- Towards a zero-waste oxidative coupling of nonactivated aromatics by supported gold nanoparticles
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We show that gold nanoparticles are able to perform the direct oxidative coupling of nonactivated aromatics with O2 as the only co-reagent. In this reaction, the aromatic acts both as reactant and solvent. Biphenyl, for example, can be obtained from benzene with high selectivity and a turnover number (TON) of 230 per pass. Similarly, several substituted biaryls can be prepared. Pd performs only one TON and even when a second catalytic functionality is introduced, together with strong acidic conditions, TON is always lower than 100. Other catalysts require iodine for performing the reaction, leading to 2 kg of waste for 1 kg of biphenyl formed, whereas no waste is created by the oxidative coupling with gold nanoparticles.
- Serna, Pedro,Corma, Avelino
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- Selective Solid State Photooxidant
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Irradiation of biphenyl encapsulated in the cavities of a NaZSM-5 zeolite framework has been reported to result in the formation of an extremely long-lived radical cation. Here, we show that such zeolite encapsulated radical cations can act as irreversible one-electron oxidants for simple alkenes and dienes, in a solid-state analogue to solution-phase cosensitization. Compared to the well-known semiconductor photooxidizers, such as titanium dioxide, the NaZSM-5 zeolite-based solid photooxidants exhibit enhanced selectivity based on oxidation potential, molecular size and shape, and Lewis base character.
- Morkin, Tracy L.,Turro, Nicholas J.,Kleinman, Mark H.,Brindle, Cheyenne S.,Kramer, Wolfgang H.,Gould, Ian R.
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- Organonickel chemistry in the catalytic hydrodechlorination of polychlorobiphenyls (PCBs): Ligand steric effects and molecular structure of reaction intermediates
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Soluble homogeneous organophosphorus - nickel complexes have been used to detoxify polychlorinated biphenyls (PCBs) by catalyzed hydrodechlorination using NaBH2(OCH2CH2OCH3)2 as the hydrogen source. The reactions appear to proceed by NiL3 oxidative addition into C-Cl bonds followed by hydrogenolysis of the metal-carbon bond. In model experiments with decachlorobiphenyl, the cone angle of the organophosphorus ligand L was shown to be a key factor controlling the magnitude and position of chlorine displacement. Hence, ligands leading to para displacement (e.g. (o-MeC6H4O)3P), meta - para displacement (e.g. (EtO)3P and (PhO)3P), and ortho - meta - para displacement (e.g. Me3P and Et3P) were found. Significantly, the highly toxic, coplanar dioxin precursor 3,3′,4,4′-tetrachlorobiphenyl, a meta - para chlorine-substituted congener, was dechlorinated quantitatively with the Et3P catalyst system. Evidence for the presence of organonickel intermediates in the reaction mixtures was obtained by mass spectroscopic and X-ray diffraction studies. Of particular interest is the isolation of square planar complexes p-C6Cl5C6Cl4Ni(PEt3) 2Cl from the reaction of decachlorobiphenyl with NaBH2(OCH2CH2OCH3)2 - (Et3P)2NiCl2 as the catalyst precursor and m-C6Cl5C6Cl4Ni(PEt3) 2Cl from decachlorobiphenyl - Ni(1,5-C8H12)2 - PEt3 at room temperature. All are oxidative addition intermediates and precursors for decachlorobiphenyl hydrodechlorination.
- King, Charles M.,Bruce King,Bhattacharyya, Nripendra K.,Gary Newton
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- Pd nanoparticle supported reduced graphene oxide and its excellent catalytic activity for the Ullmann C-C coupling reaction in a green solvent
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An efficient and easy route to synthesize reduced graphene oxide with well dispersed palladium (Pd) nanoparticles (Pd(0)-RGO) is described. The synthesized materials were fully characterized by different techniques such as: XRD, FTIR, Raman, SEM, and TEM. An average particle size of 7.5 nm for the metal particles was confirmed by TEM analysis. Pd(0)-RGO demonstrated outstanding catalytic activity for Ullmann coupling with 97% yield and good reusability (4 cycles).
- Rana, Surjyakanta,Bidita Varadwaj, G. Bishwa,Jonnalagadda, Sreekantha B.
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- Effect of Cu-Promotion on the Performance of Molybdenum Sulfide for Hydrotreating of FCC Gasoline
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Abstract: Copper sulfide (either supported or unsupported) has received poor attention as promoter since this chalcogenide displayed modest hydrotreatment activity. In this sense, was evaluated the potential of sulfide CuMo catalyst in the FCC gasoline hydrotreatment. A MoS2 bulk and the industrial NiMo/Al2O3 catalyst were used as reference. According to the results obtained, the NiMo commercial catalyst had higher HDS, HDN, and HYD activity, but with a significant decrease in the octane number (RON). While the CuMo catalysts showed a lower response towards hydrotreatment, maintaining its octane value. According to the results obtained in the characterizations carried out (XRD, XPS, TPR, physisorption of N2, among others), we propose that copper species could be generating geometric and/or electronic changes in the CuMoS phases, increasing the number of active sites. Additionally, the incorporation of the Cu in the crystalline structure could be modifying its electronic structure, granting a metallic character to the active phase. The work demonstrates the potential of CuMo catalyst for HDT of FCC gasoline. Graphical Abstract: [Figure not available: see fulltext.].
- Betancourt, Paulino,Pinto-Castilla, Susana
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- Synthesis of NiMo catalysts supported on mesoporous silica FDU-12 with different morphologies and their catalytic performance of DBT HDS
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Mesoporous silica FDU-12 with remarkable morphologies such as hexagonal prisms, spiral rodlike and brick-like, were successfully synthesized under low temperature and strong acidic conditions by introducing of different inorganic salts. The products were characterized by Small-angle X-ray scattering (SAXS) patterns, UV–vis diffuse reflectance Spectroscopy, N2 adsorption-desorption, scanning electron microscopy (SEM), laser Raman spectra (Raman), Fourier transform infrared spectroscopy with pyridine adsorption (pyridine-FTIR), X-ray photoelectron spectrometer (XPS), and transmission electron microscopy (TEM). The results showed that all the samples had high degrees of crystallinity, regular shape, large pore size and specific surface area, while the addition of different inorganic salts had a great influence on the morphology of FDU-12. Furthermore, the DBT HDS performances of FDU-12 supported NiMo hydrodesulfurization (HDS) catalysts were also investigated. The hexagonal prism NiMo/F-HP catalyst had a higher sulfurization degree and more acid sites than other catalysts. The catalytic results indicated that the morphologies and acidities of FDU-12 materials played an essential role in the catalytic performance of DBT HDS over NiMo catalysts. Among the catalysts with different morphologies, the DBT HDS conversions followed the order: hexagonal prism catalyst (NiMo/F-HP)?>?spiral catalyst (NiMo/F-SP)?>?brick-like catalyst (NiMo/F-BL). The highest activity of NiMo/F-HP could be ascribed to the relatively higher acidity, higher sulfurization degree and the better dispersion of the active phases.
- Wang, Xilong,Du, Peng,Chi, Kebin,Duan, Aijun,Xu, Chunming,Zhao, Zhen,Chen, Zhentao,Zhang, Honglei
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- Palladium clusters on dicarboxyl-functional hypercrosslinked porous polymers for oxidative homocoupling of benzene with O2
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Aerobic oxidative homocoupling of benzene with dioxygen (O2) is one of the promising routes for the synthesis of important chemical intermediate biphenyl. In the most cases, high valent palladium (Pd) species are regarded as the active sites, while metallic stage Pd° species are inactive. Herein, we presented the fabrication of highly dispersive Pd clusters with the average size of 1.2 nm on a dicarboxylic acid-functional hypercrosslinked polymer (HCP) with large pore volume and high surface area, which was directly synthesized through the copolymerization of phthalic acid and biphenyl via Bronsted acid-catalyzed Friedel-Crafts alkylation. Catalyst behaved excellent catalytic activity in converting benzene into biphenyl via oxidative homocoupling with O2, exhibiting a high yield up to 18 % plus a record turnover number and turnover frequency as larger as 505 and 253 h?1, respectively. Such catalytic behavior is mainly attributed to the formation of ultrafine Pd clusters promoted by the surface dicarboxyl functional groups.
- Liu, Yangqing,Zou, Chuanbiao,Wang, Kai,Bian, Zhengyun,Jiang, Shi,Zhou, Yu,Wang, Jun
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- Development of reactive Pd/Fe bimetallic nanotubes for dechlorination reactions
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We described the synthesis and characterization of a new class of bimetallic nanotubes based on Pd/Fe and demonstrated their efficacy in the dechlorination of PCB 77, a polychlorinated biphenyl. One-dimensional iron metal nanotubes of different diameters were prepared by electroless deposition within the pores of PVP-coated polycarbonate membranes using a simple technique under ambient conditions. The longitudinal nucleation of the nanotubes along the pore walls was achieved by mounting the PC membrane between two halves of a U-shape reaction tube. The composition, morphology, and structure of the Pd/Fe nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, inductively coupled plasma-atomic emission spectroscopy, and X-ray powder diffraction spectroscopy. The as-prepared Pd/Fe bimetallic nanotubes were used in dechlorination of 3,3′,4,4′-tetrachlorobiphenyl (PCB 77). In comparison with Pd/Fe nanoparticles, the Pd/Fe nanotubes demonstrated higher efficiency and faster dechlorination of the PCB.
- Zahran, Elsayed M.,Bhattacharyya, Dibakar,Bachas, Leonidas G.
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- Zeolite-graphene composite as support for molybdenum-based catalysts and their hydrodesulfurization performance
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A composite of zeolite Y type -graphene as a support doped with molybdenum-cobalt and molybdenum-nickel (active phase and promoter) was synthesized and evaluated as hydrodesulfurization (HDS) catalysts. The ZGMoCo was found to have the ability to reduce the sulfur content by ≈98 % after a 5 h reaction time which is higher compared to the ZMoCo or ZMoNi. This activity can be ascribed to the improved surface area and better distribution of the active phases (molybdenum and cobalt or nickel) on the zeolite Y type -graphene surface. SEM images showed enhanced dispersion of the active phases on the support surface. As per the BET measurements, the surface area was improved due to the introduction of graphene to be 323.6 m2/g ZGMoCo compared to 257.3 m2/g ZMoCo; and 312.5 m2/g for ZGMoNi compared to 245.7 m2/g for ZMoNi. The work offers a convenient approach to prepare an effective HDS catalyst.
- Ali, Islam,Saleh, Tawfik A.
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- The isomers of [12]annulyne and their reactive relationships to heptalene and biphenyl
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(Chemical Equation Presented) [12]Annulyne not like benzyne: The base-initiated condensation of hexadiyne in nonpolar solvents leads directly to the symmetrical isomers of [12]annulyne, i.e. the all cis isomer, which exists as its cumulene, and the 6,9-tr
- Rose, Brad D.,Reiter, Richard C.,Stevenson, Cheryl D.
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- Hydrotalcite-supported palladium nanoparticles as catalysts for the Suzuki reaction of aryl halides in water
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A simple protocol for the Suzuki reaction of aryl halides with phenylboronic acid is proposed. The catalyst used consists of Pd(0) nanoparticles supported on an Mg/Al hydrotalcite. The catalyst was prepared and characterized in this work for the first time. Supported nanoparticles were obtained by depositing a Pd(II) salt onto the support and subsequently reducing it to Pd(0). The greatest novelties of the synthetic process are the use of a hydrogen donor (cyclohexene) to reduce the palladium precursor salt and that of water as solvent in the Suzuki reaction. Biphenyl conversions in the Suzuki reaction of phenylboronic acid with iodobenzene, bromobenzene and chlorobenzene were all excellent, and quantitative yields obtained within a very short time. Even fluorobenzene provided excellent results improving on many reported values for chelated Pd homogeneous catalysts. No homocoupling reaction was detected; also, although homogeneous and heterogeneous catalysis coexist, the catalyst can be recovered for reuse with no loss of activity.
- Burrueco,Mora,Jiménez-Sanchidrián,Ruiz
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- Photon- and electron-induced chemistry of chlorobenzene on Ag(111)
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The surface chemistry, induced by UV photons and low energy electrons, of chlorobenzene (C6H5Cl) on Ag(111) has been studied.C6H5Cl adsorbs molecularly on Ag(111) at 100 K and desorbs molecularly at 170 K (physisorbed) and 230-240 K (chemisorbed) with no thermal decomposition.The adsorption is accompanied by a surface work function change (ΔΦ) of -0.65 eV at one monolayer and -0.9 eV at multilayer coverages.Both UV photons and low energy electrons induce the decomposition of adsorbed C6H5Cl.The energy threshold for the decomposition is 3.5-3.8 eV for photons and ca. 5 eV for electrons.For photons and 21 cm2 at 254 nm and decreases with increasing wavelength.The cross section for the electron-induced decomposition (EID) is 8 x 1017 cm2 (upper limit) at 50 eV and decreases with electron energy.The photodissociation on the surface is ascribed to direct photon induced n -> ?* transition and/or photoexcited electron attachment processes.Compared to the gas phase, the photodissociation threshold is red shifted.This is qualitatively explained by direct excitation process assuming an effective stabilization of the excited C6H5Cl by Ag(111) (strong adsorbate-substrate interactions) and/or "hot" electrons.EID by 12 eV electrons also involves ionization processes.
- Zhou, X.-L.,White, J. M.
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- Complete and truly catalytic degradation method of PCBs using Pd/C-Et3N system under ambient pressure and temperature
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Since PCBs are persistent toxic pollutants and do not degrade easily, the development of a safe and perfect methodology for destruction of such remains is of great importance. We have found that the catalyst activity of Pd/C toward the hydrodechlorination of PCBs was outstandingly activated by the addition of triethylamine. PCBs could be thoroughly dechlorinated under ambient temperature and pressure, and no product other than biphenyl has been detected by GC/MS.
- Sajiki, Hironao,Kume, Akira,Hattori, Kazuyuki,Nagase, Hisamistu,Hirota, Kosaku
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- Catalytic hydrogenolysis of an aryl-aryl carbon-carbon bond with a rhodium complex
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In catalytic hydrogenolysis of an aryl-aryl carbon-carbon bond with a rhodium complex, we used a rhodium system that should provide a thermodynamically favored C-C cleavage complex by making strong metal-aryl bonds. The cleavage of the well-hidden carbon-carbon bond of biphenylene is described which relies both on a strained four membered ring and on the formation of a stable pentametallacycle. The results show that C-H activation and coordination are probably involved in the process leading to C-C bond cleavage.
- Perthuisot,Jones
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- Practical and scalable synthesis of bench-stable organofluorosilicate salts
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Silanes have enjoyed significant success as synthetic tools in the last few decades. In many of the reactions that use silanes, a pentacoordinate silicate is proposed as the reactive intermediate. Despite this, there is no general method to synthesize pentacoordinate fluorosilicates and use them as reagents instead of organo- or alkoxysilanes. Herein, we report the first practical synthesis of organotetrafluorosilicates. The method is tolerant of a number of different functional groups including electrophiles with preferential attack of the fluoride on the silane rather than the electrophile. This transformaton is generally high yielding, even at the mole scale. Furthermore, we demonstrate that organotetrafluorosilicates are both more reactive than the corresponding trialkoxysilanes and more stable under solvolytic conditions. Organotetrafluorosilicates can be used as substrates for a variety of coupling reactions, oxidations, and radical reactions. Overall, organotetrafluorosilicates represent a new platform on which to develop challenging transformations.
- Posz, Jarett M.,Harruff, Stephan R.,Van Hoveln, Ryan
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- Desulfurization of dibenzothiophene and oxidized dibenzothiophene ring systems
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Lithium, used in conjunction with sodium metal, produces a high yield of biphenyl when reacted with dibenzothiophene, dibenzothiophene sulfoxide or dibenzothiophene sulfone.
- Morales, Diego P.,Taylor, Alexander S.,Farmer, Steven C.
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- Promotional effects of magnesia on catalytic performance of Pt/SiO2 in hydrogenolysis of dibenzofuran
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Developing mechanistic insights into the promotional effect of alkaline earth metal oxides in the hydrogenolysis of lignin-derived dibenzofuran (DBF) is key to rational design of high-performance catalysts for bio-oils upgrading. The promotional effect of MgO on Pt/SiO2 catalyst for the hydrogenolysis of DBF has been investigated. Small amounts of MgO enriches the electron density of Pt surface and the Lewis acidity of support, leading to significant improvement of the reactivity with an excellent turnover frequency (TOF) of 1182 h?1 on Pt/3MgO/SiO2 compared with 789 h?1 on Pt/SiO2. The high selectivity for biphenyl depends on the combination of the acid-base properties. With the same moles of alkaline earth dopants, the activity of dopants decreased in the order: Mg > Ca > Sr > Ba, resulting from the decrease in Pt dispersion, and, decreasing linearly with decreasing electronegativity. Additionally, in 240 h stability test, Pt/3MgO/SiO2 catalyst showed considerably stable activity and selectivity.
- Zhang, Jie,Li, Chuang,Chen, Xiao,Chen, Yujing,Zhang, Liyun,Zhang, Bingsen,Liang, Changhai
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- AMINE ASSISTED PHOTODECHLORINATION OF 4-CHLOROBIPHENYL. A COMMENT ON THE MECHANISM
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The Stern-Volmer plot of the aliphatic amine assisted photodechlorination of 4-chlorobiphenyl was analyzed on the basis of the generalized Stern-Volmer expression for bimolecular photochemical reactions which can occur from both the excited singlet and triplet states of a reactant.This kinetic treatment showed that the reaction from the singlet state is more efficient than that from the triplet.
- Ohashi, Mamoru,Tsujimoto, Kazuo
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- Synthesis, characterization and catalytic performance of meso-microporous material Beta-SBA-15-supported NiMo catalysts for hydrodesulfurization of dibenzothiophene
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Micro-mesoporous composite material Beta-SBA-15 (BS) with the Beta structure and SBA-15 mesoporous structure was synthesized and used as catalyst support for hydrodesulfurization (HDS) of dibenzothiophene (DBT). The supports and catalysts were characterized by various techniques including XRD, nitrogen adsorption, SEM, TEM, 27Al MAS NMR, and Pyridine-FTIR. The characterization results demonstrated that NiMo/BS had similar acidity to NiMo/Beta, and possessed more acid sites and stronger acidity than NiMo/SBA-15 and NiMo/Al2O3. Activity evaluation results showed that NiMo/BS exhibited the highest DBT HDS activity among all the catalysts that were studied, and the DBT conversion on NiMo/BS was about 1.6 times as much as that on NiMo/Al2O3 at weight time of 0.75 g min mol -1. The better catalytic performance of NiMo/BS was attributed to the superiorities of the pore structure and large amounts of acid sites of micro-mesoporous BS.
- Zhang, Dengqian,Duan, Aijun,Zhao, Zhen,Wang, Xianqin,Jiang, Guiyuan,Liu, Jian,Wang, Chengyin,Jin, Mingcheng
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- Efficient catalysis of the Suzuki-Miyaura reaction under mild conditions with cyclopalladated N,N-dimethylaminomethylferrocene
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High catalytic activity of N,N-dimethylaminomethylferrocene cyclopalladated derivative was demonstrated in the the Suzuki-Miyaura cross-coupling of aryl bromides with phenylboronic acid, which allowed us to carry out the reaction under extremely mild conditions.
- Gorunova,Zykov,Livantsov,Kochetkov,Grishin,Dunina
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- A residue-free production of biaryls using supported gold nanoparticles
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Small gold nanoparticles in the presence of O2 are able to cleave CH bonds of non-activated arenes and facilitate catalytic formation of biaryls under mild conditions. This procedure avoids the common requirement of iodine, acids, bases, and/or other stoichiometrical additives to accomplish multiple turnovers and results in a zero-waste synthetic process. A number of unactivated arenes such as benzene, toluene, p-xylene, nitrobenzene, chlorobenzene, or phenol are selectively converted to the corresponding biaryls, with accumulated turnover numbers greater than 600. Kinetic measurements, in combination with IR, HRTEM, and STEM-HAADF data, suggest that the reaction takes place on gold atoms that are metallic in character, with the highest CC bond formation rate provided by gold nanoparticles of approximately 3 nm of diameter. A radical-free reaction mechanism is postulated on the basis of the kinetic measurements. The results represent a first stone for the waste-free preparation of biaryls using supported gold catalysts.
- Serna, Pedro,Corma, Avelino
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- Highly active palladium-based catalyst system for the aerobic oxidative direct coupling of benzene to biphenyl
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A highly efficient Pd-containing catalytic system for the intermolecular direct C-H homocoupling of benzene to biphenyl has been developed. The catalytic system was composed of Pd(OAc)2 with trifluoromethanesulfonic acid (TfOH) as an additive and O2 as the sole oxygen source in the absence of any metal-containing cocatalyst. An excellent efficiency of PdII with the acidic additive was attained in the aerobic oxidation of benzene to biphenyl. A high yield (25.3 %) and selectivity (98 %) were achieved by using a small amount of Pd(OAc)2 (0.07 mol %) and TfOH, which gave a high turnover number (180) for Pd species. Theoretical calculation by DFT and UV/Vis absorption spectra illustrated that the formation of electropositive PdII species in the presence of TfOH contributed to the high efficiency of the catalytic system. The acids have it: A highly efficient Pd-based catalytic system is constructed for the direct oxidative coupling of benzene with dioxygen to biphenyl with the C-H activation strategy. The system exhibits an extremely high turnover number of 180, which is accomplished with the aid of CF3SO3H without a metal-bearing cocatalyst.
- Liu, Yangqing,Wang, Xiaochen,Cai, Xiaochun,Chen, Guojian,Li, Jing,Zhou, Yu,Wang, Jun
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- Dechlorination of 4-chlorobiphenyl using NaBH4 at 120-310°C in high boiling inert solvents with and without LiCl
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Dechlorination of 4-chlorobiphenyl with NaBH4 in high boiling inert solvents from 120-310°C were studied. Complete dechlorination occurred in NaBH4/tetraglyme at 310°C in one hour. Adding LiCl to NaBH4 promoted dechlorination in di-, tri, and tetraglyme respectively at 120-135°C. The rate was significantly enhanced when NaBH4, LiCl, and glyme were prestirred at room temperature for 20 minutes before heating to 120-135°C. At equivalent conditions, dechlorination rates followed the order: tetraglyme > triglyme > diglyme. 4-Chlorobiphenyl dechlorination failed using NaBH4/diphenyl ether. In pentamethyldiethylenetriamine 3- and 4-N,N-dimethylaminobiphenyl was produced through a benzyne intermediate.
- Yang, Cangming,Pittman Jr., Charles U.
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- Sc3+-triggered oxoiron(IV) formation from O2 and its non-heme iron(II) precursor via a Sc3+-peroxo-Fe3+ intermediate
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We report that redox-inactive Sc3+ can trigger O2 activation by the FeII(TMC) center (TMC = tetramethylcyclam) to generate the corresponding oxoiron(IV) complex in the presence of BPh 4- as an electron donor. To model a possible intermediate in the above reaction, we generated an unprecedented Sc3+ adduct of [FeIII(η2-O2)(TMC)]+ by an alternative route, which was found to have an Fe3+-(μ- η2:η2-peroxo)-Sc3+ core and to convert to the oxoiron(IV) complex. These results have important implications for the role a Lewis acid can play in facilitating O-O bond cleavage during the course of O2 activation at non-heme iron centers.
- Li, Feifei,Van Heuvelen, Katherine M.,Meier, Katlyn K.,Muenck, Eckard,Que, Lawrence
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- Photochemistry of dibenzothiophene-S,S-dioxide: Reactions of a highly constrained biradical
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Photolysis of dibenzothiophene sulfoxide in isopropranol provides biphenyl in quantitative yield via two sequential photochemical reactions. Mechanistic aspects of the reaction are discussed, including the unusual observation that isoprene increases the quantum of loss of starting material.
- Jenks, William S.
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- Partitioning, desorption, and dechlorination of a PCB congener in sediment slurry supernatants
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Partitioning and desorption played specific roles in the dechlorination of 2-chlorobiphenyl (2-CIBP) in sediment slurry supernatants, which are suspensions of dissolved organic matter (DOM). In short-term experiments, the partition coefficient (Kp) was related to the apparent dechlorination rate constant. The Kp value (160 L gDOC_1), which is independent of the DOM concentration, was determined based on the decrease of the apparent rate constant with the increase of the DOM concentration. In the long-term experiments, the overall rate of dechlorination can be described with a two-compartment model. The time constant for the sediment compartment was related to Kp and the desorption rate constant (kd). The kd value (0.21 h-1) was determined based on the decrease of the time constant values with an increasing DOM concentration. The use of DOM suspensions allowed a short time for equilibrium. Separation of the aqueous and DOM phases was not needed due to the dechlorination of 2-CIBP. The fundamental relationships between overall dechlorination rate constant and properties of the contaminant and sediment were established.
- Fang, Yuanxiang,Al-Abed, Souhail R.
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- Kinetic Control in Two-Electron Homogeneous Redox Electrocatalysis. Reduction of Monohalobiphenyls
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Kinetic control of the two-electron electrocatalytic dehalogenation of monohalobiphenyls to biphenyl was elucidated by analyzing voltammetric data with expanded-grid digital simulation/nonlinear regression.The method involves comparing goodness of fit of limited and mixed kinetic simulation models to the data and is applicable to second-order conditions.The rate-determining step in the dehalogenations was confirmed as electron transfer between the electrochemically generated phenanthridine anion radical and 4-chloro- (4-CB) and 4-bromobiphenyl (4-BB), rather than decomposition of the halobiphenyl anion radical.Rate constants for this step of (1.42 +/- 0.12) * 103 M-1 s-1 for 4-CB and (5.1 +/- 1.8) * 104 M-1 s-1 for 4-BB showed considerably improved precision (and accuracy in the latter case) over rate constants obtained under pseudo-first-order conditions, where the catalytic current had to be extracted from large currents for direct reduction of excess substrate.The simulation/regression method is general for two-electron homogeneous electrocatalytic reactions following similar mechanisms.Synthetic data were used to show that, for systems under mixed kinetic control, rate constants for both homogeneous electron transfer and decomposition of the haloaromatic anion radical can be estimated simultaneously.
- Arena, James V.,Rusling, James F.
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- PHENYL-PHENYL COUPLING IN TRIPHENYLANTIMONY CATALYSED BY PALLADIUM(0)
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The Pd(0) induced coupling of phenyl groups in triphenylantimony to afford diphenyl and Sb(0) has been studied in a search for possible intermediates. Two complexes containing antimony and palladium have been isolated.Their structures have been determined by x-ray crystallography.Complex 1 is made up of triphenylantimony coordinated to palladium diacetate.It affords diphenyl nearly quantitatively on pyrolysis.Complex 2 contains a phenyl-palladium ?-bond as well as two coordinated triphenylantimony residues.
- Barton, Derek H. R.,Khamsi, Jamal,Ozbalik, Nubar,Reibenspies, Joe
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- Magnetically retrievable silica-based nickel nanocatalyst for Suzuki-Miyaura cross-coupling reaction
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A new magnetically recoverable silica-based nickel nanocatalyst was synthesized, characterized and applied for the first time as a catalyst in Suzuki-Miyaura cross-coupling reaction. Excellent catalytic activity, ease of recovery and reusability up to six cycles without appreciable loss of performance make the present protocol beneficial from industrial and environmental viewpoints.
- Sharma, Rakesh Kumar,Yadav, Manavi,Gaur, Rashmi,Monga, Yukti,Adholeya, Alok
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- Addition of manganese to alumina and its influence on the formation of supported NiMo catalysts for dibenzothiophene hydrodesulfurization application
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The influence of adding manganese to NiMo/Al2O3 hydrodesulfurization (HDS) catalysts was studied by impregnation of manganese acetate at the surface of an Al2O3 support obtained by a sol–gel method. The as-obtained Mn-containing alumina supports were then impregnated with nickel nitrate, Ni(NO3)2·6H2O, and ammonium heptamolybdate, (NH4)6Mo7O24·4H2O, dried at 120?°C for 12?h, and finally calcined in air at 400?°C for 4?h. The different solids were then sulfided using 10?mol.% H2S in H2 at 400?°C for 4?h and evaluated in the hydrodesulfurization of dibenzothiophene (DBT) at T?=?300?°C and P?=?30 bars H2. Catalysts were characterized at each step of the preparation: after drying, after calcination, and finally in the sulfided state. Both the pH of the impregnation solution of Ni and Mo precursors and the Mn content (1 or 5?mol.% as MnO) strongly influence the nature of the Ni and Mo species formed. In this respect, the pH of the impregnation solution plays a critical role at low Mn content (1?mol.%). While impregnation at pH 7 results in well-dispersed molybdate species easily sulfided into a highly Ni-promoted MoS2 phase, increasing the pH to 9 favors the formation of more polymerized Mo species and the loss of some nickel into a NiMnO spinel, leading after sulfidation to a lower promotion degree and a lower dispersion. At higher Mn content (5?mol.%), whatever the pH of impregnation, the formation of MoO3 clusters and the loss of Ni into a NiMnO spinel phase leads to deleted HDS activity after sulfidation. Finally, our results also demonstrate a strong positive influence of manganese on the intrinsic activity of the NiMoS phase if conditions of preparation are optimized.
- López-Benítez,Berhault,Guevara-Lara
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- Hydrodesulfurization of dibenzothiophene using Pd-promoted Co-Mo/Al2O3 and Ni-Mo/Al2O3 catalysts coupled with ionic liquids at ambient operating conditions
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Sulfur compounds in fuel oils are a major source of atmospheric pollution. This study is focused on the hydrodesulfurization (HDS) of dibenzothiophene (DBT) via the coupled application of 0.5 wt% Pd-loaded Co-Mo/Al2O3 and Ni-Mo/Al2O3 catalysts with ionic liquids (ILs) at ambient temperature (120 °C) and pressure (1 MPa H2). The enhanced HDS activity of the solid catalysts coupled with [BMIM]BF4, [(CH3)4N]Cl, [EMIM]AlCl4, and [(n-C8H17)(C4H9)3P]Br was credited to the synergism between hydrogenation by the former and extractive desulfurization and better H2 transport by the latter, which was confirmed by DFT simulation. The Pd-loaded catalysts ranked highest by activity i.e. Pd-Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Ni-Mo/Al2O3 > Co-Mo/Al2O3. With mild experimental conditions of 1 MPa H2 pressure and 120 °C temperature and an oil:IL ratio of 10:3.3, DBT conversion was enhanced from 21% (by blank Ni-Mo/Al2O3) to 70% by Pd-Ni-Mo/Al2O3 coupled with [(n-C8H17)(C4H9)3P]Br. The interaction of polarizable delocalized bonds (in DBT) and van der Waals forces influenced the higher solubility in ILs and hence led to higher DBT conversion. The IL was recycled four times with minimal loss of activity. Fresh and spent catalysts were characterized by FESEM, ICP-MS, EDX, XRD, XPS and BET surface area techniques. GC-MS analysis revealed biphenyl as the major HDS product. This study presents a considerable advance to the classical HDS processes in terms of mild operating conditions, cost-effectiveness, and simplified mechanization, and hence can be envisaged as an alternative approach for fuel oil processing.
- Muhammad, Yaseen,Rahman, Ata Ur,Rashid, Haroon Ur,Sahibzada, Maria,Subhan, Sidra,Tong, Zhangfa
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Read Online
- Silver(I) and copper(II)-imidazolium carboxylates: Efficient catalysts in Ullmann coupling reactions
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The silver(I) and copper(II)-imidazolium carboxylate coordination assemblies were derived from the reaction between corresponding carboxylic acid ligands and metal salts. These new metal derivatives depict a novel structural motif with variable chemical and thermal properties. These metal complexes act as potential catalysts in Ullmann coupling reactions. The imidazolium linker present in these complexes plays a role as both ligand and counter ion to balance the metal charge.[Figure not available: see fulltext.].
- Prabusankar, Ganesan,Babu, Chatla Naga,Rajua, Gembali,Sampath, Natarajan
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Read Online
- A mild and efficient process for detoxifying polychlorinated biphenyls
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Polychlorinated biphenyls (PCBs) were effectively dechlorinated to biphenyl under mild conditions using an aqueous solution of sodium hypophosphite in the presence of a palladium catalyst.
- Boyer,McKenna,Karliner,Nirsberger
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Read Online
- Photoelectrocatalytic reduction of 4-Chlorobiphenyl Using Anion radicals and Visible Light
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Excitation of electrochemically generated anion readicals of anthracene and 9,10-diphenylanthracene with visible light (>740 nm) gave greater than 10-fold increases in the rates of reductive dechlorination of 4-chlorobiphenyl.Peak shapes and potentials of cyclic voltammograms of the hydrocarbon catalysts alone with the light on indicated an increase in the rate of mass transport to the glassy carbon electrode caused by convective thermal gradients.However, less than 4percent of the light-assisted increase in electrocatalytic rate constant could be explained by a localized increase in temperature of the reaction layer near the electrode.Good agreement of current-potential data from illuminated electrodes with a model for a two-electron electrocatalytic dark reaction allowed computation of a conditional rate constant by nonlinear regression analysis of the voltammetric data, even in the presence of an exponantially increasing background current.Kinetic results suggested the establishment of a fast, light-assisted reduction pathway, featuring either a photoexcited anion radical of the catalyst or an electron ejected from the excited anion radical as a powerful reducing agent.
- Shukla, Shyam S.,Rusling, James F.
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Read Online
- Palladium-catalyzed aryl group transfer from triarylphosphines to arylboronic acids
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A study of Pd-catalyzed arylation of arylboronic acids with triarylphosphines is presented. Various parameters of this transformation, such as the oxygen presence, choice of solvent, temperature, palladium source, bases and oxidants, were tested and the optimal conditions of the aryl transfer were determined. The effect of electron-withdrawing and electron-donating substituents on the aryl groups of both reactants was also investigated. The unusual transfer of the acetate group from Pd(OAc)2 to p-nitrophenylboronic acid in the presence of PAr3 is reported. A plausible mechanism of the Pd-catalyzed aryl group transfer from PAr3 to the arylboronic acid is proposed.
- Enright, Dale R.,Gogate, Akash R.,Smoliakova, Irina P.,Vasireddy, Purna C. R.
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- A Photoreactive Iron(II) Complex Luminophore
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Controlling the order and lifetimes of electronically excited states is essential to effective light-to-potential energy conversion by molecular chromophores. This work reports a luminescent and photoreactive iron(II) complex, the first performant group homologue of prototypical sensitizers of ruthenium. Double cyclometalation of a phenylphenanthroline framework at iron(II) favors the population of a triplet metal-to-ligand charge transfer (3MLCT) state as the lowest energy excited state. Near-infrared (NIR) luminescence exhibits a monoexponential decay with τ = 2.4 ns in the solid state and 1 ns in liquid phase. Lifetimes of 14 ns at 77 K are in line with a narrowing of the NIR emission band at λem,max = 1170-1230 nm. Featuring a 3MLCT excited-state redox potential of -2 V vs the ferrocene/ferrocenium couple, the use of the Fe(II) chromophore as a sensitizer for light-driven synthesis is exemplified by the radical cross-coupling of 4-chlorobromobenzene and benzene.
- Argüello Cordero, Miguel A.,Berkefeld, Andreas,Leis, Wolfgang,Lochbrunner, Stefan,Schubert, Hartmut
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supporting information
p. 1169 - 1173
(2022/02/05)
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- Research on the decomposition kinetics and thermal hazards of aniline diazonium salt
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Diazotization reaction, strong exothermic characteristics and thermal instability of diazonium salts make the production process high risk. To research thermal hazards of aniline diazonium salt, dynamic experiments are carried out by the differential scanning calorimeter (DSC) to obtain thermodynamic parameters. Moreover, the kinetic parameters are analyzed by Advanced Kinetics and Technology Solutions (AKTS) software. Finally, the GC-MS and UV spectrum are used to further study the decomposition mechanism of the aniline diazonium salt. The results indicate that aniline diazonium salt is very easy to decompose. When the heating rate is 2 K/min, the onset decomposition temperature is only 27.21 ℃ (Tonset). The apparent activation energy of the decomposition process calculated by Friedman and Ozawa methods are respectively 98-85 kJ/mol and 110-100 kJ/mol. Under the ideal adiabatic conditions (φ = 1), the initial temperatures of TMRad for 24 h is only 6.2 ℃ (TD24), which is predicted by the AKTS software. The decomposition process of aniline diazonium salt is inconsistent with a single reaction mechanism.
- Du, Lei,Wang, Ben,Xie, Chuanxin,Yuan, Yucan
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- Silk?Fibroin-Supported Palladium Catalyst for Suzuki-Miyaura and Ullmann Coupling Reactions of Aryl Chlorides
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Recently, we have reported the preparation of a silk fibroin-supported Palladium catalyst (Pd/SF) and its use in the Suzuki-Miyaura cross-coupling of aryl iodides. Since its synthetic applicability and structural features are still far from being fully ex
- Albano, Gianluigi,Farinola, Gianluca M.,Giannini, Cinzia,Musio, Roberta,Omenetto, Fiorenzo G.,Rizzo, Giorgio,Sibillano, Teresa
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supporting information
(2022/02/03)
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- AgF-Mediated Electrophilic Amination of Alkoxyarylsilanes with Azodicarboxylates
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A facile and efficient AgF-mediated electrophilic amination of alkoxyarylsilanes with azodicarboxylates was developed. The reaction proceeds in green solvent under simple and mild conditions to generate the corresponding aryl hydrazines. AgF acts both as a stoichiometric fluoride source and a reagent for transmetalation to the arylsilver intermediate that eventually reacts with azodicarboxylates to provide aryl hydrazines.
- Deng, Shijun,Li, Dong,Shimokawa, Jun,Yorimitsu, Hideki,Zhang, Qian
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supporting information
(2022/01/31)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Pyrazole-Mediated C-H Functionalization of Arene and Heteroarenes for Aryl-(Hetero)aryl Cross-Coupling Reactions
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Herein we introduce a transition-metal-free protocol that involves a commercially available, inexpensive pyrazole molecule to conduct C-C cross-coupling reactions at room temperature via a radical pathway. Using this method, an aryldiazonium salt has been coupled to a wide range of arenes and heteroarenes including benzene, mesitylene, thiophene, furan, benzoxazole to result the corresponding biaryl products. The full reaction mechanism is elucidated along with the crystallographic probation of an active initiator species. A potassium-stabilized deprotonated pyrazole steers single-electron transfer to the substrate and behaves as an initiator for the reaction.
- Kundu, Abhishek,Dey, Dhananjay,Pal, Subhankar,Adhikari, Debashis
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p. 15665 - 15673
(2021/11/16)
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- Catalyst-free synthesis of phenanthridinesviaelectrochemical coupling of 2-isocyanobiphenyls and amines
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Catalyst free synthesis of 6-aryl phenanthridines and amides through an electrochemical reaction is reported in this study. The coupling reaction proceeds by the cathodic reduction ofin situformed diazonium ions, which are formed from anilines and an alkyl nitrite. The generated aryl radical diazonium ions coupled from isocyanides furnished the desired products in good yields. This cascade reaction was conducted in an undivided cell equipped with an RVC as the anode and Pt as the cathode usingnBu4NBF4as the electrolyte at room temperature. A series of detailed mechanistic studies have also been performed, including a radical clock experiment and cyclic voltammetry analysis.
- Malviya, Bhanwar Kumar,Singh, Karandeep,Jaiswal, Pradeep K.,Karnatak, Manvika,Verma, Ved Prakash,Badsara, Satpal Singh,Sharma, Siddharth
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p. 6367 - 6378
(2021/04/16)
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- Bulk hydrotreating MonW12-nS2 catalysts based on SiMonW12-n heteropolyacids prepared by alumina elimination method
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A series of unsupported mono- and bimetallic MonW12-nS2 catalysts were synthesized by alumina elimination from supported MonW12-nS2/Al2O3 samples using acid etching. Alumina supported catalysts have been in turn prepared by using monometallic H4SiMo12O40 and H4SiW12O40 heteropolyacids (HPAs), their mixture with Mo/W atomic ratio equal to 1/11 and 3/9, and mixed bimetallic H4SiMo1W11O40 and H4SiMo3W9O40 HPAs. All catalysts were characterized by N2 adsorption, temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), extended X-ray absorption fine structure (EXAFS) spectroscopy and powder X-ray diffraction (XRD) and their performance were evaluated in simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of naphthalene. The etching process led to a successful removal of all the support and of the partially sulfided species, with sulfidation degrees of both Mo and W above 90 % on the final bulk solids. The active phase also underwent a rearrangement, as higher average length and stacking were measured on the bulk catalysts than on the original supported ones. Mixed MoWS2 phase was evidenced in all solids, prepared from mixed HPAs (MonW12-nS2) or from the mixture of monometallic HPAs (RefMonW12-nS2), by EXAFS and ToF-SIMS, with however a larger quantity on the MoW solids. It seems that the mixed MoWS2 phase observed on the supported MoW catalysts is maintained through the etching process, while on RefMonW12-nS2 the mixed phase, observed in a much lesser extent in the corresponding supported catalyst, could result from the aggregation of the monometallic slabs. MonW12-nS2 catalysts were found more effective than the monometallic catalysts and than the corresponding RefMonW12-nS2, in both dibenzothiophene hydrodesulfurization and naphthalene hydrogenation, which was related to the presence of the mixed phase maintained through the etching of the support.
- Kokliukhin,Nikulshina,Mozhaev,Lancelot,Lamonier,Nuns,Blanchard,Bugaev,Nikulshin
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- The use of inorganic Al-HMS as a support for NiMoW sulfide HDS catalysts
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Inorganic hexagonal mesoporous silica (HMS) and aluminum modified HMS materials (Al-HMS) were prepared and used as supports of transition metal sulfide hydrodesulfurization (HDS) catalysts based on nickel, molybdenum, and tungsten as active phase. The samples were characterized with XRD, HRTEM, TPD, N2 physisorption and UV–Vis. The catalytic activity of the trimetallic catalysts was performed in the HDS of dibenzothiophene (DBT). When Al was incorporated into the inorganic support, important changes and effects were observed on the physicochemical properties. On the other hand, the incorporation of Al into the HMS led to a decrease in the reaction rate (k) and a trend toward a direct path of desulfurization was observed for all materials.
- Alonso-Nú?ez, G.,Huirache-Acu?a, R.,Maya-Yescas, R.,Pawelec, B.,Rivera-Mu?oz, E. M.,Vázquez, P. J.,Zepeda, T. A.
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- Effect of pre-activation treatment temperature on hydrodesulfurization catalytic activity of CoMoS/KIT-6
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Mesoporous silica-supported cobalt–molybdenum hydrodesulfurization catalysts have been prepared by wetness impregnation, drying and a thermal pre-treatment of impregnated support before activation. Characterization of materials was made by nitrogen adsorption, thermogravimetric analysis, Raman spectroscopy, TEM and XPS. Catalytic activity was determined by hydrodesulfurization of dibenzothiophene (DBT). The results indicate that the thermal pre-treatment carried out at the lower temperature allows the formation of smaller and less stacked active phase structures, with a higher amount of CoMoS phase.
- Beltrán, Karen A.,Alvarez-Contreras, Lorena,Delgado, Anabel D.,Leyva-Porras, César C.,Aguilar-Elguezabal, Alfredo
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p. 106 - 115
(2019/11/26)
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- Novel Molybdenite-Based Nanopowder Catalysts for Hydrodesulfurization
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Abstract: Novel bulk single-component sulfide catalysts were prepared under theconditions of solid-phase dispersion of МoS2 molybdeniteat various mechanical treatment times and various amounts of polar and nonpolarliquid microadditives. The chemical degradation of the samples in the air wasfound to lead to the formation of surface sulfate anions that shieldcatalytically active Mo sites. Indirect correlations of the hydrodesulfurizationability of MoS2 powders with the concentration of sulfateanions on their surface, and with the aqueous pH in the powder suspensions,including the dielectric permittivity of the organic dopants, can serve asreference indicators of high catalytic activity in the model reaction ofdibenzothiophene hydrogenolysis. The study identified the most active sampleable to run for an extended time during multiple cycles without losing itscatalytic properties. Also, the paper discusses the dibenzothiophene conversionroutes, the product composition, the probable structure of active sites in thecatalysts, and the desulfurization degree of diesel fuel components. [Figure not available: see fulltext.]
- Fedushchak,Uimin,Maikov,Akimov,Zhuravkov,Vosmerikov,Prosvirin,Velichkina,Stepanov,Kogan
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p. 794 - 805
(2021/07/14)
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- Synergy effect of boron and cobalt in B2O3-SBA-15-(Co)Mo catalyst for efficient hydrodesulfurization of liquid fuels
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The contributory effect of surface acidity is significant to desulfurize heavy recalcitrant organosulfur compounds effectively. This research explores the synergistic effect of boron and cobalt in CoMoS supported on B2O3-SBA-15 for ultradeep hydrodesulfurization (HDS) of DBT and MDBT in the model and diesel fuel, respectively. The catalysts prepared consisting of SBA-15-(Co)Mo, representing (SM and SMC) and B2O3-SBA-15-(Co)Mo for BSM and BSMC, were fully characterized to gain insight into the structural activity concerning the nature of the fuel and the organosulfur compound employed. The incorporation of boron into the mesoporous framework of SBA-15 improves the surface characteristics, viz. surface acidity, support metal interaction and textural properties, necessary for efficient catalytic HDS reaction. The catalysts BSM and BSMC outperformed their analogous catalysts SM and SMC. The catalytic efficiency of BSMC is outstanding and capable of desulfurizing diesel fuel (1000 ppmw-S) containing a more complex matrix with a 90% conversion of methyldibenzothiophene (MDBT). BSMC possessed favorable and lower activation energy (Ea) of 77.11 kJ mol?1 than other catalysts and can be used as a commercial catalyst for ultradeep desulfurization of real fuel. Graphic abstract: [Figure not available: see fulltext.].
- Ganiyu, Saheed A.
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p. 3751 - 3768
(2021/05/11)
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- Selective C-O Bond Reduction and Borylation of Aryl Ethers Catalyzed by a Rhodium-Aluminum Heterobimetallic Complex
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We report the catalytic reduction of a C-O bond and the borylation by a rhodium complex bearing an X-Type PAlP pincer ligand. We have revealed the reaction mechanism based on the characterization of the reaction intermediate and deuterium-labeling experiments. Notably, this novel catalytic system shows steric-hindrance-dependent chemoselectivity that is distinct from conventional Ni-based catalysts and suggests a new strategy for selective C-O bond activation by heterobimetallic catalysis.
- Hara, Naofumi,Nakao, Yoshiaki,Saito, Teruhiko,Seki, Rin
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p. 6388 - 6394
(2021/05/31)
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- Ceramic boron carbonitrides for unlocking organic halides with visible light
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Photochemistry provides a sustainable pathway for organic transformations by inducing radical intermediates from substrates through electron transfer process. However, progress is limited by heterogeneous photocatalysts that are required to be efficient, stable, and inexpensive for long-term operation with easy recyclability and product separation. Here, we report that boron carbonitride (BCN) ceramics are such a system and can reduce organic halides, including (het)aryl and alkyl halides, with visible light irradiation. Cross-coupling of halides to afford new C-H, C-C, and C-S bonds can proceed at ambient reaction conditions. Hydrogen, (het)aryl, and sulfonyl groups were introduced into the arenes and heteroarenes at the designed positions by means of mesolytic C-X (carbon-halogen) bond cleavage in the absence of any metal-based catalysts or ligands. BCN can be used not only for half reactions, like reduction reactions with a sacrificial agent, but also redox reactions through oxidative and reductive interfacial electron transfer. The BCN photocatalyst shows tolerance to different substituents and conserved activity after five recycles. The apparent metal-free system opens new opportunities for a wide range of organic catalysts using light energy and sustainable materials, which are metal-free, inexpensive and stable. This journal is
- Yuan, Tao,Zheng, Meifang,Antonietti, Markus,Wang, Xinchen
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p. 6323 - 6332
(2021/05/19)
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- A facile and versatile electro-reductive system for hydrodefunctionalization under ambient conditions
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A general electrochemical system for reductive hydrodefunctionalization is described, employing the inexpensive and easily available triethylamine (Et3N) as a sacrificial reductant. This protocol is characterized by facile operation, sustainable conditions, and exceptionally wide substrate scope covering the cleavage of C-halogen, N-S, N-C, O-S, O-C, C-C and C-N bonds. Notably, the selectivity and capability of reduction can be conveniently switched by simple incorporation or removal of an alcohol as a co-solvent.
- Huang, Binbin,Guo, Lin,Xia, Wujiong
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supporting information
p. 2095 - 2103
(2021/03/26)
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- Experimental and theoretical studies on gold(iii) carbonyl complexes: reductive C,H- And C,C bond formation
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The reactivity of cationic (C^C)gold(iii) carbonyl complexes was investigated. While thein situ-formed IPrAu(bph)CO+complex (bph = biphenyl-2,2′-diyl) does not undergo a migratory insertion of CO into the neighboring gold-carbon bond, nucleophiles can attack the coordinated CO moiety intermolecularly. Water as a nucleophile initiates a CO2extrusion combined with a reductive C,H bond formation. The rapid formation of a gold(i) species from an intermediary gold(iii) carbonyl has not been observed before and shows a significant difference in reactivity between (C^C) and (C^N^C)gold(iii) carbonyls. The latter have been reported to form stable gold(iii) hydridesviathe WGS reaction. In the case of methanol acting as a nucleophile attacking the gold(iii) carbonyl, no extrusion of CO2is observed. Instead an intermediary gold(iii) carboxyl complex forms an aryl carboxylateviareductive C-C bond elimination. Experimental and theoretical studies on the mechanism explain the observed selectivities and give new insights into the reactivity of elusive gold(iii) carbonyls.
- Ahrens, Alexander,Dreuw, Andreas,Hashmi, A. S. K.,Hoffmann, Marvin,Karger, Leonhard F. P.,Lustosa, Danilo M.,Rudolph, Matthias
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p. 8752 - 8760
(2021/07/02)
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- Palladium-catalyzed denitrogenative cross-coupling of aryl halides with arylhydrazines under mild reaction conditions
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A greener approach for the synthesis of various functionalized biaryl frameworks in good to excellent yield through palladium-catalyzed denitrogenative cross-coupling of aryl halides with arylhydrazines under mild reaction conditions was developed. Catalytic system is free from the aid of expensive ligands and external oxidants. Biogenically prepared palladium nanoparticles (Pd NPs) immobilized cellulose based dip catalyst displayed excellent reactivity and selectivity toward the synthesis of a broad array of symmetrical and unsymmetrical biaryls through C–N bond cleavage in air as green oxidant. In addition, recyclability in denitrogenative cross-coupling reaction was also studied which showed excellent recycling performance and the dip catalyst remained stable even after several reuses. Thus, our newly developed strategy was successfully applied for constructing wide-ranging functional groups tolerated biaryls using arylhydrazines and aryl halides as coupling partners which is most useful for practical applications in synthetic chemistry.
- Kempasiddaiah, Manjunatha,Kandathil, Vishal,Dateer, Ramesh B.,Sasidhar,Patil, Shivaputra A.,Patil, Siddappa A.
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p. 273 - 281
(2021/01/12)
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- Ligand and Base Free Synthesis of Biaryls from Aryl Halides in Aqueous Media with Recyclable Ti0.97Pd0.03O1.97 Catalyst
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Abstract: Facile protocol for the synthesis of biaryls from aryl halides in presence of magnesium metal without prior formation of organometallic intermediate has been exploited. Irrespective of aqueous medium, Ti0.97Pd0.03O1.97 catalyst supports C–C bond formation reaction in presence of metals rather than dehalogenation without any additives. Homocoupling of 16 different aryl halides furnished corresponding biphenyls in good yield with better functional group tolerance. The recovery of the catalyst was carried out by employing catalyst coated cordierite monolith up to 7th cycle with high yields. A new approach for the cross-coupling reaction is also attempted. Graphic Abstract: [Figure not available: see fulltext.]
- Prasanna,Bhat, Shrikanth K.,Usha,Hegde
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p. 3313 - 3322
(2021/03/04)
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- Efficient photocatalytic chemoselective and stereoselective C-C bond formation over AuPd@N-rich carbon nitride
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Heterogeneous chemoselective or stereoselective C-C coupling reactions remain extremely challenging in traditional organic synthesis. Here, we constructed a AuPd@N-rich carbon nitride (NRCN) photocatalyst through simple ammonia solution heat treatment of carbon nitride and then AuPd NP loading. AuPd@NRCN exhibited extraordinary light color promoted catalytic performance in C-C bond formation under visible light in air. Surprisingly, both high chemoselectivity to unsymmetrical Ullmann biaryl products and satisfactory stereoselectivity to Z-type Heck reaction products could be achieved by changing the light source color. Various substrates exhibited great potential for the economical synthesis of unsymmetrical biaryl products and Z-type olefins. Efficient visible light promoted C-I bond activation accompanied with improved photocatalytic coupling reaction efficiency over AuPd@NRCN was verified firstly by in situ DRIFTS. Considering that the Ullmann cross-coupling reaction is a multi-photon reaction, the improved photocatalytic performance in the Ullmann cross-coupling reaction using a combination of light sources with different colors might be due to the activation of different substrates and/or steps requiring different energies, and the combination of the two energy sources was beneficial for improving the activation efficiency of different substrates and/or steps. The activation of iodobenzene and styrene in the Heck reaction with light was also beneficial to the formation of the stilbene product. The light color promoted chemoselectivity and stereoselectivity are expected to have profound impact on organic synthetic methodology improvement. This journal is
- Jiang, Heyan,Xu, Jie,Zhang, Sishi,Cheng, Hongmei,Zang, Cuicui,Bian, Fengxia
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p. 219 - 229
(2021/01/28)
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- Grignard reagent dictated copper(I) phosphines catalyzed reductive coupling of diazo compounds: The chemistry beyond carbene generation
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Copper-dppf catalyzed reductive coupling of diazo compounds through terminal nitrogen is reported. However, copper catalysts are known to produce carbene from diazo compounds; the reaction conditions played an important role in the formation of diazine over carbene generation. Several control experiments have been conducted to understand the reaction mechanism and found that the formation of a copper–Mg heterobimetallic complex would be responsible for the observed reactivity pattern. The reaction produced diazine as a reductive coupling product along with biphenyl as a by-product. All the synthesized diazines have been characterized fully by using analytical and spectroscopic techniques.
- Kuzhalmozhi Madarasi, Packirisamy,Sivasankar, Chinnappan
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- C-C Bond Elimination from High-Valent Mn Aryl Complexes
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Manganese complexes have been considered as a cheap and readily available alternative to commonly used precious metal catalysts in C-C bond coupling reactions. Although high-valent Mn aryl intermediates have been proposed in such reactions, a mechanistic understanding of possible organometallic intermediates in Mn-mediated C-C coupling is still lacking due to their high reactivity. We report the synthesis of stable, isolable Mn(III) aryl complexes obtained by oxidative addition of aryl bromide or aryl chloride. These complexes react with a range of organometallic alkylating or arylating reagents (alkyl and aryl Grignard reagents, MeLi, ZnMe2) to undergo C(sp2)-C(sp3) or C(sp2)-C(sp2) bond coupling, and a preliminary catalytic system could be demonstrated. The reagent scope and yield of the C(sp2)-C(sp3) coupled product can further be increased by addition of TEMPO as an oxidant, generating alkyl radicals.
- He, Yu-Tao,Karimata, Ayumu,Gladkovskaya, Olga,Khaskin, Eugene,Fayzullin, Robert R.,Sarbajna, Abir,Khusnutdinova, Julia R.
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supporting information
p. 2320 - 2331
(2021/05/06)
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- Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**
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Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover a new electron-primed photoredox catalyst capable of promoting the reductive cleavage of strong C(sp2)?N and C(sp2)?O bonds. We illustrate several examples of the synthetic utility of these deeply reducing but otherwise safe and mild catalytic conditions. Finally, we employ electrochemical current measurements to perform a reaction progress kinetic analysis. This technique reveals that the improved activity of this new system is a consequence of an enhanced catalyst stability profile.
- Chernowsky, Colleen P.,Chmiel, Alyah F.,Wickens, Zachary K.
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supporting information
p. 21418 - 21425
(2021/08/25)
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- Synthesis of arylboronates via the Pd-catalyzed desulfitative coupling reaction of sodium arylsulfinates with bis(pinacolato)diboron
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The desulfitative borylation reaction of sodium arylsulfinates with bis(pinacolato)diboron or bis(neopentylglycolato)diboron under palladium catalysis has been developed, allowing selective C-B bond formation to give arylboronates with a range of functional groups in moderate to good yields under mild reaction conditions. A gram-scale preparation as well as the cascade Suzuki-Miyaura cross-coupling of arylboronates demonstrated the potential practical utility in organic synthesis.
- Qiu, Di,Li, Songyi,Yue, Guanglu,Mao, Jinshan,Xu, Bei,Yuan, Xinyu,Ye, Fei
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- Reduced Phenalenyl in Catalytic Dehalogenative Deuteration and Hydrodehalogenation of Aryl Halides
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Dehalogenative deuteration reactions are generally performed through metal-mediated processes. This report demonstrates a mild protocol for hydrodehalogenation and dehalogenative deuteration of aryl/heteroaryl halides (39 examples) using a reduced odd alternant hydrocarbon phenalenyl under transition metal-free conditions and has been employed successfully for the incorporation of deuterium in various biologically active compounds. The combined approach of experimental and theoretical studies revealed a single electron transfer-based mechanism.
- Singh, Bhagat,Ahmed, Jasimuddin,Biswas, Amit,Paira, Rupankar,Mandal, Swadhin K.
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supporting information
p. 7242 - 7255
(2021/05/29)
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- Electrochemical-Promoted Nickel-Catalyzed Oxidative Fluoroalkylation of Aryl Iodides
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This work describes a general strategy for metal-catalyzed cross-coupling of fluoroalkyl radicals with aryl halides under electrochemical conditions. The contradiction between anodic oxidation of fluoroalkyl sulfinates and cathodic reduction of low-valent nickel catalysts can be well addressed by paired electrolysis, allowing for direct introduction of fluorinated functionalities into aromatic systems.
- Zou, Zhenlei,Li, Heyin,Huang, Mengjun,Zhang, Weigang,Zhi, Sanjun,Wang, Yi,Pan, Yi
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supporting information
p. 8252 - 8256
(2021/11/01)
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- Dehalogenation reaction photocatalyzed by homoleptic copper(i) complexes associated with strongly reductive sacrificial donors
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In order to perform challenging reduction reactions with light, at low cost and low toxicity, we aim at using for the first time a reductive quenching cycle with a simple, strongly colored homoleptic copper(i) complex [Cu(dipp)2]+(dipp = 2,9-diisopropyl-1,10-phenanthroline). Complexes of this family being weak photo-oxidants, we specifically designed and synthesized powerful, recyclable sacrificial electron donors D. We demonstrate that, during irradiation with LED light in the presence of D, the strong reductant [Cu(dipp)2]0is efficiently photo-generated. Further, we present the first photochemical reaction using photo-generated [Cu(dipp)2]0and evidence that the kinetics of the overall reaction are strongly affected by the oxidation potential of the sacrificial donorE(D+/D). Adapting the thermodynamics of sacrificial donors D and [Cu(dipp)2]+has thus allowed us to unlock a brand new concept, giving access to cheap, non-toxic solar light-generated very strong reductive power.
- Blart, Errol,Gimeno, Lea,Mall Haidaraly, Kevin,Pellegrin, Yann,Queffélec, Clémence
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p. 6041 - 6047
(2021/09/28)
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- Copper-catalyzed meta-selective arylation of phenol derivatives: An easy access to m-aryl phenols
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Achieving selective meta-functionalization of phenols is a significant challenge. Accessing such compounds generally needs elevated temperature or incorporation of complex templates. Here, we report a general approach to achieve meta-arylated phenols with a simple and common directing group. This coppercatalyzed protocol proceeds with complete meta-selectivity and tolerates a variety of functional groups in both coupling partners. Computational studies have revealed that the reaction proceeded via a Heck-like pathway.
- Maraswami, Manikantha,Hirao, Hajime,Loh, Teck-Peng
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p. 2302 - 2309
(2021/02/20)
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- Pd-Catalyzed Oxidative Aminocarbonylation of Arylboronic Acids with Unreactive Tertiary Amines via C-N Bond Activation
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An efficient synthesis of tertiary amides from aryl boronic acids and inert tertiary amines through the oxidative carbonylation via C(sp3)-N bond activation is presented. This protocol significantly restricts the homocoupling biarylketone product. It involves the use of a homogeneous PdCl2/CuI catalyst and a heterogeneous Pd/C based catalyst, which promotes C(sp3)-N bond activation of tertiary amines with aryl boronic acids. This process represents a ligand-free, base-free, and recyclable catalyst along with an ideal oxidant like molecular oxygen.
- Kolekar, Yuvraj A.,Bhanage, Bhalchandra M.
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supporting information
p. 14028 - 14035
(2021/05/29)
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- Suzuki-Miyaura Csp2-Csp2Cross-Couplings Employing Nickel(II) Pincer Precatalysts: Mechanistic Investigations
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This study investigates the mechanism of Suzuki-Miyaura Csp2-Csp2cross-couplings facilitated by PCP-type nickel(II) pincer complexes. By employing a combination of standard experimental and theoretical methods, it is proposed that a nickel(I)/(III) cycle is involved in this reaction and single-electron pathways likely operate in this transformation.
- Ho, Curtis C.,Olding, Angus,Fuller, Rebecca O.,Canty, Allan J.,Lucas, Nigel T.,Bissember, Alex C.
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supporting information
p. 2305 - 2310
(2021/05/06)
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- Nickel-Catalyzed Intramolecular 1,2-Aryl Migration of Mesoionic Carbenes (iMICs)
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Intramolecular 1,2-Dipp migration of seven mesoionic carbenes (iMICAr) 2 a–g (iMICAr=ArC{N(Dipp)}2CHC; Ar=aryl; Dipp=2,6-iPr2C6H3) under nickel catalysis to give 1,3-imidazoles (IMDAr) 3 a–g (IMDAr=ArC{N(Dipp)CHC(Dipp)N}) has been reported. The formation of 3 indicates the cleavage of an N?CDipp bond and the subsequent formation of a C?CDipp bond in 2, which is unprecedented in NHC chemistry. The use of 3 in accessing super-iMICs (5) (S-iMIC=ArC{N(Dipp)N(Me)C(Dipp)}C) has been shown with selenium (6), gold (7), and palladium (8) compounds. The quantification of the stereoelectronic properties reveals the superior σ-donor strength of 5 compared to that of classical NHCs. Remarkably, the percentage buried volume of 5 (%Vbur=45) is the largest known amongst thus far reported iMICs. Catalytic studies show a remarkable activity of 5, which is consistent with their auspicious stereoelectronic features.
- Merschel, Arne,Glodde, Timo,Neumann, Beate,Stammler, Hans-Georg,Ghadwal, Rajendra S.
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supporting information
p. 2969 - 2973
(2020/12/14)
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- Cu(OTf)2-Mediated Cross-Coupling of Nitriles and N-Heterocycles with Arylboronic Acids to Generate Nitrilium and Pyridinium Products**
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Metal-catalyzed C–N cross-coupling generally forms C?N bonds by reductive elimination from metal complexes bearing covalent C- and N-ligands. We have identified a Cu-mediated C–N cross-coupling that uses a dative N-ligand in the bond-forming event, which, in contrast to conventional methods, generates reactive cationic products. Mechanistic studies suggest the process operates via transmetalation of an aryl organoboron to a CuII complex bearing neutral N-ligands, such as nitriles or N-heterocycles. Subsequent generation of a putative CuIII complex enables the oxidative C–N coupling to take place, delivering nitrilium intermediates and pyridinium products. The reaction is general for a range of N(sp) and N(sp2) precursors and can be applied to drug synthesis and late-stage N-arylation, and the limitations in the methodology are mechanistically evidenced.
- Bell, Nicola L.,Xu, Chao,Fyfe, James W. B.,Vantourout, Julien C.,Brals, Jeremy,Chabbra, Sonia,Bode, Bela E.,Cordes, David B.,Slawin, Alexandra M. Z.,McGuire, Thomas M.,Watson, Allan J. B.
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supporting information
p. 7935 - 7940
(2021/03/03)
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- Aerobic Cu and amine free Sonogashira and Stille couplings of aryl bromides/chlorides with a magnetically recoverable Fe3O4@SiO2 immobilized Pd(II)-thioether containing NHC
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Two value added C–C cross coupling reactions; Sonogashira and Stille couplings were achieved at milder conditions in the catalytic presence of a magnetically recoverable heterogeneous catalyst Fe3O4@SiO2@NHC^SPh-Pd(II). The catalyst was earlier reported for Suzuki-Miyaura reaction, and as an extension of its catalytic efficiency, the Stille and Sonogashira cross coupling reactions under aerobic condition has been explored in present report. The Sonogashira coupling of aryl bromides and terminal alkynes produced an excellent yield (~96% at 0.25 mol% Pd) of the desired coupling product under copper and amines free conditions. Moreover, an excellent Stille coupling of readily available and more latent aryl chlorides and trialkylstannane was obtained (yields up to 95% at 0.25 mol% Pd) in absence of toxic fluorides additives. The broad substrate scope of the catalyst for both the coupling reactions and the magnetically recoverable feature of catalyst make this reaction highly desirable for industrial applications of present heterogeneous catalysis.
- Khandaka, Himanshu,Sharma, Kamal Nayan,Joshi, Raj Kumar
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supporting information
(2021/02/20)
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- Nickel- and Palladium-Catalyzed Cross-Coupling Reactions of Organostibines with Organoboronic Acids
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A strategy for the formation of antimony-carbon bond was developed by nickel-catalyzed cross-coupling of halostibines. This method has been applied to the synthesis of various triaryl- and diarylalkylstibines from the corresponding cyclic and acyclic halostibines. This protocol showed a wide substrate scope (72 examples) and was compatible to a wide range of functional groups such as aldehyde, ketone, alkene, alkyne, haloarenes (F, Cl, Br, I), and heteroarenes. A successful synthesis of arylated stibine 3 a in a scale of 34.77 g demonstrates high synthetic potential of this transformation. The formed stibines (R3Sb) were then used for the palladium-catalyzed carbon–carbon bond forming reaction with aryl boronic acids [R?B(OH)2], giving biaryls with high selectivity, even the structures of two organomoieties (R and R′) are very similar. Plausible catalytic pathways were proposed based on control experiments.
- Zhang, Dejiang,Le, Liyuan,Qiu, Renhua,Wong, Wai-Yeung,Kambe, Nobuaki
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supporting information
p. 3104 - 3114
(2020/12/11)
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- Water-Dispersible Pd–N-Heterocyclic Carbene Complex Immobilized on Magnetic Nanoparticles as a New Heterogeneous Catalyst for Fluoride-Free Hiyama, Suzuki–Miyaura and Cyanation Reactions in Aqueous Media
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Abstract: Pd–N-heterocyclic carbine complex immobilized on magnetic nanoparticles is synthesized and characterized by different techniques such as FT-IR, XPS, TEM, EDX, FESEM, VSM, TGA, and ICP. The synthesized catalyst was used as a new water dispersible heterogeneous catalyst in the fluoride-free Hiyama, Suzuki–Miyaura and cyanation reactions in pure water. By this method, different types of biaryls and aryl nitriles were synthesized in good to high yields by the reaction of a variety of aryl iodides, bromides and chlorides with triethoxyphenylsilane, phenylboronic acid and K4[Fe(CN)6]·3H2O, respectively. The presence of sulfonates as hydrophilic groups on the surface of the catalyst confers a highly water dispersible, active and yet magnetically recoverable Pd catalyst. The possibility to perform the reaction in water as a green medium, ease of the catalyst recovery and reuse by magnetic separation, and the absence of any additives or co-solvents make this method as an eco-friendly and economical protocol for the synthesis of biaryl derivatives and aryl nitriles. Graphic Abstract: A new water dispersible heterogeneous Pd–N-heterocyclic carbene for the efficient fluoride-free Hiyama, Suzuki–Miyaura and cyanation reactions in pure water is developed.[Figure not available: see fulltext.].
- Chahkamali, Farhad Omarzehi,Sansano, José Miguel,Sobhani, Sara
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- Fe-MIL-101 modified by isatin-Schiff-base-Co: a heterogeneous catalyst for C-C, C-O, C-N, and C-P cross coupling reactions
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A metal-organic framework functionalized with a cobalt-complex is preparedviapost-synthetic modification of Fe-MIL-101-NH2. Initially, Fe-MIL-101-NH2reacted with isatin to produce Fe-MIL-101-isatin-Schiff-base, which can anchor the cobalt by the addition of cobalt acetate. The resulting MOF-Co catalyst is characterized by employing multiple techniques. This new modified MOF acts as a heterogeneous and recyclable catalyst for efficient Ullmann, Buchwald-Hartwig, Hirao, Hiyama and Mizoroki-Heck cross-coupling reactions of several aryl halides/phenylboronic acid/phenyltosylate with phenols, anilines/heterocyclic amines, triethyl phosphite, triethoxyphenylsilane and alkenes and generates the expected coupling products in good to high yields.
- Farrokhi, Alireza,Rouzifar, Majid,Sansano, José Miguel,Sobhani, Sara
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p. 19963 - 19976
(2021/11/12)
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- Lipids as versatile solvents for chemical synthesis
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Development of safe, renewable, cheap and versatile solvents is a longstanding challenge in chemistry. We show here that vegetable oils and related systems can become prominent solvents for organic synthesis. Suzuki-Miyaura, Hiyama, Stille, Sonogashira and Heck cross-couplings proceed with quantitative yields in a range of vegetable oils, fish oil, butter and waxes used as solvents. Appropriate methodologies for high-throughput screening and sustainable isolation techniques applicable for vegetable oils and related lipids are presented.
- Bayer, Annette,Gevorgyan, Ashot,Hopmann, Kathrin H.
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supporting information
p. 7219 - 7227
(2021/09/28)
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- A new Pd(II)-supported catalyst on magnetic SBA-15 for C-C bond formation via the Heck and Hiyama cross-coupling reactions
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Magnetic mesoporous silica composite (MNP@SiO2-SBA) was obtained via embedding magnetite nanoparticles between SBA-15 channels. It was silylated with N-(3-(trimethoxysilyl)propyl)picolinamide (TMS-PCA) and then complexed with Pd(II). The obtained supported Pd(II) catalyst (MNP@SiO2-SBA-PCA) was characterized by conventional methods. The prepared magnetic catalyst showed high activity in the Heck and Hiyama reactions under optimal reaction conditions, including solvent, amount of catalyst, base, and temperature. Aryl bromides and iodides showed better results than aryl chlorides, and the catalyst exhibited noticeable stability and reused several times.
- Rahimi, Leila,Mansoori, Yagoub,Nuri, Ayat,Koohi-Zargar, Behzad,Esquivel, Dolores
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- Pd-catalyzed oxidative homocoupling of arylboronic acids in WEPA: A sustainable access to symmetrical biaryls under added base and ligand-free ambient conditions
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Symmetrical and unsymmetrical biaryls comprises a diverse class of biologically eloquent organic compounds. We herein report, a quick and eco-friendly protocol for the synthesis of biaryls by an oxidative (aerobic) homocoupling of arylboronic acids (ABAs) using Pd(OAc)2 in water extract of pomogranate ash (WEPA) as an efficient agro-waste(bio)-derived aqueous (basic) media. The reactions were executed at ambient aerobic conditions in the absence of external base and ligand to result symmetrical biaryls in excellent yields. The use of renewable media with an effective exploitation of waste, short reaction times, excellent yields of products, easy separation of the products, unnecessating the external base, oxidant, ligand or volatile organic solvents and ambient reaction conditions are the vital insights of the present protocol.
- Appa, Rama Moorthy,Lakshmidevi, Jangam,Naidu, Bandameeda Ramesh,Venkateswarlu, Katta
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- Copper-Catalysed Electrophilic Amination of Aryl(alkenyl) Boronic Acids with Nitrogen-Containing Hypervalent Iodine (III) Reagent
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A copper-catalysed electrophilic N-imination of aryl(alkenyl) boronic acids with a stable hypervalent iodine(III) reagent containing a transferable (diarylmethylene)amino group is developed. The electrophilic C?N cross-coupling reaction proceeds smoothly at room temperature under oxidant-free and base-free conditions, which is further characterized by the broad functional group compatibility, thereof, extending the N-electrophile scope of electrophilic C?N cross-coupling outside the limitation of N?O and N?Cl reagents. (Figure presented.).
- Hu, Yuanyuan,Zheng, Songlin,Fan, Wu,Yuan, Weiming
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supporting information
p. 4701 - 4707
(2021/08/23)
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- Porphyrin n-pincer pd(Ii)-complexes in water: A base-free and nature-inspired protocol for the oxidative self-coupling of potassium aryltrifluoroborates in open-air
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Metalloporphyrins (and porphyrins) are well known as pigments of life in nature, since representatives of this group include chlorophylls (Mg-porphyrins) and heme (Fe-porphyrins). Hence, the construction of chemistry based on these substances can be based on the imitation of biological systems. Inspired by nature, in this article we present the preparation of five different porphyrin, meso-tetraphenylporphyrin (TPP), meso-tetra(p-anisyl)porphyrin (TpAP), tetra-sodium meso-tetra(p-sulfonatophenyl)porphyrin (TSTpSPP), meso-tetra(m-hydroxyphenyl)porphyrin (TmHPP), and meso-tetra(m-carboxyphenyl)porphyrin (TmCPP) as well as their N-pincer Pd(II)-complexes such as Pd(II)-meso-tetraphenylporphyrin (PdTPP), Pd(II)-meso-tetra(p-anisyl)porphyrin (PdTpAP), Pd(II)-tetrasodium meso-tetra(p-sulfonatophenyl)porphyrin (PdTSTpSPP), Pd(II)-meso-tetra(m-hydroxyphenyl)porphyrin (PdTmHPP), and Pd(II)-meso-tetra(m-carboxyphenyl)porphyrin (PdTmCPP). These porphyrin N-pincer Pd(II)-complexes were studied and found to be effective in the base-free self-coupling reactions of potassium aryltrifluoroborates (PATFBs) in water at ambient conditions. The catalysts and the products (symmetrical biaryls) were characterized using their spectral data. The high yields of the biaryls, the bio-mimicking conditions, good substrate feasibility, evading the use of base, easy preparation and handling of catalysts, and the application of aqueous media, all make this protocol very attractive from a sustainability and cost-effective standpoint.
- Hanafiah, Marlia M.,Lakkaboyana, Sivarama Krishna,Lakshmidevi, Jangam,Marella, Ravi Kumar,Naidu, Bandameeda Ramesh,Prasad, Sana Siva,Venkateswarlu, Katta
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- Effect of Alkyl Structures on the Anti-stacking and Anchoring of Pd/Diamine-Functionalized Graphene Nanoparticles in Application in Suzuki Reaction
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Three diamines (1,8-diaminooctane/p-phenylenediamine/biphenylenediamine) with different alkyl groups were used to synthesize the functionalized graphene networks. Pd as the common metal catalyst was used to explore the effects of alkyl types of diamines on anti-stacking, metal anchoring ability of functional graphene and hence the catalytic performance. The results were discussed by characterization of the material and its catalytic properties. All catalysts showed excellent catalytic performance on the Suzuki cross-coupling reaction with a high yield of up to 100%. The p-phenylenediamine and biphenylenediamine functionalized graphene with larger specific surface area was beneficial to improve the stability of the graphene catalyst and maintain good catalytic activity after 5 cycles. The Pd nanoparticles in 1,8-octanediamine materials have smaller size and a smaller loading with the same or even better catalytic performance than p-phenylenediamine, biphenylenediamine materials, due to the stronger electron donating ability of N of octanediamine than that of p-phenylenediamine.
- Tian, Yinbing,Tang, Zijie,Ru, Yu,Wang, Yuanyuan,Dai, Liyi
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p. 2745 - 2754
(2021/08/09)
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- Surface engineered Iridium-based magnetic photocatalyst paving a path towards visible light driven C-H arylation and cyanation reaction
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The report presents the fabrication and application of a highly versatile, magnetic and robust iridium based photoredox nanocatalyst. Herein, Ir(PPy)3 based photocatalyst sites have been chemically engineered over the magnetic nanoparticles to encompass the captivating features of homogeneous iridium photocatalyst with the magnetically recyclable core. A household photoreactor was designed and fabricated to achieve highly selective visible light driven oxidative C-H arylation and C-H cyanation under sustainable and ambient reaction conditions utilizing the Ir@PyBz@ASMNPs photoredox nanocatalyst. The environment friendly Ir@PyBz@ASMNPs shows excellent photocatalytic activity, broad substrate adaptability and outstanding recyclability compared to the analogous homogeneous catalysts. Indeed, the Ir@PyBz@ASMNPs possess some key features including high surface area, high iridium metal loading and excellent stability. This work is expected to enlighten and provide new insights in the rational design of high performance and recoverable photoredox nanocatalyst through surface engineering strategy.
- Gaur, Rashmi,Gawande, Manoj B.,Kaushik, Bhawna,Rana, Pooja,Sharma, Priti,Sharma, Rakesh K.,Yadav, Priya,Yadav, Sneha
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p. 297 - 308
(2021/08/23)
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- C–H Arylation of Benzene with Aryl Halides using H2 and a Water-Soluble Rh-Based Electron Storage Catalyst
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This paper reports the first example of C?H arylation of benzene under mild conditions, using H2 as an electron source {turnover numbers (TONs)=0.7–2.0 for 24 h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H2 is inactive during the radical transfer step, greatly reducing unwanted side reactions.
- Yatabe, Takeshi,Tome, Tamon,Takahashi, Yukina,Matsumoto, Takahiro,Yoon, Ki-Seok,Nakai, Hidetaka,Ogo, Seiji
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supporting information
p. 17326 - 17330
(2021/10/29)
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- Efficient visible-light-driven Suzuki coupling reaction over Co-doped BiOCl/Ce-doped Bi2O2CO3composites
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Suzuki coupling reaction is a widely practiced protocol in organic synthesis for the formation of C-C bonds. The conventional process for this reaction usually involves high temperatures and noble metals. Hence, the development of a green, cost-effective photocatalytic system is an attractive and challenging strategy for the reaction. Here, we report a modified palladium-free Co-doped BiOCl/Ce-doped Bi2O2CO3(CBCB) composite, which shows high photocatalytic activity under white LED irradiation. At room temperature, an excellent yield (91%) of the desired cross-coupling product biphenyl was obtained in environmentally friendly solvents. Density functional calculations, together with the experimental results, show that the presence of Co and Ce ions results in the appearance of some impurity levels near the Fermi level of pure BiOCl and Bi2O2CO3, which decreases their forbidden bandwidth, thus ensuring higher light absorption and superior electronic conductivity. Moreover, the intimate interfacial contact between Co-doped BiOCl and Ce-doped Bi2O2CO3planes has a significant impact on the separation and transfer of photoinduced charge carriers, which ultimately leads to a remarkable increase in visible-light-driven photocatalytic activity.
- Zhao, Dan-Xia,Lu, Guo-Ping,Cai, Chun
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supporting information
p. 1823 - 1833
(2021/03/09)
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- Preparation of Ni-microsphere and Cu-MOF using aspartic acid as coordinating ligand and study of their catalytic properties in Stille and sulfoxidation reactions
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In this study, the thermal and catalytic behavior of Ni-microsphere and Cu-MOF were investigated with aspartic acid as the coordinating ligand with different morphologies. The Ni-microsphere and Cu-MOF with aspartic acid, as the coordinating ligand, were prepared via a solvothermal method. The morphology and porosity of the obtained Ni microsphere and Cu-MOF were characterized by XRD, FTIR, TGA, DSC, BET and SEM techniques. The catalytic activity of the Ni-microsphere and Cu-MOF was examined in Stille and sulfoxidation reactions. The Ni microsphere and Cu-MOF were easily isolated from the reaction mixtures by simple filtration and then recycled four times without any reduction of catalytic efficiency.
- Ghorbani-Choghamarani, Arash,Bastan, Hosna,Kakakhani, Zahra,Taherinia, Zahra
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p. 14905 - 14914
(2021/05/19)
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- Synthesis and Reactivity of (N2P2)Ni Complexes Stabilized by a Diphosphonite Pyridinophane Ligand
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A series of (N2P2)NiIIcomplexes (N2P2 =P,P′-ditertbutyl-2,11-diphosphonito[3.3](2,6)pyridinophane) stabilized by a modified tetradentate pyridinophane ligand containing two phosphonite groups were synthesized and characterized. Cyclic voltammetry (CV) studies revealed the accessibility of the NiIoxidation state at moderate redox potentials for these NiIIcomplexes.In situEPR, low-temperature UV-vis, and electrochemical studies were employed to detect the formation of NiIspecies during the reduction of NiIIprecursors. Furthermore, the [(N2P2)NiI(CNt-Bu)](SbF6) complex was isolated upon reduction of the NiIIprecursor with 1 equiv of CoCp2and was characterized by EPR and X-ray photoelectron spectroscopy (XPS). Finally, the (N2P2)NiIIBr2complex acts as an efficient catalyst for the Kumada cross-coupling of an aryl halide with an aryl or alkyl Grignard, suggesting that the N2P2 ligand can support the various Ni species involved in the catalytic C-C bond formation reactivity.
- Fuchigami, Kei,Watson, Michael B.,Tran, Giang N.,Rath, Nigam P.,Mirica, Liviu M.
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supporting information
p. 2283 - 2289
(2021/05/06)
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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- Amido PNP pincer complexes of palladium(II) and platinum(II): Synthesis, structure, and reactivity
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The synthesis of a series of divalent palladium and platinum complexes containing amido PNP pincer ligands of the type [N(o-C6H4PR2)2]? (R = Ph (1a), iPr (1b)) is reported. Metathetical reactions of [1a–b]PdCl or [1a–b]PtCl with a variety of alkyl Grignard reagents or LiHBEt3 in ethereal or arene solutions generate their corresponding alkyl or hydride complexes [1a]PdR1 (R1 = Me, Et, nBu), [1b]PdR1 (R1 = Me, Et, H), [1a]PtR1 (R1 = Me, Et, nBu, nHexyl, H), and [1b]PtR1 (R1 = Me, H). Although these organometallic complexes are all thermally stable, including those containing β-hydrogen atoms even at elevated temperatures, compounds [1a]PdH and [1b]PtR1 (R1 = Et, nBu, nHexyl) are not isolable due to facile decomposition. The stability and reactivity of these complexes are discussed. The chloro [1a]PdCl is a superior catalyst precursor to [1b]PdCl, [1a]PtCl, and [1b]PtCl in Kumada couplings, affording, for instance, n-butyl arenes nearly quantitatively. The X-ray structures of [1b]PtCl, [1b]PtMe, [1b]PdEt, [1a]PtnBu, [1b]PdH, and [1b]PtH are presented.
- Huang, Mei-Hui,Lee, Wei-Ying,Zou, Xue-Ru,Lee, Chia-Chin,Hong, Sheng-Bo,Liang, Lan-Chang
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