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.
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.
Erratum: Lessons learned and lessons to be learned for developing homogeneous transition metal complexes catalyzed reduction of N2 to ammonia (Journal of Organometallic Chemistry (2014) 752 (44-58))
Sivasankar, Chinnappan,Baskaran, Sambath,Tamizmani, Masilamani,Ramakrishna, Kankanala
, p. 74 - 74 (2014)
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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.
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.
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.
Oligo(ω-pentadecalactone) decorated magnetic nanoparticles
Razzaq, Muhammad Yasar,Behl, Marc,Frank, Ute,Koetz, Joachim,Szczerba, Wojciech,Lendlein, Andreas
, p. 9237 - 9243 (2012)
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.
Direct formation of [NH4]N3 from a pentazolate salt through single-crystal to single-crystal transformation
Yang, Chen,Sun, Chengguo,Zhang, Chong,Hu, Bingcheng
, p. 144 - 147 (2018)
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.
Dinitrogen Activation and Hydrogenation by C5Me4SiMe3-Ligated Di- And Trinuclear Chromium Hydride Complexes
Shima, Takanori,Yang, Jimin,Luo, Gen,Luo, Yi,Hou, Zhaomin
, p. 9007 - 9016 (2020)
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.
Infrared Spectroscopic Study of the Cryogenic Thin Film and Matrix-Isolated Complexes of TiCl4 with NH3 and (CH3)3N
Everhart, Jennifer B.,Ault, Bruce S.
, p. 4379 - 4384 (1995)
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.
Dinitrogen cleavage by a heterometallic cluster featuring multiple uranium-rhodium bonds
Xin, Xiaoqing,Douair, Iskander,Zhao, Yue,Wang, Shuao,Maron, Laurent,Zhu, Congqing
, p. 15004 - 15011 (2020)
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.
CLUSTER BEAM CHEMISTRY: ADDUCTS OF HYDROGEN HALIDES WITH AMMONIA CLUSTERS
Cheung, Jeffery T.,Dixon, David A.,Herschbach, Dudley R.
, p. 2536 - 2541 (1988)
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.
Efficient catalytic conversion of dinitrogen to N(SiMe3)3 Using a homogeneous mononuclear cobalt complex
Suzuki, Tatsuya,Fujimoto, Keisuke,Takemoto, Yoshiyuki,Wasada-Tsutsui, Yuko,Ozawa, Tomohiro,Inomata, Tomohiko,Fryzuk, Michael D.,Masuda, Hideki
, p. 3011 - 3015 (2018)
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.
Stepwise Reduction of Dinitrogen by a Uranium-Potassium Complex Yielding a U(VI)/U(IV) Tetranitride Cluster
?ivkovi?, Ivica,Barluzzi, Luciano,Douair, Iskander,Fadaei-Tirani, Farzaneh,Jori, Nadir,Maron, Laurent,Mazzanti, Marinella
supporting information, p. 11225 - 11234 (2021/08/03)
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.
