80937-33-3Relevant articles and documents
Adsorption and reactivity of nitrogen oxides (NO2, NO, N2O) on Fe-zeolites
Rivallan, Mickael,Ricchiardi, Gabriele,Bordiga, Silvia,Zecchina, Adriano
, p. 104 - 116 (2009)
Nitrous oxide decomposition and temperature programmed desorption tests on Fe-ZSM-5 and Fe-silicalite show that the catalytic conversion mechanism of N2O into N2 and O2 over Fe-zeolites is more complex than expected. Nitro
Tuning the O2 Binding Affinity of Cobalt(II) Centers by Changing the Structural and Electronic Properties of the Distal Substituents on Azole-Based Chelating Ligands
Nishiura, Toshiki,Chiba, Yosuke,Nakazawa, Jun,Hikichi, Shiro
, p. 14218 - 14229 (2018)
The effects of the substituents on the chelating ligands located in the secondary coordination sphere on the O2 affinity of cobalt(II) centers have been explored. The combination of facially capping tridentate tris(pyrazolyl)borates (= TpMe2,4R) and bidentate bis(imidazolyl)borates (= [B(ImN-Me)2MeX]- LX) yields square-pyramidal cobalt(II) complexes. The structural properties of the substituent groups X attached to the boron center of LX affect the arrangement of X in the resulting cobalt(II) complexes [CoII(TpMe2,4R)(LX)]. When the boron-attached moiety of X is a relatively bulky sp3-CH2Y group (i.e., X:Y = Me:H and nBu:nPr), the alkyl group X faces the cobalt center, whereas for isopropoxy (OiPr) and phenyl (Ph) groups, of which the boron-attached atoms are a less hindered oxygen atom and a planer sp2-carbon, respectively, the X group is arranged away from the cobalt center. This flexible behavior of LX is reflected in the O2 affinity of the cobalt(II) center, which depends on the extent to which the complex sphere is shielded by the ligands. The dependence of the cobalt(II) oxidation potential on the X substituent of LX is inconsistent with the O2 affinity. On the other hand, the electronic properties of R, which is attached to the fourth position of the pyrazolyl rings in the rigid TpMe2,4R ligand, are reflected in the electrochemical properties and O2 affinity of the cobalt center.
Decomposition of Nitrous Oxide on Palladium Crystal Planes
Eley, Daniel D.,Klepping, Anthony H.,Moore, Peter B.
, (1985)
The catalysed decomposition of N2O in the range 830 - 1000 K and 0.05 - 1.0 Torr (1 Torr ca. 133 Pa) has been examined on Pd single-crystal surfaces and polycrystalline wires and compared with earlier work.The relative reaction velocities at 1000 deg K an
Oxidatively induced reductive elimination of dioxygen from an η2-peroxopalladium(II) complex promoted by electron-deficient alkenes
Popp, Brian V.,Stahl, Shannon S.
, p. 2804 - 2805 (2006)
The first example of associative displacement of dioxygen from a peroxopalladium(II) complex is reported. Electron-deficient alkenes, p-X-trans-β-nitrostyrene (X = OCH3, CH3, H, F, Br, CF3, NO2), react quantitatively with (bc)Pd(η2-O2) (bc = bathocuproine) in dichloromethane at room temperature to form the corresponding palladium(0)-alkene complexes. Mechanistic studies indicate that ligand substitution proceeds through an associative mechanism, and the electronic characteristics of the reactions are consistent with an oxidatively induced reductive elimination pathway. Copyright
Reversible O2 binding to a dinuclear copper(I) complex with linked tris(2-pyridylmethyl)amine units: Kinetic-thermodynamic comparisons with mononuclear analogues
Lee, Dong-Heon,Wei, Ning,Murthy, Narasimha N.,Tyeklár, Zoltán,Karlin, Kenneth D.,Kaderli, Susan,Jung, Bernhard,Zuberbühler, Andreas D.
, p. 12498 - 12513 (1995)
The kinetics and thermodynamics of reaction of O2 with copper(I) complexes can provide fundamental information relevant to chemical and biological systems. Using diode-array variable-temperature (180-296 K) stopped-flow kinetic methods, we report detailed information on the O2 reactivity (in EtCN) of dicopper(I) complex [(D1)Cu(I)2(RCN)2]2+ (2a) (R = Me or Et) [D1 = dinucleating ligand with a -CH2CH2- group linking two tris(2-pyridylmethyl)amine (TMPA) units at a 5-pyridyl position of each tetradentate moiety]. A comparative study of mononuclear complex [(TMPAE)Cu(RCN)]+ (1a') [TMPAE has a -C(O)OCH3 ester substituent in the 5-position of one pyridyl group of TMPA] has been carried out. The results are compared with data from the previously investigated complex [(TMPA)Cu(RCN)]+ (1a). The syntheses of D1 and 2a-(ClO4)2 are described; an X-ray structure reveals two pentacoordinate Cu(I) ions (Cu···Cu = 11.70 A?), each bound by the N4-tetradentate and an EtCN molecule. Cyclic voltammetric data for 1a' and 2a are reported. At 193 K in EtCN, 2a reacts with O2 (Cd/C2 = 2:1, manometry) to produce an intensely purple colored solution of adduct [(D1)Cu2(O2)]2+ (2c), λ(max) = 540 nm (ε = 11 100 M-1 cm-1). This peroxo-dicopper(II) species reacts with PPh3, liberating O2 and producing the isolatable bis-phosphine adduct [(D1)Cu2(PPh3)2]2+. The kinetic investigation provides spectral characterization of transient Cu/O2 1:1 adducts generated upon oxygenation of cold solutions of 1a' or 2a. [(TMPAE)Cu(O2)]+ (1b') forms reversibly (λ(max) = 415 nm) with k1 = (8.2 ± 0.4) x 103 M-1 s-1 and K1 = k1/k-1 = (284 ± 9) M-1 at 183 K, with ΔH1° = (-32 ± 1) kJ mol-1, ΔS1° = (-127 ± 3) J K-1 mol-1. Two types of Cu(II)-O2- complexes form in the reaction of 2a: a 2:1 open form (i.e., [(D1)Cu2(O2)(EtCN)]2+, 2b) and a bis-O2 2:2 open adduct (i.e., [(D1)Cu2(O2)2]2+, 2b'). For the formation of 2b, k1 = (1.63 ± 0.01) x 104 M-1 s-1 and K1 = (2.03 ± 0.04) x 103 M-1 at 183 K. Complexes 2b and 2b' have identical spectroscopic properties (λ(max) = 416 nm, ? = 4500 M-1 cm-1) per Cu-O2 unit, and their rate constants are statistically related. Intermediates 1b' and 2b further convert into (μ-peroxo)dicopper(II) [(2 Cu):(1O2)] complexes. [{(TMPAE)Cu}2(O2)]2+ (1c') (λ(max) = 532 nm, ? = 9380 M-1 cm-1) forms in a second-order reaction of 1b' with 1a' with K1K2 = (2.1 ± 0.4) x 1011 M-2 at 183 K (ΔH12° = -77 ± 1 kJ mol-1 and AS12° = -203 ± 5 J K-1 mol-1), while [(D1)Cu2(O2)]2+ (2c) (λ(max) = 540 nm, ? = 11 100 M-1 cm-1) is generated from 2b in an intramolecular reaction,with k2 = (3.51 ± 0.05) x 101 s-1 and k(on) = k1k2/k-1 = (7.1 ± 0.2) x 104 M-1 s-1 (183 K). The overall formation of 2c is faster than for 1c' or [{(TMPA)Cu}2(O2)]2+ (1c) because of a more positive entropy of activation (ΔS(on)paragraph = (-139 ± 3) J K-1 mol-1 for 2c vs ΔS(on)paragraph = (-201 ± 5) J K-1 mol-1 for 1c). However, this significantly enhanced kinetic reactivity (for 2a → 2c) is not reflected by an analogous increase in thermodynamic stability. [(D1)Cu2(O2)]2+ (2c) is enthalpically less stable (ΔH12° = (-34.8 ± 0.4) kJ -1) than Cu2O2 species 1c and 1c' (ΔH12° = -81 to -77 kJ mol-1, respectively), which are formed from mononuclear precursors. There is a substantially larger overall formation entropy for 2c [ΔS12° = (-89.3 ± 1.5) J K-1 mol-1 compared to -220 and -203 J K-1 mol-1 for 1c and 1c', respectively] since Cu2O2 formation is an intramolecular, rather than intermolecular, process. Examination of other kinetic parameters and spectral differences provides complementary information that 2c has a strained structure. In fact, 2c is not the ultimate oxidation product: relief of steric constraints occurs at higher temperatures by a slow rearrangement (λ(max) = 540 nm → λ(max) = 529 nm) producing {Cu2O2}(n) oligomers containing intermolecular Cu-O2-Cu bonds. A particularly stable trimer species [{(D1)Cu2(O2)}3]6+ (2d) was characterized, with ΔH3° = (-153 kJ mol-1)/3 = -51 kJ mol-1 per Cu2O2 unit, intermediate between that seen for 2c, 1c, and 1c'.
N2O decomposition over Fe-zeolites: Structure of the active sites and the origin of the distinct reactivity of Fe-ferrierite, Fe-ZSM-5, and Fe-beta. A combined periodic DFT and multispectral study
Sklenak, Stepan,Andrikopoulos, Prokopis C.,Boekfa, Bundet,Jansang, Bavornpon,Novakova, Jana,Benco, Lubomir,Bucko, Tomas,Hafner, Juergen,Ddeek, Jii,Sobalik, Zdenk
, p. 262 - 274 (2010)
The N2O decomposition over Fe-ferrierite, Fe-beta, and Fe-ZSM-5 has been recently studied [K. Jisa, J. Novakova, M. Schwarze, A. Vondrova, S. Sklenak, Z. Sobalik, J. Catal. 262 (2009) 27] and a superior activity of Fe-ferrierite with respect to Fe-beta and Fe-ZSM-5 has been shown. In this study, we investigated (1) plausible active sites for the N2O decomposition over Fe-ferrierite and (2) the origin of the distinct reactivity of Fe-ferrierite, Fe-ZSM-5 and Fe-beta employing a combined theoretical (periodic DFT) and experimental (UV-vis-NIR spectroscopy, IR spectroscopy, 29Si MAS NMR spectroscopy and catalytic batch experiments) approach. We evidenced that two Fe(II) cations accommodated in two adjacent six-membered rings in the eight-membered ring channel (β sites) of Fe-ferrierite (the calculated Fe-Fe distance is 7.4 ) form the active site responsible for the superior activity of this catalyst in the N2O decomposition in the absence of NO. Similar structures can be formed in Fe-beta. However, the probability of their formation is very low. For Fe-ZSM-5, the geometrical arrangement of the cationic positions is far from that in Fe-ferrierite and it is not suitable for the N2O decomposition. Therefore, the predicted order of the activity of the Fe(II) exchanged zeolites agrees with our experimental findings and it is: Fe-ferrierite ? Fe-beta > Fe-ZSM-5. We further showed that the accommodation of divalent cations in rings forming cationic sites can lead to significant rearrangements of the local structures of the zeolite framework, and therefore, the precise structure of sites binding a divalent cation cannot be derived from results of X-ray diffraction experiments, but can be inferred from theoretical calculations.
Adsorbed Oxygen Species Formed by the Decomposition of N2O on Li/MgO Catalysts
Nakamura, Masato,Yanagibashi, Hiroshi,Mitsuhashi, Hiroyuki,Takezawa, Nobutsune
, p. 2467 - 2472 (1993)
A considerable amount of adsorbed oxygen species were produced by the decomposition of N2O on Li/MgO.The amount of the oxygen species greatly increases by Li(I)-doping on MgO.Over 0.7 wtpercent Li/MgO, the amount of the oxygen species formed was 10.67 μmol m-2.The temperature-programmed desorption of the oxygen species revealed that two types of adsorbed oxygen species were present on Li/MgO; one (α-oxygen species) desorbed in proportion to the second order in the amount of the adsorbed species with an activation energy of 141 kJ mol-1, giving a peak (α-oxygen peak) at 673-693 K; the other (β-oxygen species) desorbed in proportion to the first order in the amount of the adsorbed species with an activation energy of 219 kJ mol-1, giving a peak (β-oxygen peak) at 753-768 K.A weak α-oxygen peak occurred on MgO and no β-oxygen peak was discerned.On Li/MgO, a β-oxygen peak appeared along with an α-oxygen peak.At higher Li-loadings the β-oxygen peak was more intense than the α-oxygen peak.The sites for these oxygen species were suggested to be derived by the addition of Li(I) on MgO.It was suggested that the α-oxygen species were present at the surface sites on higher index faces of MgO, whereas the β-oxygen species were present at oxygen vacancies in the vicinity of Li(I) substituting for Mg(II).The hydrolysis of these adsorbed oxygen species yielded an appreciable amount of H2O2, suggesting that these species were primarilly present as surface peroxide on MgO and Li/MgO.
A comparative XAS and X-ray diffraction study of new binuclear Mn(III) complexes with catalase activity. Indirect effect of the counteranion on magnetic properties
Fernandez, Gema,Corbella, Montserrat,Alfonso, Montserrat,Stoeckli-Evans, Helen,Castro, Isabel
, p. 6684 - 6698 (2004)
Four new binuclear Mn(III) complexes with carboxylate bridges have been synthesized: [{Mn(nn)(H2O)}2(μ-ClCH2-COO) 2(μ-O)](ClO4)2 with nn = bpy (1) or phen (2) and [{Mn(bpy)(H2O)}2(μ-RCOO)2(μ-O)] (NO3)2 with RCOO = ClCH2COO (3) or CH 3COO (4). The characterization by X-ray diffraction (1 and 3) and X-ray absorption spectroscopy (XAS) (1-4) displays the relevance of this spectroscopy to the elucidation of the structural environment of the manganese ions in this kind of compound. Magnetic susceptibility data show an antiferromagnetic coupling for all the compounds: J = -2.89 cm-1 (for 1), -8.16 cm-1 (for 2), -0.68 cm-1 (for 3), and -2.34 cm-1 (for 4). Compounds 1 and 3 have the same cation complex [{Mn(bpy)(H2O)}2(μ-ClCH2COO) 2(μ-O)]2+, but, while 1 shows an antiferromagnetic coupling, for 3 the magnetic interaction between Mn(III) ions is very weak. The four compounds show catalase activity, and when the reaction stopped, Mn(II) compounds with different nuclearity could be obtained: binuclear [{Mn(phen) 2}(μ-ClCH2COO)2](ClO4) 2, trinuclear [Mn3(bpy)2(μ-ClCH 2COO)6], or mononuclear complexes without carboxylate. Two Mn(II) compounds without carboxylate have been characterized by X-ray diffraction: [Mn(NO3)2(bpy)2][Mn(NO 3)(bpy)2(H2O)]NO3 (5) and [Mn(bpy)3](ClO4)2·0.5 C 6H4-1,2-(COOEt)2·O.5H2O (8).
Kinetics of N2O Decomposition on the Surface of γ-Al2O3 doped with Sodium Ions
Kordulis, Christos,Vordonis, Leonidas,Lycourghiotis, Alexis,Pomonis, Phillipos
, p. 627 - 634 (1987)
The kinetics of N2O decomposition on a series of specimens prepared by doping γ-Al2O3 with various amounts of Na+ ions has been studied at various temperatures using a flow-bed reactor working under atmospheric pressure.This doping promotes the adsorption of oxygen anions produced from surface decomposition, presumably via the formation of surface species +...O-...Na+>, bringing about a transformation of the rate equation from R=k into R=kbN2OPN2O/bO2P1/2O2 (where bN2O and bO2 are adsorption coefficients and PN2O and PO2 are partial pressures).Moreover, a decrease in catalytic activity, expressed either as fractional conversion or rate of reaction, was observed on increasing the surface coverage C, of γ-Al2O3 with Na+ ions determined by X-ray photoelectron spectroscopy.Specifically, the dependence of the catalytic activity on the surface coverage of γ-Al2O3 is described by the relationship 1n(1/R) = 15.4+(281/K)C (where K is a proportionality constant) and it was concluded that the deactivation observed is due to the promotion of the O2 adsorption caused by the Na+ ions.Finally, the linear dependence of the surface coverage of γ-Al2O3 on the sodium content strongly suggests that the dispersion of the sodium supported species is constant irrespective of the surface concentration of sodium.
Formation of the surface NO during N2O interaction at low temperature with iron-containing ZSM-5
Bulushev, Dmitri A.,Renken, Albert,Kiwi-Minsker, Lioubov
, p. 305 - 312 (2006)
Interaction of N2O at low temperatures (473-603 K) with Fe - ZSM-5 zeolites (Fe, 0.01-2.1 wt %) activated by steaming and/or thermal treatment in He at 1323 K was studied by the transient response method and temperature-programmed desorption (TPD). Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) of NO adsorbed at room temperature as a probe molecule indicated heterogeneity of surface Fe(II) sites. The most intensive bands were found at 1878 and 1891 cm-1, characteristic of two types mononitrosyl species assigned to Fe2+(NO) involved in bi- and oligonuclear species. Fast loading of atomic oxygen from N2O on the surface and slower formation of adsorbed NO species were observed. The initial rate of adsorbed NO formation was linearly dependent on the concentration of active Fe sites assigned to bi- and oligonuclear species, evolving oxygen in the TPD at around 630-670 K. The maximal coverage of a zeolite surface by NO was estimated from the TPD of .NO at ～700 K. This allowed the simulation of the dynamics of the adsorbed NO formation at 523 K, which was consistent with the experiments. The adsorbed NO facilitated the atomic oxygen recombination/desorption, the rate determining step during N2O decomposition to O2 and N2, taking place at temperatures ≥563 K.
