficiency.
Synthesis of AgWCNx Nanocomposites for the One-Step Conversion of Cyclohexene to Adipic Acid and Its Mechanistic Studies
Goyal, Reena,Sameer, Siddharth,Sarkar, Bipul,Bag, Arijit,Singhal, Nikita,Bordoloi, Ankur
, p. 16555 - 16565 (2017/11/10)
A novel catalyst composed of silver nanoparticles grafted on WCNx has been prepared by using a facile pH-adjusted method. The material reported in this study presents a non-mineral acid route for the synthesis of the industrially significant monomer adipic acid through the selective oxidation of cyclohexene. Ag has been stabilized in the hydrophobic matrix during the formation of the mesoporous silica material by using aniline as stabilizing agent. A cyclohexene conversion of 92.2 % with 96.2 % selectivity for adipic acid was observed with the AgWCNx-2 catalyst, therefore, the AgWCNx catalyst was found to be efficient for the direct conversion to adipic acid with respect to their monometallic counterparts. The energy profile diagrams for each reaction path by using the AgWCNx catalyst were studied along with their monometallic counterparts by using the Gaussian 09 package. The reported material can avoid the use of harmful phase-transfer catalysts (PTC) and/or chlorinated additives, which are two among other benefits of the reported work.
Rate and Selectivity Control in Thioether and Alkene Oxidation with H2O2 over Phosphonate-Modified Niobium(V)–Silica Catalysts
Thornburg, Nicholas E.,Notestein, Justin M.
, p. 3714 - 3724 (2017/09/12)
Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti?Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb?Zr at all conversions. Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.
Synthesis, crystal structure and characterization a new ionic complex MoO2Cl3(MeOH)·H3tptz·Cl2 (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) as epoxidation catalyst
Maghami, Mahboobeh,Farzaneh, Faezeh,Simpson, Jim,Azarkish, Mohammad
, p. 28 - 36 (2018/03/29)
[MoO2Cl3(MeOH)]·H3tptz·Cl2 (1) (where tptz is 2,4,6-tris(2-pyridyl)-1,3,5-triazine) was prepared via reaction of MoO3 with tptz in a stoichiometric ratio of 1:1 in concentrated HCl at room temperature. It was characterized, by means of elemental analysis, FTIR, UV–Vis, 1H NMR and single-crystal X-ray diffraction. The asymmetric unit of the molybdenum(VI) salt 1 contains a 2,2′,2″-(1,3,5-triazine-2,4,6-triyl)tripyridinium cation, a cis-dioxotrichloridomethanolmolybdenum(VI) monoanion and two chloride anions to achieve electrical neutrality. The oppositely charged components in the structure of 1 are bound together by an intricate system of weak N(O)–H?Cl hydrogen bonds. The interactions between hydrogen bond donor and acceptor giving rise to three dimensional networks. It was also found that compound 1 successfully catalyzes the epoxidation of various alkenes such as cycoloctene, cyclohexene, norbornene, styrene, α-methyl styrene and trans-stilbene with 30–100% conversion and 80–100% selectivity using tert-butyl hydroperoxide (TBHP) as oxidant. The catalyst can be easily recovered from the reaction mixture and reused at least for three times without significant loss of activity. The superior antibacterial activity of 1 against Bacillus subtilis is also described in this presentation.
Highly efficient epoxidation of cyclohexene with aqueous H2O2 over powdered anion-resin supported solid catalysts
Peng,Lu,Ma,Shen,Wei,He,Zhou,Xia
, p. 393 - 399 (2016/08/02)
Resin supported solid acid catalysts have extended the application of conventional solid acid catalysts in the field of selective oxidations. The present work describes selectively catalytic epoxidation of cyclohexene with aqueous 30% H2O2 over powdered anion-resin supported peroxo phosphotungstic acid heterogeneous catalysts prepared through a simple anion-exchange from powdered chloride-form anion resin without any special pre-exchanged treatment. Among these powdered solid catalysts, anion-exchanged resin D201 supported peroxo phosphotungstic acid exhibits the best activity for the titled reaction to obtain 92.4?mol% conversion and 98.1% selectivity of epoxide, for which D201-PWAR(4) behaves as a truly heterogeneous catalyst. Some factors such as various peroxo phosphotungstic acid concentrations, the oxidants, the solvents, the molar ratios of H2O2/cyclohexene, the catalyst amount, the reaction temperature and time play important roles in controlling the epoxidation.
A new Organopalladium compound containing four Iron (III) Porphyrins for the selective oxidation of alkanes/alkenes by t-BuOOH
Singh, Manoj Kumar,Bandyopadhyay, Debkumar
, p. 383 - 389 (2016/03/16)
Two iron(III) tetraphenyl porphyrin catalytic units are connected by an azo-link to form the dimeric compound A. The compound A was then reacted with Pd 2+ to make a tetrameric iron(III) porphyrin complex B with all four iron(III) catalytic sites open to the substrates and reactants. Both the compounds were characterized spectroscopically and the results of homogeneous oxidation of some alkanes and alkenes with t-BuOOH in presence of catalytic quantities of A and B have indicated remarkable improvement in selectivity and efficiency of A over the monomeric catalyst and B over A. [Figure not available: see fulltext.]
