Xn:Harmful;
12125-02-9Relevant articles and documents
Room-Temperature Catalytic Reduction of Aqueous Nitrate to Ammonia with Ni Nanoparticles Immobilized on an Fe3O4@n-SiO2@h-SiO2–NH2 Support
Rai, Rohit Kumar,Tyagi, Deepika,Singh, Sanjay Kumar
, p. 2450 - 2456 (2017)
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.
One-pot, room-temperature conversion of dinitrogen to ammonium chloride at a main-group element
Légaré, Marc-André,Bélanger-Chabot, Guillaume,Rang, Maximilian,Dewhurst, Rian D.,Krummenacher, Ivo,Bertermann, Rüdiger,Braunschweig, Holger
, p. 1076 - 1080 (2020)
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.].
Nitrogen reduction and functionalization by a multimetallic uranium nitride complex
Falcone, Marta,Chatelain, Lucile,Scopelliti, Rosario,?ivkovi?, Ivica,Mazzanti, Marinella
, p. 332 - 335 (2017)
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.
Cleavage of Dinitrogen from Forming Gas by a Titanium Molecular System under Ambient Conditions
González-Moreiras, Mariano,Mena, Miguel,Pérez-Redondo, Adrián,Yélamos, Carlos
, p. 3558 - 3561 (2017)
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.
Ammonia Synthesis by Hydrogenolysis of Titanium-Nitrogen Bonds Using Proton Coupled Electron Transfer
Pappas, Iraklis,Chirik, Paul J.
, p. 3498 - 3501 (2015)
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.
Dinitrogen activation upon reduction of a triiron(II) complex
Lee, Yousoon,Sloane, Forrest T.,Blondin, Genevive,Abboud, Khalil A.,Garca-Serres, Ricardo,Murray, Leslie J.
, p. 1499 - 1503 (2015)
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.
Ligand-Based Control of Single-Site vs. Multi-Site Reactivity by a Trichromium Cluster
Bartholomew, Amymarie K.,Juda, Cristin E.,Nessralla, Jonathon N.,Lin, Benjamin,Wang, SuYin Grass,Chen, Yu-Sheng,Betley, Theodore A.
, p. 5687 - 5691 (2019)
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.
Cluster Supported by Redox-Active o-Phenylenediamide Ligands and Its Application toward Dinitrogen Reduction
Liang, Qiuming,Demuth, Joshua C.,Radovi?, Aleksa,Wolford, Nikki J.,Neidig, Michael L.,Song, Datong
, p. 13811 - 13820 (2021)
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.
Dinitrogen activation by dihydrogen and a PNP-ligated titanium complex
Wang, Baoli,Luo, Gen,Nishiura, Masayoshi,Hu, Shaowei,Shima, Takanori,Luo, Yi,Hou, Zhaomin
, p. 1818 - 1821 (2017)
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.
Facile Dinitrogen and Dioxygen Cleavage by a Uranium(III) Complex: Cooperativity Between the Non-Innocent Ligand and the Uranium Center
Wang, Penglong,Douair, Iskander,Zhao, Yue,Wang, Shuao,Zhu, Jun,Maron, Laurent,Zhu, Congqing
, p. 473 - 479 (2021)
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.
