- Room-Temperature Catalytic Reduction of Aqueous Nitrate to Ammonia with Ni Nanoparticles Immobilized on an Fe3O4@n-SiO2@h-SiO2–NH2 Support
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Efficient and selective catalytic reduction of aqueous nitrate to ammonia was achieved over Ni nanoparticles immobilized on Fe3O4@n-SiO2@h-SiO2–NH2 [a magnetic hierarchical mesoporous amine-functionalized (M-HMAF) silica] by using hydrazine hydrate as a reducing agent. The high hierarchical mesoporous structure (surface area of 416 m2 g–1 and pore size of 3.7 nm) and Fe3O4 core (ca. 7 nm) of the M-HMAF silica support resulted in a high dispersion of Ni nanoparticles over the support and easy recovery of the catalyst, respectively. Interestingly, the Ni/M-HMAF silica catalyst exhibited an excellent catalytic turnover (275 mmol gmetal–1 h–1) compared with most of the existing catalysts for the conversion of nitrate ions at room temperature. The mechanistic study using UV/Vis spectroscopy revealed that the catalytic conversion of nitrate ions to ammonia proceeded through in situ generated nitrite ions. Subsequently, the ammonia produced from nitrate ions was isolated and analyzed by 1H and 15N NMR spectroscopy, whereas the N2 gas released as a byproduct of hydrazine was characterized by GC–MS.
- Rai, Rohit Kumar,Tyagi, Deepika,Singh, Sanjay Kumar
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- One-pot, room-temperature conversion of dinitrogen to ammonium chloride at a main-group element
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The industrial reduction of dinitrogen (N2) to ammonia is an energy-intensive process that consumes a considerable proportion of the global energy supply. As a consequence, species that can bind N2 and cleave its strong N–N bond under mild conditions have been sought for decades. Until recently, the only species known to support N2 fixation and functionalization were based on a handful of metals of the s and d blocks of the periodic table. Here we present one-pot binding, cleavage and reduction of N2 to ammonium by a main-group species. The reaction—a complex multiple reduction–protonation sequence—proceeds at room temperature in a single synthetic step through the use of solid-phase reductant and acid reagents. A simple acid quench of the mixture then provides ammonium, the protonated form of ammonia present in fertilizer. The elementary reaction steps in the process are elucidated, including the crucial N–N bond cleavage process, and all of the intermediates of the reaction are isolated. [Figure not available: see fulltext.].
- Légaré, Marc-André,Bélanger-Chabot, Guillaume,Rang, Maximilian,Dewhurst, Rian D.,Krummenacher, Ivo,Bertermann, Rüdiger,Braunschweig, Holger
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- Nitrogen reduction and functionalization by a multimetallic uranium nitride complex
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Molecular nitrogen (N2) is cheap and widely available, but its unreactive nature is a challenge when attempting to functionalize it under mild conditions with other widely available substrates (such as carbon monoxide, CO) to produce value-added compounds. Biological N2 fixation can do this, but the industrial Haber-Bosch process for ammonia production operates under harsh conditions (450 degrees Celsius and 300 bar), even though both processes are thought to involve multimetallic catalytic sites. And although molecular complexes capable of binding and even reducing N2 under mild conditions are known, with co-operativity between metal centres considered crucial for the N2 reduction step, the multimetallic species involved are usually not well defined, and further transformation of N2 -binding complexes to achieve N-H or N-C bond formation is rare. Haber noted, before an iron-based catalyst was adopted for the industrial Haber-Bosch process, that uranium and uranium nitride materials are very effective heterogeneous catalysts for ammonia production from N2. However, few examples of uranium complexes binding N2 are known, and soluble uranium complexes capable of transforming N2 into ammonia or organonitrogen compounds have not yet been identified. Here we report the four-electron reduction of N2 under ambient conditions by a fully characterized complex with two U iii ions and three K+ centres held together by a nitride group and a flexible metalloligand framework. The addition of H2 and/or protons, or CO to the resulting N24- complex results in the complete cleavage of N2 with concomitant N2 functionalization through N-H or N-C bond-forming reactions. These observations establish that a molecular uranium complex can promote the stoichiometric transformation of N2 into NH3 or cyanate, and that a flexible, electron-rich, multimetallic, nitride-bridged core unit is a promising starting point for the design of molecular complexes capable of cleaving and functionalizing N2 under mild conditions.
- Falcone, Marta,Chatelain, Lucile,Scopelliti, Rosario,?ivkovi?, Ivica,Mazzanti, Marinella
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- Cleavage of Dinitrogen from Forming Gas by a Titanium Molecular System under Ambient Conditions
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Simple exposure of a hexane solution of [TiCp*Me3] (Cp=η5-C5Me5) to an atmosphere of commercially available and inexpensive forming gas (H2/N2 mixture, 13.5–16.5 % of H2) at room temperature leads to the methylidene–methylidyne–nitrido cube-type complex [(TiCp*)4(μ3-CH)(μ3-CH2)(μ3-N)2] via dinitrogen cleavage. This paramagnetic compound reacts with [D1]chloroform to give the titanium(IV) methylidyne–nitrido species [(TiCp*)4(μ3-CH)2(μ3-N)2], whereas its one-electron oxidation with AgOTf or [Fe(η5-C5H5)2](OTf) (OTf=O3SCF3) yields the diamagnetic ionic derivative [(TiCp*)4(μ3-CH)(μ3-CH2)(μ3-N)2](OTf). The μ3-nitrido ligands of the methylidyne–nitrido cubane complex can be protonated with [LutH](OTf) (Lut=2,6-lutidine) or hydrogenated with NH3?BH3 to afford μ3-NH imido moieties.
- González-Moreiras, Mariano,Mena, Miguel,Pérez-Redondo, Adrián,Yélamos, Carlos
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- Ammonia Synthesis by Hydrogenolysis of Titanium-Nitrogen Bonds Using Proton Coupled Electron Transfer
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The catalytic hydrogenolysis of the titanium-amide bond in (η5-C5Me4SiMe3)2Ti(Cl)NH2 to yield free ammonia is described. The rhodium hydride, (η5-C5Me5)(py-Ph)RhH (py-Ph = 2-phenylpyridine), serves as the catalyst and promotes N-H bond formation via hydrogen atom transfer. The N-H bond dissociation free energies of ammonia ligands have also been determined for titanocene and zirconocene complexes and reveal a stark dependence on metal identity and oxidation state. In all cases, the N-H BDFEs of coordinated NH3 decreases by >40 kcal/mol from the value in the free gas phase molecule.
- Pappas, Iraklis,Chirik, Paul J.
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- Dinitrogen activation upon reduction of a triiron(II) complex
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Reaction of a trinuclear iron(II) complex, Fe3Br3L (1), with KC8 under N2 leads to dinitrogen activation products (2) from which Fe3(NH)3L (2-1; L is a cyclophane bridged by three β-diketiminate arms) was characterized by X-ray crystallography. 1HNMR spectra of the protonolysis product of 2 synthesized under 14N2 and 15N2 confirm atmospheric N2 reduction, and ammonia is detected by the indophenol assay (yield ～30%). IR and Mssbauer spectroscopy, and elemental analysis on 2 and 2-1 as well as the tri(amido)triiron(II) 3 and tri(methoxo)triiron 4 congeners support our assignment of the reduction product as containing protonated N-atom bridges.
- Lee, Yousoon,Sloane, Forrest T.,Blondin, Genevive,Abboud, Khalil A.,Garca-Serres, Ricardo,Murray, Leslie J.
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- Ligand-Based Control of Single-Site vs. Multi-Site Reactivity by a Trichromium Cluster
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The trichromium cluster (tbsL)Cr3(thf) ([tbsL]6?=[1,3,5-C6H9(NC6H4-o-NSitBuMe2)3]6?) exhibits steric- and solvation-controlled reactivity with organic azides to form three distinct products: reaction of (tbsL)Cr3(thf) with benzyl azide forms a symmetrized bridging imido complex (tbsL)Cr3(μ3-NBn); reaction with mesityl azide in benzene affords a terminally bound imido complex (tbsL)Cr3(μ1-NMes); whereas the reaction with mesityl azide in THF leads to terminal N-atom excision from the azide to yield the nitride complex (tbsL)Cr3(μ3-N). The reactivity of this complex demonstrates the ability of the cluster-templating ligand to produce a well-defined polynuclear transition metal cluster that can access distinct single-site and cooperative reactivity controlled by either substrate steric demands or reaction media.
- Bartholomew, Amymarie K.,Juda, Cristin E.,Nessralla, Jonathon N.,Lin, Benjamin,Wang, SuYin Grass,Chen, Yu-Sheng,Betley, Theodore A.
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- Cluster Supported by Redox-Active o-Phenylenediamide Ligands and Its Application toward Dinitrogen Reduction
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As prevalent cofactors in living organisms, iron-sulfur clusters participate in not only the electron-transfer processes but also the biosynthesis of other cofactors. Many synthetic iron-sulfur clusters have been used in model studies, aiming to mimic their biological functions and to gain mechanistic insight into the related biological systems. The smallest [2Fe-2S] clusters are typically used for one-electron processes because of their limited capacity. Our group is interested in functionalizing small iron-sulfur clusters with redox-active ligands to enhance their electron storage capacity, because such functionalized clusters can potentially mediate multielectron chemical transformations. Herein we report the synthesis, structural characterization, and catalytic activity of a diferric [2Fe-2S] cluster functionalized with two o-phenylenediamide ligands. The electrochemical and chemical reductions of such a cluster revealed rich redox chemistry. The functionalized diferric cluster can store up to four electrons reversibly, where the first two reduction events are ligand-based and the remainder metal-based. The diferric [2Fe-2S] cluster displays catalytic activity toward silylation of dinitrogen, affording up to 88 equiv of the amine product per iron center.
- Liang, Qiuming,Demuth, Joshua C.,Radovi?, Aleksa,Wolford, Nikki J.,Neidig, Michael L.,Song, Datong
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- Dinitrogen activation by dihydrogen and a PNP-ligated titanium complex
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The hydrogenolysis of the PNP-ligated titanium dialkyl complex {(PNP)Ti(CH2SiMe3)2} (1, PNP = N(C6H3-2-PiPr2-4-CH3)2) with H2 (1 atm) in the presence of N2 (1 atm) afforded a binuclear titanium side-on/end-on dinitrogen complex {[(PNP)Ti]2(μ2,η1,η2-N2)(μ2-H)2} (2) at room temperature, which upon heating at 60 °C with H2 gave a μ2-imido/μ2-nitrido/hydrido complex {[(PNP)Ti]2(μ2-NH)(μ2-N)H} (3) through the cleavage and partial hydrogenation of the N2 unit. The mechanistic aspects of the hydrogenation of the N2 unit in 2 with H2 have been elucidated by the density functional theory calculations.
- Wang, Baoli,Luo, Gen,Nishiura, Masayoshi,Hu, Shaowei,Shima, Takanori,Luo, Yi,Hou, Zhaomin
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- Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non-Innocent Ligand and the Uranium Center
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Activation of dinitrogen (N2, 78 %) and dioxygen (O2, 21 %) has fascinated chemists and biochemists for decades. The industrial conversion of N2 into ammonia requires extremely high temperatures and pressures. Herein we report the first example of N2 and O2 cleavage by a uranium complex, [N(CH2CH2NPiPr2)3U]2(TMEDA), under ambient conditions without an external reducing agent. The N2 triple bond breaking implies a UIII–PIII six-electron reduction. The hydrolysis of the N2 reduction product allows the formation of ammonia or nitrogen-containing organic compounds. The interaction between UIII and PIII in this molecule allows an eight-electron reduction of two O2 molecules. This study establishes that the combination of uranium and a low-valent nonmetal is a promising strategy to achieve a full N2 and O2 cleavage under ambient conditions, which may aid the design of new systems for small molecules activation.
- Wang, Penglong,Douair, Iskander,Zhao, Yue,Wang, Shuao,Zhu, Jun,Maron, Laurent,Zhu, Congqing
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- Synthesis of calcium carbonate in trace water environments
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Calcium carbonate (CaCO3) was synthesized from diverse water-free alcohol solutions, resulting in the formation of vaterite and calcite precipitates, or stable particle suspensions, with the dimensions and morphologies depending upon the conditions used. The obtained results shed light on the importance of solvation during crystallization of CaCO3 and open a novel synthetic route for its precipitation in organic solvents.
- Magnabosco, Giulia,Polishchuk, Iryna,Pokroy, Boaz,Rosenberg, Rose,C?lfen, Helmut,Falini, Giuseppe
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- Oligo(ω-pentadecalactone) decorated magnetic nanoparticles
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Hybrid magnetic nanoparticles (mgNP) with a magnetite core diameter of 10 ± 1 nm surface functionalized with oligo(ω-pentadecalactone) (OPDL) oligomers with Mn between 1300 and 3300 g mol-1 could be successfully prepared having OPDL grafted from 200 mg g-1 to 2170 mg g-1. The particles are dispersible in chloroform resulting in stable suspensions. Magnetic response against an external magnetic field proved the superparamagnetic nature of the particles with a low coercivity (Bc) value of 297 T. The combination of the advantageous superparamagnetism of the mgNP with the exceptional stability of OPDL makes these novel hybrid mgNP promising candidates as multifunctional building blocks for magnetic nanocomposites with tunable physical properties.
- Razzaq, Muhammad Yasar,Behl, Marc,Frank, Ute,Koetz, Joachim,Szczerba, Wojciech,Lendlein, Andreas
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- Catalytic Dinitrogen Reduction to Ammonia at a Triamidoamine–Titanium Complex
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Catalytic reduction of N2 to NH3 by a Ti complex has been achieved, thus now adding an early d-block metal to the small group of mid- and late-d-block metals (Mo, Fe, Ru, Os, Co) that catalytically produce NH3 by N2 reduction and protonolysis under homogeneous, abiological conditions. Reduction of [TiIV(TrenTMS)X] (X=Cl, 1A; I, 1B; TrenTMS=N(CH2CH2NSiMe3)3) with KC8 affords [TiIII(TrenTMS)] (2). Addition of N2 affords [{(TrenTMS)TiIII}2(μ-η1:η1-N2)] (3); further reduction with KC8 gives [{(TrenTMS)TiIV}2(μ-η1:η1:η2:η2-N2K2)] (4). Addition of benzo-15-crown-5 ether (B15C5) to 4 affords [{(TrenTMS)TiIV}2(μ-η1:η1-N2)][K(B15C5)2]2 (5). Complexes 3–5 treated under N2 with KC8 and [R3PH][I], (the weakest H+ source yet used in N2 reduction) produce up to 18 equiv of NH3 with only trace N2H4. When only acid is present, N2H4 is the dominant product, suggesting successive protonation produces [{(TrenTMS)TiIV}2(μ-η1:η1-N2H4)][I]2, and that extruded N2H4 reacts further with [R3PH][I]/KC8 to form NH3.
- Doyle, Laurence R.,Wooles, Ashley J.,Jenkins, Lucy C.,Tuna, Floriana,McInnes, Eric J. L.,Liddle, Stephen T.
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- Direct formation of [NH4]N3 from a pentazolate salt through single-crystal to single-crystal transformation
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In the area of polynitrogen anions, the only stable species synthesized as yet are the azide anion (N3?) and the pentazolate anion (cyclo-N5?). We here describe an unprecedented example of a spontaneous single-crystal to single-crystal transformation from the pentazolate salt [NH4]4[H3O]3(N5)6Cl to the known [NH4]N3 with concomitant release of N2 and H2O, which involves the cleavage of N–N bonds and a change in space group. This transformation is helpful for the understanding of the relationship between the long-known N3? and the recently synthesized cyclo-N5? polynitrogen anions.
- Yang, Chen,Sun, Chengguo,Zhang, Chong,Hu, Bingcheng
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- In Situ Derived Bi Nanoparticles Confined in Carbon Rods as an Efficient Electrocatalyst for Ambient N2Reduction to NH3
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Electrocatalytic N2 reduction is deemed as a prospective strategy toward low-carbon and environmentally friendly NH3 production under mild conditions, but its further application is still plagued by low NH3 yield and poor faradaic efficiency (FE). Thus, electrocatalysts endowing with high activity and satisfying selectivity are highly needed. Herein, Bi nanoparticles in situ confined in carbon rods (Bi NPs@CRs) are reported, which are fabricated via thermal annealing of a Bi-MOF precursor as a high-efficiency electrocatalyst for artificial NH3 synthesis with favorable selectivity. Such an electrocatalyst conducted in 0.1 M HCl achieves a high FE of 11.50% and a large NH3 yield of 20.80 μg h-1 mg-1cat. at -0.55 and -0.60 V versus reversible hydrogen electrode, respectively, which also possesses high electrochemical durability.
- Wang, Fengyi,Zhang, Longcheng,Wang, Ting,Zhang, Fang,Liu, Qian,Zhao, Haitao,Zheng, Baozhan,Du, Juan,Sun, Xuping
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- Dinitrogen Activation and Hydrogenation by C5Me4SiMe3-Ligated Di- And Trinuclear Chromium Hydride Complexes
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Activation of dinitrogen (N2) by well-defined metal hydrides is of much interest and importance, but studies in this area have remained limited to date. We report here N2 activation and hydrogenation by C5Me4SiMe3-ligated di- and trinuclear chromium polyhydride complexes. Hydrogenolysis of [Cp′Cr(μ-Me)2CrCp′] (Cp′ = C5Me4SiMe3) (1) with H2 in a dilute hexane solution under N2-free conditions affords the dichromium dihydride complex [Cp′Cr(μ-H)2CrCp′] (2), while hydrogenolysis of 1 in a concentrated solution or without solvent provides the trinuclear chromium tetrahydride complex [(Cp′Cr)3(μ3-H)(μ-H)3] (3). When the reaction is carried out in the presence of N2 in a dilute hexane solution, the tetranuclear diimide/dihydride complex [(Cp′Cr)4(μ3-NH)2(μ3-H)2] (4) is formed via N-N bond cleavage and N-H bond formation. The reaction of 2 with N2 at room temperature gives the tetranuclear imide/nitride/dihydride complex [(Cp′Cr)3(C5Me3(CH2)SiMe3)Cr(μ3-NH)(μ3-N)(μ-H)2] (5) via N2 cleavage and hydrogenation and C-H bond activation of a Cp methyl group. At -30 °C, the reaction of 2 with N2 affords the dinitride intermediate [(Cp′Cr)4(μ3-N)2(μ3-H)2] (6), which is quantitatively transformed to 5 at room temperature. Complex 5 reversibly converts to the stereoisomer 5′. The hydrogenation of a mixture of 5 and 5′ with H2 affords 4. The reaction of 3 with N2 proceeds at 100 °C to afford [(Cp′Cr)3(μ3-NH)2] (7). This transformation has also been investigated by DFT calculations. Both experimental and computational studies suggest that N2 incorporation into the chromium hydride cluster is involved in the rate-determining step. This work represents the first example of N2 cleavage and hydrogenation by well-defined chromium hydride complexes.
- Shima, Takanori,Yang, Jimin,Luo, Gen,Luo, Yi,Hou, Zhaomin
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- Evaluating Molecular Cobalt Complexes for the Conversion of N2 to NH3
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Well-defined molecular catalysts for the reduction of N2 to NH3 with protons and electrons remain very rare despite decades of interest and are currently limited to systems featuring molybdenum or iron. This report details the synthesis of a molecular cobalt complex that generates superstoichiometric yields of NH3 (>200% NH3 per Co-N2 precursor) via the direct reduction of N2 with protons and electrons. While the NH3 yields reported herein are modest by comparison to those of previously described iron and molybdenum systems, they intimate that other metals are likely to be viable as molecular N2 reduction catalysts. Additionally, a comparison of the featured tris(phosphine)borane Co-N2 complex with structurally related Co-N2 and Fe-N2 species shows how remarkably sensitive the N2 reduction performance of potential precatalysts is. These studies enable consideration of the structural and electronic effects that are likely relevant to N2 conversion activity, including the π basicity, charge state, and geometric flexibility.
- Del Castillo, Trevor J.,Thompson, Niklas B.,Suess, Daniel L. M.,Ung, Ga?l,Peters, Jonas C.
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- Infrared Spectroscopic Study of the Cryogenic Thin Film and Matrix-Isolated Complexes of TiCl4 with NH3 and (CH3)3N
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The matrix isolation technique and infrared spectroscopy have been usedto isolate and characterize for the first time the 1:1 complex of TiCl4with NH3. Intense spectral features at 440 and 457 cm**-1 were assignedto the Ti-Cl antisymmetric stretching modes in this complex; the NH3 symmetric deformation was observed above 1200 cm**-1, shifted over 200 cm**-1 from the parent band position. The spectra suggest a trigonal bipyramidal arrangement about the central titanium with the NH3 ligand in an axial position. A similar set of product bands was observed for the 1:1 complex of TiCl4 with (CH3)3N, a species which had been observed previously but not fully characterized. Cryogenic thin film experiments with subsequent warming led to the formation of the 1:1 complex and further reaction products, including the 1:2 complex and two or more amido and/or imido complexes.
- Everhart, Jennifer B.,Ault, Bruce S.
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- Degradation of the beta-blocker propranolol by electrochemical advanced oxidation processes based on Fenton's reaction chemistry using a boron-doped diamond anode
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The electro-Fenton (EF) and photoelectro-Fenton (PEF) degradation of solutions of the beta-blocker propranolol hydrochloride with 0.5 mmol dm -3 Fe2+ at pH 3.0 has been studied using a single cell with a boron-doped diamond (BDD) anode and an air diffusion cathode (ADE) for H2O2 electrogeneration and a combined cell containing the above BDD/ADE pair coupled in parallel to a Pt/carbon felt (CF) cell. This naphthalene derivative can be mineralized by both methods with a BDD anode. Almost overall mineralization is attained for the PEF treatments, more rapidly with the combined system due to the generation of higher amounts of hydroxyl radical from Fenton's reaction by the continuous Fe2+ regeneration at the CF cathode, accelerating the oxidation of organics to Fe(III)-carboxylate complexes that are more quickly photolyzed by UVA light. The homologous EF processes are less potent giving partial mineralization. The effect of current density, pH and Fe2+ and drug concentrations on the oxidation power of PEF process in combined cell is examined. Propranolol decay follows a pseudo first-order reaction in most cases. Aromatic intermediates such as 1-naphthol and phthalic acid and generated carboxylic acids such as maleic, formic, oxalic and oxamic are detected and quantified by high-performance liquid chromatography. The chloride ions present in the starting solution are slowly oxidized at the BDD anode. In PEF treatments, all initial N of propranolol is completely transformed into inorganic ions, with predominance of NH 4+ over NO3- ion.
- Isarain-Chávez, Eloy,Rodríguez, Rosa María,Garrido, José Antonio,Arias, Conchita,Centellas, Francesc,Cabot, Pere Lluís,Brillas, Enric
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- Dinitrogen cleavage by a heterometallic cluster featuring multiple uranium-rhodium bonds
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Reduction of dinitrogen (N2) is a major challenge for chemists. Cooperation of multiple metal centers to break the strong N2 triple bond has been identified as a crucial step in both the industrial and the natural ammonia syntheses. However, reports of the cleavage of N2 by a multimetallic uranium complex remain extremely rare, although uranium species were used as catalyst in the early Harber-Bosch process. Here we report the cleavage of N2 to two nitrides by a multimetallic uranium-rhodium cluster at ambient temperature and pressure. The nitride product further reacts with acid to give substantial yields of ammonium. The presence of uranium-rhodium bond in this multimetallic cluster was revealed by X-ray crystallographic and computational studies. This study demonstrates that the multimetallic clusters containing uranium and transition metals are promising materials for N2 fixation and reduction.
- Xin, Xiaoqing,Douair, Iskander,Zhao, Yue,Wang, Shuao,Maron, Laurent,Zhu, Congqing
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- Niobium-nitrides derived from nitrogen splitting
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The easy-to-prepare Nb(v) aryloxide complex [(ArO)2Nb(μ-Cl)Cl2]2 (OAr = 2,6-bis(diphenylmethyl)-4-tert-butylphenoxide) is a precursor to both Nb(iv), [trans-(ArO)2NbCl2(THF)2], and Nb(iii), K3[(ArO)4Nb2(μ-Cl)3Cl2], molecules. The Nb(iv) and (v) complexes readily split atmospheric nitrogen at room temperature and 1 atmosphere, under reducing conditions, to produce the low-coordinate nitride dimer [(ArO)2Nb(μ-N)]2 and its radical anion, K[(ArO)2Nb(μ-N)]2. This journal is
- Searles, Keith,Carroll, Patrick J.,Chen, Chun-Hsing,Pink, Maren,Mindiola, Daniel J.
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- CLUSTER BEAM CHEMISTRY: ADDUCTS OF HYDROGEN HALIDES WITH AMMONIA CLUSTERS
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A molecular beam of ammonia clusters (NH3)n, with n = 1, 2,..., 20 or more, was generated by expansion from a supersonic nozzle and crossed with a beam of hydrogen halides HX, with X = Cl, Br, or I.This produced adduct complexes (NH3)mHX with m as large as 15.No such comlexes were observed for scattering from other crossed beams, including Ar, Kr, O2, Cl2, CH3Br, CH2CF2, CCl2F2, CF3Cl, and CH3CHF2.The smallest complexes observed have m = 1 for HCl and HBr but m = 3 for HI.The mass spectra of the complexes also differ noticeably with respect to the regions showing substantial fragmentation; completion of the first solvation shell appears to reduce fragmentation.Together with thermochemical data, these observations suggest that for sufficiently large clusters the complex formation involves proton transfer (more facile as HCl HBr HI) and is driven by solvation of the resulting NH4+X- ion pair by the extra NH3 molecules in the reactant cluster.
- Cheung, Jeffery T.,Dixon, David A.,Herschbach, Dudley R.
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- Preparation of carboxyl group functionalized magnetite nanoparticles with high magnetization
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A new route of the emulsifier-free emulsion polymerization was performed to prepare surface-functionalized magnetic nanoparticles. The Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy images confirm the formation of poly methacrylic acid (PMAA) layers and the existence of free carboxylicacid groups on the surface of magnetite particles. The poly methacrylic acid layer thickness which is estimated by thermal gravity analysis (TGA) increases from 6.5 to 10.6 nm with increasing mass ratio of monomer to magnetite from 3/1 to 16/1. The increase in thickness of the polymer cover results in the decrease in magnetization saturation of polymeric coated magnetic particles. However this reduction of about 20 emu g-1 is impressive lower compared to that in the other studies with the presence of surfactants or emulsifiers.
- Hung, Nguyen Quang,Cuong, Nguyen Viet,Van Thang, Tran,Nguyen, Hoang Thi Kieu
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- Efficient catalytic conversion of dinitrogen to N(SiMe3)3 Using a homogeneous mononuclear cobalt complex
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Incorporation of the tridentate phosphine-enamidoiminophosphorane onto cobalt(II) produces tetrahedral Co(NpNPiPr)Cl, 1, which upon reduction under dinitrogen generates the T-shaped, paramagnetic Co(I) complex Co(NpNPiPr), 2. This paramagnetic T-shaped derivative is in equilibrium with the paramagnetic dinitrogen derivative Co(NpNPiPr)(N2), 3, which can be detected by IR and low-temperature UV-vis spectroscopy. Both 1 and 2 act as homogeneous catalysts for the conversion of molecular nitrogen into tris(trimethylsilyl)amine (N(SiMe3)3) (～200 equiv, quantified as NH4Cl after hydrolysis) in the presence of excess KC8 and Me3SiCl at low temperatures.
- Suzuki, Tatsuya,Fujimoto, Keisuke,Takemoto, Yoshiyuki,Wasada-Tsutsui, Yuko,Ozawa, Tomohiro,Inomata, Tomohiko,Fryzuk, Michael D.,Masuda, Hideki
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- Amidinate Supporting Ligands Influence Molecularity in Formation of Uranium Nitrides
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Uranium nitride complexes are attractive targets for chemists as molecular models for the bonding, reactivity, and magnetic properties of next-generation nuclear fuels, but these molecules are uncommon and can be difficult to isolate due to their high reactivity. Here, we describe the synthesis of three new multinuclear uranium nitride complexes, [U(BCMA)2]2(μ-N)(μ-κ1:κ1-BCMA) (7), [(U(BIMA)2)2(μ-N)(μ-NiPr)(K2(μ-η3:η3-CH2CHNiPr)]2 (8), and [U(BIMA)2]2(μ-N)(μ-κ1:κ1-BIMA) (9) (BCMA = N,N-bis(cyclohexyl)methylamidinate, BIMA = N,N-bis(iso-propyl)methylamidinate), from U(III) and U(IV) amidinate precursors. By varying the amidinate ligand substituents and azide source, we were able to influence the composition and size of these nitride complexes. 15N isotopic labeling experiments confirmed the bridging nitride moieties in 7-9 were formed via two-electron reduction of azide. The tetra-uranium cluster 8 was isolated in 99% yield via reductive cleavage of the amidinate ligands; this unusual molecule contains nitrogen-based ligands with formal 1-, 2-, and 3- charges. Additionally, chemical oxidation of the U(IV) precursor U(N3)(BCMA)3 yielded the cationic U(V) species [U(N3)(BCMA)3][OTf]. Magnetic susceptibility measurements confirmed a U(IV) oxidation state for the uranium centers in the three nitride-bridged complexes and provided a comparison of magnetic behavior in the structurally related U(III)-U(IV)-U(V) series U(BCMA)3, U(N3)(BCMA)3, and [U(N3)(BCMA)3][OTf]. At 240 K, the magnetic moments in this series decreased with increasing oxidation state, i.e., U(III) > U(IV) > U(V); this trend follows the decreasing number of 5f valence electrons along this series.
- Arnold, John,Booth, Corwin H.,Boreen, Michael A.,Hohloch, Stephan,Lohrey, Trevor D.,Minasian, Stefan G.,Moreau, Liane M.,Ouellette, Erik T.,Qiao, Yusen,Settineri, Nicholas S.,Straub, Mark D.
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- Nanoporous NiSb to Enhance Nitrogen Electroreduction via Tailoring Competitive Adsorption Sites
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Ambient nitrogen reduction reaction (NRR) is attracting extensive interest but still suffers from sluggish kinetics owing to competitive rapid hydrogen evolution and difficult nitrogen activation. Herein, nanoporous NiSb alloy is reported as an efficient electrocatalyst for N2 fixation, achieving a high ammonia yield rate of 56.9 μg h?1 mg?1 with a Faradaic efficiency of 48.0%. Density functional theory calculations reveal that in NiSb alloy, Ni favors N2 hydrogenation while the neighboring Sb separates active sites for proton and N2 adsorption, which optimizes the adsorption/desorption of intermediates and enables an energetically favorable NRR pathway. This work indicates promising electrocatalytic application of the alloys of 3d and p block metals toward the NRR and provides an intriguing strategy to enhance the reduction of inert molecules by restraining the competitive hydrogen adsorption.
- Fan, Guilan,Xu, Wence,Li, Jinhan,Chen, Jia-Liang,Yu, Meng,Ni, Youxuan,Zhu, Shengli,Su, Xun-Cheng,Cheng, Fangyi
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- Stepwise Reduction of Dinitrogen by a Uranium-Potassium Complex Yielding a U(VI)/U(IV) Tetranitride Cluster
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Multimetallic cooperativity is believed to play a key role in the cleavage of dinitrogen to nitrides (N3-), but the mechanism remains ambiguous due to the lack of isolated intermediates. Herein, we report the reduction of the complex [K2{[UV(OSi(OtBu)3)3]2(μ-O)(μ-η2:η2-N2)}], B, with KC8, yielding the tetranuclear tetranitride cluster [K6{(OSi(OtBu)3)2UIV}3{(OSi(OtBu)3)2UVI}(μ4-N)3(μ3-N)(μ3-O)2], 1, a novel example of N2 cleavage to nitride by a diuranium complex. The structure of complex 1 is remarkable, as it contains a unique uranium center bound by four nitrides and provides the second example of a trans-NUVIN core analogue of UO22+. Experimental and computational studies indicate that the formation of the U(IV)/U(VI) tetrauranium cluster occurs via successive one-electron transfers from potassium to the bound N24- ligand in complex B, resulting in N2 cleavage and the formation of the putative diuranium(V) bis-nitride [K4{[UV(OSi(OtBu)3)3]2(μ-O)(μ-N)2}], X. Additionally, cooperative potassium binding to the U-bound N24- ligand facilitates dinitrogen cleavage during electron transfer. The nucleophilic nitrides in both complexes are easily functionalized by protons to yield ammonia in 93-97% yield and with excess 13CO to yield K13CN and KN13CO. The structures of two tetranuclear U(IV)/U(V) bis- and mononitride clusters isolated from the reaction with CO demonstrate that the nitride moieties are replaced by oxides without disrupting the tetranuclear structure, but ultimately leading to valence redistribution.
- ?ivkovi?, Ivica,Barluzzi, Luciano,Douair, Iskander,Fadaei-Tirani, Farzaneh,Jori, Nadir,Maron, Laurent,Mazzanti, Marinella
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supporting information
p. 11225 - 11234
(2021/08/03)
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- Tripodal P3XFe-N2Complexes (X = B, Al, Ga): Effect of the Apical Atom on Bonding, Electronic Structure, and Catalytic N2-to-NH3Conversion
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Terminal dinitrogen complexes of iron ligated by tripodal, tetradentate P3X ligands (X = B, C, Si) have previously been shown to mediate catalytic N2-to-NH3 conversion (N2RR) with external proton and electron sources. From this set of compounds, the tris(phosphino)borane (P3B) system is most active under all conditions canvassed thus far. To further probe the effects of the apical Lewis acidic atom on structure, bonding, and N2RR activity, Fe-N2 complexes supported by analogous group 13 tris(phosphino)alane (P3Al) and tris(phosphino)gallane (P3Ga) ligands are synthesized. The series of P3XFe-N2[0/1-] compounds (X = B, Al, Ga) possess similar electronic structures, degrees of N2 activation, and geometric flexibility as determined from spectroscopic, structural, electrochemical, and computational (DFT) studies. However, treatment of [Na(12-crown-4)2][P3XFe-N2] (X = Al, Ga) with excess acid/reductant in the form of HBArF4/KC8 generates only 2.5 ± 0.1 and 2.7 ± 0.2 equiv of NH3 per Fe, respectively. Similarly, the use of [H2NPh2][OTf]/Cp*2Co leads to the production of 4.1 ± 0.9 (X = Al) and 3.6 ± 0.3 (X = Ga) equiv of NH3. Preliminary reactivity studies confirming P3XFe framework stability under pseudocatalytic conditions suggest that a greater selectivity for hydrogen evolution versus N2RR may be responsible for the attenuated yields of NH3 observed for P3AlFe and P3GaFe relative to P3BFe.
- Fajardo, Javier,Peters, Jonas C.
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supporting information
p. 1220 - 1227
(2021/02/05)
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- Method for producing glycine by mixed solvent method
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The invention provides a clean production process of glycine. An organic mixed solvent is used for producing glycine and a by-product ammonium chloride by combined production. The organic mixed solvent comprises methanol, ethanol, and dihydric alcohol solvents or dihydric alcohol derivative solvents. The mixed solvent is added into a glycine synthesis reactor, urotropine and chloroacetic acid are added, ammonia is added, and a mixed crystal solid of glycine and ammonium chloride is obtained. The mixed crystal solid is added into a mixed solvent for separation, the mixed solvent for separation is heated to 60-80 DEG C, after glycine crystal is filtered, the mixed solvent for separation is cooled to 0-20 DEG C, and an ammonium chloride solid is separated by centrifugation.
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Paragraph 0017
(2016/11/14)
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- 4-Hydroxyphenacyl Ammonium Salts: A Photoremovable Protecting Group for Amines in Aqueous Solutions
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Irradiation of N-protected p-hydroxyphenacyl (pHP) ammonium caged derivatives at 313 nm releases primary and secondary amines or ammonia in nearly quantitative yields via the photo-Favorskii reaction when conducted in acidic or neutral aqueous buffered media. The reaction efficiencies are strongly dependent on the pH with the most efficient and highest yields obtained when the pH of the media maintains the ammonium and p-hydroxyl groups as their conjugate acids. For example, the overall quantum yields of simple secondary amines release are 0.5 at acidic pH from 3.9 to 6.6 dropping to 0.1 at neutral pH 7.0 and 0.01 at pH 8.4. Speciation studies provide an acid-base profile that helps define the scope and limitations of the reaction. When the pKa of the ammonium group is lower than that of the phenolic hydroxyl group, as is the case for the α-amino-protected amino acids, the more acidic ammonium ion deprotonates as the media pH is changed from acidic toward neutral or basic, thus diminishing the leaving group ability of the amino group. This, in turn, lowers the propensity for the photo-Favorskii rearrangement reaction to occur and opens the reaction pathway to alternative competing photoreduction process.
- Bownik, Iwona,?ebej, Peter,Literák, Jaromír,Heger, Dominik,?imek, Zdeněk,Givens, Richard S.,Klán, Petr
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p. 9713 - 9721
(2015/10/12)
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- Pyridonate-Supported Titanium(III). Benzylamine as an Easy-To-Use Reductant
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The reaction of bis(3-phenyl-2-pyridonate)Ti(NMe2)2 with excess benzylamine leads to an unexpected reduction of the metal center from Ti(IV) to Ti(III). The reduced titanium species was isolated and revealed as tris(3-phenyl-2-pyrido
- Chong, Eugene,Xue, Wei,Storr, Tim,Kennepohl, Pierre,Schafer, Laurel L.
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supporting information
p. 4941 - 4945
(2015/11/09)
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- Dinuclear gold(i) dithio- and diselenophosph(in)ate complexes forming mononuclear gold(iii) oxidative addition complexes and reversible chemical reductive elimination products
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Dinuclear gold(i) dithio- and diselenophosph(in)ate complexes were prepared to serve as precursors for subsequent oxidative addition (OA) chemistry following reaction with mild oxidant iodine, I2. The new OA products circumvented the formation
- Lee, Yu-Chen,Lin, Yan-Ru,Liou, Bo-Yuan,Liao, Jian-Hong,Gusarova, Nina K.,Trofimov, Boris A.,Van Zyl, Werner E.,Liu
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p. 663 - 670
(2014/01/06)
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- Characteristics and properties of a novel in situ method of synthesizing mesoporous TiO2 nanopowders by a simple coprecipitation process without adding surfactant
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In situ synthesis of mesoporous TiO2 nanopowders using titanium tetrachloride (TiCl4) and NH4OH as initial materials has been successfully fabricated by a coprecipitation process without the addition of surfactant. Characteristics and properties of the mesoporous TiO2 nanopowders were investigated using differential scanning calorimetry/ thermogravimetry (DSC/TG), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Barrent-Joyner-Halenda (BJH) analyses, transmission electron microscopy (TEM), selected area electron diffraction (SAED) and high resolution TEM (HRTEM). The results of TG and XRD showed that the NH4Cl decomposed between 513 and 673 K. XRD results showed that the anatase TiO2 only contained a single phase when the calcination temperature of the precursor powder was less than 673 K. Whereas phases of anatase and rutile TiO2 coexist after calcining at 773 K for 2 h. The crystalline size of the anatase and rutile TiO2 was 14.3 and 26.6 nm, respectively, when the precursor powder was calcined at 773 K for 2 h. The BET and BJH results showed a significant increase in surface area and pore volumes when the NH4Cl was completely decomposed. The maximum values of BET specific surface area and volume were 172.8 m2/g and 0.392 cm3/g, respectively. The average pore sizes when calcination was at 473 and 773 K for 2 h were 3.8 and 14.0 nm, respectively.
- Yeh, Shang-Wei,Ko, Horng-Huey,Chiang, Hsiu-Mei,Chen, Yen-Ling,Lee, Jian-Hong,Wen, Chiu-Ming,Wang, Moo-Chin
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p. 107 - 116
(2014/07/08)
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- BIOCIDAL IRON OXIDE COATING, METHODS OF MAKING, AND METHODS OF USE
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Embodiments of the present disclosure include visible light antimicrobial materials comprising α-Fe2O3 nanostructures fabricated by electron beam evaporation, methods of making the antimicrobial materials, and methods of using the antimicrobial materials.
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Paragraph 0093
(2013/07/31)
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- A self-contained regeneration scheme for spent ammonia borane based on the catalytic hydrodechlorination of BCl3
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Recycling: A self-contained procedure for the recycling of BNH-waste, based on the three major steps: polymer break-up, amine supported catalytic hydrodehalogenation of boron halogens, and the base exchange in borane amine adducts, is developed (see picture). Beyond the original task of recycling spent ammonia borane, the process provides a new means to produce borohydride species efficiently, by the direct use of molecular hydrogen. Copyright
- Reller, Christian,Mertens, Florian O.R.L.
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p. 11731 - 11735
(2013/01/15)
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- A PROCESS FOR PREPARING N-(HYDROCARBYL) PHOSPHORIC OR THIOPHOSPHORIC TRIAMIDES
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The invention provides a process for preparing N-(hydrocarbyl)phosphoric or thiophosphoric triamides with substantially improved yields and purity. Two equivalents of hydrocarbylamine are used in the reaction with phosphoryl or thiophosphoryl chloride and then with ammonia in an aromatic solvent. The invention further relates to N-(hydrocarbyl)phosphopric or thiophosphoric triamides having the purity of at least 98 %.
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Page/Page column 11
(2010/05/13)
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- METHODS AND COMPOSITIONS FOR THE TREATMENT OF PAIN
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The invention features methods, kits, and compositions for the treatment of pain.
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Page/Page column 25
(2008/12/07)
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- PROCESS FOR PRODUCING N,N'-CARBONYLDIIMIDAZOLE
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The present invention provides a process for producing N,N'-carbonyldiimidazole, comprising: reacting phosgene, diphosgene, or triphosgene with imidazole in an inert solvent to produce N,N'-carbonyldiimidazole; to imidazole hydrochloride yielded as a by-product in the above step, adding a gaseous or liquid basic compound represented by the below-shown general formula (1) in an inert solvent to conduct neutralization reaction; and circulating the imidazole thus generated to use it as a starting material for N,N'-carbonyldiimidazole production. In the general formula (1), R 1 , R 2 , and R 3 each independently represents a hydrogen atom, a methyl group, or an ethyl group. The CDI produced by the production process of the invention is a compound useful in the fields of synthesis of pharmaceutical agents, synthesis of agricultural chemicals, peptide synthesis, and the like, e.g., intermolecular condensation reactions, intramolecular condensation reactions for synthesizing N-carboxylic anhydrides, production of activated esters, and the like. The compound is especially suitable for use in applications where colorlessness is required.
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Page/Page column 5
(2008/06/13)
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- PHARMACEUTICAL COMPOSITIONS CONTAINING THE PHOSPHOLIPASE INHIBITOR SODIUM 3-(2-AMINO-1,2-DIOXOETHYL)-2-ETHYL-1-PHENYLMETHYL)-1H-INDOL-4-YL]OXY]ACETATE
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A lyophilized pharmaceutical composition is described which contains Sodium [[3-(2-amino-1,2-dioxoethyl)-2-ethyl-1-phenylmethyl)-1H-indol-4-yl]oxy]acetate, a Solubilizer, and a Stabilizer. Such compositions are storage stable and readily dissolve in aqueous medium to give injectable solution for treatment of sepsis, etc.
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Page/Page column 5
(2010/02/14)
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