Die sechsgliedrigen Ringsysteme PIIISi2N2O, [PVSi2N2O]⊕ und PVSi2N2O

Compounds I-X of the sixmembered ring system PSi₂N₂O with phosphorus in different oxidation and bond numbers, collected in Schema 1, have been prepared for the first time and confirmed in their structure by elemental analysis as well as by infrared and¹H- and³¹P-spectroscopy.

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Mit Auszügen aus der DissertationK. P. Giesen, Techn. Univ. Braunschweig 1972.     

Neue anorganische Ringsysteme. XV. Die sechsgliedrigen Ringsysteme PIIISi2N3, [PvSi2N3]⊕ und PvSi2N3

Novel Inorganic Ring Systems. XV. The Sixmembered Ring Systems P^IIISi₂N₃, [P^VSi₂N₃]^⊕ and P^VSi₂N₃ Compounds I–X of the sixmembered ring system PSi₂N₃ with phosphorus in different oxidation and bond numbers, collected in scheme 1, have been prepared for the first time and confirmed in their structure by elemental analysis as well as by infrared and ¹H and ³¹P spectroscopy.     

Höhere,kondensierte Ringsysteme. 4. Mitteilung. Grosse Ringe der [2n]Metacyclophanreihe

[2⁷] Metacyclophane, [2⁹] metacyclophane, and [2¹⁰] metacyclophane with a 50-membered ring are isolated in the pure state from the crude product of a WURTZ reaction with m-xylylene dibromide, thus providing for the first time a complete series of cyclophanes with two to ten sub-units. The structure of the new ring systems is determined from their UV., IR., NMR. and mass spectra. The physical constants of these large carbocyclic systems are compared with those of the well-known smaller metacyclophanes, particularly with respect to conformation.     

Heterodyne measurements of hot bands and isotopic transitions of N2O near 7.8 µm

Heterodyne frequency measurements are reported for absorption transitions of N₂O in the frequency range from 1257 to 1335 cm^?1. The measurements use a CO laser as a transfer oscillator whose frequency is measured directly against combinations of frequencies of two stabilized CO₂ lasers whose frequencies are well known. A tunable diode laser is locked to the N₂O absorption feature and the frequency difference is measured between the diode laser and the CO laser. Thev ₃ fundamental bands of the¹⁵N¹⁴N¹⁶O and¹⁴N¹⁵N¹⁶O isotopes are reported. Measurements are also given for the 00⁰2–00⁰1, 02⁰1–02⁰0, and 02²1–02²0 vibrational transitions of N₂O. A table of frequencies is given for the 00⁰2–00⁰0 band near 2560 cm^?1 based on these and earlier measurements.     

Synthese und Molekülstruktur neuer Ringsysteme aus 1,1,3,3-Tetrachlor-1,3-diphosphapropan

Synthesis and Molecular Structure of new Ring Systems from 1,1,3,3-Tetrachloro-1,3-diphosphapropane 1,1,3,3-Tetrachloro-1,3-diphosphapropane 1 reacts in two different ways to form new heterocycles. Partial oxidation of 1 with tetrachloroorthobenzoquinone furnishes the methylene-bridged λ³P, λ⁵P species 3 . Subsequent reactions with di- and triethylamine lead to the condensed ring system 6 with the P?C bonds connected to a central four-membered ring. Compound 6 displays crystallographic inversion symmetry, a short transannular P? P distance and an extremely distorted tetrahedral coordination geometry at the four-membered ring phosphorus atoms. 1 reacts with 7 to give the heterocycle 8 with a central eight-membered ring involving four phosphorus atoms. The eight – membered ring shows a ?bent”? crown conformation, the condensed five – membered rings display envelope conformation.     

Synthesis and 15N- and 17O-NMR Spectra of 5-Methyl(15N2)[O2,O4-17O2]uridine (= (15N2)[O2,O4-17O2]Ribosylthymine)

The 5-methyl(¹⁵N₂)[O²,O⁴-¹⁷O₂]uridine (= (¹⁵N₂)[O²,O⁴-¹⁷O ₂]ribosylthymine; 15 ) was synthesized and analyzed by ¹⁵N- and ¹⁷O-NMR spectroscopy. (¹⁵N₂)Urea was condensed with 2,3-dibromo-2-methylpropanoyl chloride ( 3 ) and cyclized to form (¹⁵N₂)thymine ( 5 ). After glycosidation, the ¹⁷O isotopes were introduced in two separate steps: hydrolytic ring opening of 2,5′-anhydro derivative 9 and hydrolysis of 3-nitro-1H-1,2,4-triazole derivative 12 with labelled water in the presence of a strong base. The ¹⁵N- and ¹⁷O-NMR spectra (Fig.) of 15 in phosphate-buffered water serve as references for heteronuclear NMR spectra of labelled RNA fragments.     

The Synthesis of Some New Sulfur-Bearing Various Heterocyclic Systems Derived from Asymmetrical N,N′-Disubstituted Thiourea Derivatives

The heterocyclization of an asymmetrical N,N′-disubstituted thiourea (1a–d) in ring closure reactions with Br₂/AcOH, ethyl chloroacetate, diethyl oxalate, diethyl malonate, and hydrazine hydrate led to the direct formation of sulfur-bearing various heterocyclic systems (2–8) in which the thiaenolization is toward the aryl group. The synthetic work and reactivity investigations have been well supported by standard modern spectroscopic techniques (IR, ¹ H NMR, ¹³ C NMR, mass spectrum, and microanalysis).     

Nitrosonium Nitrate,an Isomer of N2O4 in IF5

N₂O₄ dissolves in IF₅ as NO⁺NO₃^–, as established by n.m.r spectroscopy, and in the solid state the solvate complex NO⁺NO₃^– · IF₅ is formed. This contains a double chain of alternating NO⁺ cations and NO₃^– anions. (a = 483.4(2), b = 773.9(1), c = 932.6(3) pm, (α = 70.18(2)°, β = 80.90(3)°, (γ = 87.34(2)°, space group P1, Z = 2).     

Crystal structure of 2-aminopyridine-5-sulfonic acid and its 2D coordination polymer [Ag(C5H5N2O3S)] n

The crystal structure of an organosulfonate ligand 2-aminopyridine-5-sulfonic acid is reported here. Reaction of AgNO₃ and the 2-aminopyridine-5-sulfonic acid in basic ethanol/aqueous solution gave [Ag(C₅H₅N₂O₃S)] _n (1). X-ray crystallographic study reveals that 1 is a 2D network structure constructed by strong Ag-pyridine, Ag–NH₂ interactions and weaker Ag-sulfonate interactions. The replacement of the benzene ring by the pyridine ring causes the coordination modes of the sulfonate group to change from μ ³ to μ². Its TG/DSC property is also discussed.     

Synthese,Kristallstruktur und Eigenschaften eines neuen Sialons – SrSiAl2O3N2

Synthesis, Crystal Structure, and Properties of a New Sialon – SrSiAl₂O₃N₂ The sialon SrSiAl₂O₃N₂ was obtained as a coarsly crystalline solid by reaction of silicon diimide, aluminum nitride, and strontium carbonate under N₂ atmosphere in a high-frequency furnace at 1650 °C. According to the single-crystal structure determination the title compound is isotypic with LnSi₃N₅ (Ln = La, Ce, Nd, Pr). SrSiAl₂O₃N₂ (P2₁2₁2₁, a = 491.98(6), b = 789.73(7), c = 1134.94(18) pm, Z = 4, R1 = 0.0439, wR2 = 0.0939). In the solid a three-dimensional network structure of corner sharing SiON₃, AlO₃N, and AlO₂N₂ tetrahedra occurs. Lattice energetic calculations using the MAPLE concept confirm an unequivocally correct crystallographic differentiation between N and O as well as Al and Si atoms, respectively (Al–O: 167.4(5)–170.6(6); Al–N: 175.4(6)–179.4(6); Si–O: 171.2(6); SiN: 176.7(6)–179.6(6) pm). The Sr²⁺ ions are located in the voids of the (SiAl₂O₃N₂)^2– framework (Sr–O: 250.4(6)–304.2(6); Sr–N: 287.4(6) 318.2(6) pm).     

Neue anorganische Ringsysteme. 34. Derivate eines Cyclo-1-thiaIV- und eines Cyclo-1-thiaIV- 3,4-disila-2,5-diazans

Novel Inorganic Ring Systems. 34. Derivatives of the Cyclo-1-thia^IV- and of the Cyclo-1-thia ^VI-3,4-disila-2,5-diazane Variations of fivemembered “hetero” cyclosilazanes of the type Si₂N₂El could be enlarged to the systems with El = SO and SO₂. They are obtained by the formation principles 4 + 1 and 2 + 3 respectively, according to the equation (1), (4) and (5). The prepared compound are described in their properties and confirmed in their structure (Tables 1–2).     

NMR study of O and N,O‐substituted 8‐quinolinol derivatives

The ¹H and ¹³C NMR spectral study of several biologically active derivatives of 8‐quinolinol have been made through extensive NMR studies including homodecoupling and 2D‐NMR experiments such as COSY‐45°, NOESY, and HeteroCOSY. Electron donating resonance and electron withdrawing inductive effect of several groups showed marked changes in chemical shifts of nuclei at the seventh positions of O‐substituted quinolinols (2–15). Although in N‐alkyl, 8‐alkoxyquinolinium halides (16–21), ring A rightly showed low frequency chemical shift values. Copyright © 2013 John Wiley & Sons, Ltd.     

The crystal structure of bisphenoxatelluronium dinitrate,C24H16O9N2Te2

Bisphenoxatelluronium dinitrate is monoelinie, P2₁/c: a = 11.638(4), b = 28.266(8), c = 8.546(3) å, β = 119.73(2)°, z = 4 at t = 22°. All atoms including hydrogen were located. The two ring systems, I and II, are folded along their Te-O axes, 147° and 163°, respectively. The average ring bond distances are: Te-C = 2.091, C-C = 1.377, C-O = 1.370 Å. Each Te is bonded to one NO₃ group, Te1-ON1 = 2.485(5), Te2-ON4 = 2.393(4) Å, and an oxygen bridge connects the ring systems, Te1-OB = 1.966(4), Te2-OB = 2.001(4) Å, Te1-OB-Te2 = 125.0(2)°. The bond distances and angles of the structure are compared to those of related compounds.     

Cavity ring‐down study of BrO radicals: Kinetics of the Br + O3 reaction and rate of relaxation of vibrationally excited BrO by collisions with N2 and O2

Cavity ring‐down (CRD) techniques were used to study the kinetics of the reaction of Br atoms with ozone in 1–205 Torr of either N₂ or O₂, diluent at 298 K. By monitoring the rate of formation of BrO radicals, a value of k(Br + O₃) = (1.2 ± 0.1) × 10⁻¹² cm³ molecule⁻¹ s⁻¹ was established that was independent of the nature and pressure of diluent gas. The rate of relaxation of vibrationally excited BrO radicals by collisions with N₂ and O₂ was measured; k(BrO(v) + O₂ → BrO(v − 1) + O₂) = (5.7 ± 0.3) × 10⁻¹³ and k(BrO(v) + N₂ → BrO(v − 1) + N₂) = (1.5 ± 0.2) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹. The increased efficiency of O₂ compared with N₂ as a relaxing agent for vibrationally excited BrO radicals is ascribed to the formation of a transient BrO–O₂ complex. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 125–130, 2000     

Competitive Coordination of the Uranyl ion by Perchlorate and Water – The Crystal Structures of UO2(ClO4)2·3H2O and UO2(ClO4)2·5H2O and a Redetermination of UO2(ClO4)2·7H2O (Z. Anorg. Allg. Chem. 2003, 629, 1012–1016)

In the article “Competitive Coordination of the Uranyl ion by Perchlorate and Water – The Crystal Structures of UO₂(ClO₄)₂·3H₂O and UO₂(ClO₄)₂·5H₂O and a Redetermination of UO₂(ClO₄)₂·7H₂O” (Z. Anorg. Allg. Chem. 2003 , 629, 1012–1016), some wrong parameters and bond lengths for UO₂(ClO₄)₂·7H₂O were given in table 1 and table 3 The correct parameters are: a = 1449.5(2) pm, b = 921.6(1) pm, c = 1067.5(2) pm, V = 1422.5(4)·10⁶ pm³, ρ = 2.712 g·cm^?3, μ = 119 cm^?1. The corrected bond lengths for this structure are U–O(1) 175.8(5) pm, U–O(2) 239.1(5) pm, U–O(3) 240.8(5), U–O(4) 242.0(7). A cif file with the correct data has been deposited with the ICSD.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

Regeneration characteristics and kinetics of Fe2O3/lignite semi-coke hot gas desulfurizer at O2/N2 atmosphere

The Fe₂O₃/lignite semi-coke sorbent was prepared by co-precipitation method with assistance of ultrasonic irradiation and underwent 4 sulfidation–regeneration cycles with O₂/N₂ as regeneration gases. The fresh, sulfided, and regenerated sorbents were characterized using XRD, SEM, XPS, and BET technologies in this paper. The regeneration mechanism was also discussed. It was found that in the oxygen atmosphere, FeS in the sulfided sorbent reacted with oxygen to produce Fe₂O₃ and SO₂, the sulfate formed in regeneration process is easy to decompose at higher temperature. Regeneration kinetic studies were also performed at regeneration temperatures of 625–700 °C. It was found that the reaction order of regeneration with respect to O₂ is first order. The equivalent grain model can be effectively used to correlate with the experimental data. In the early stage of reaction (x < 65 %), the regeneration is controlled by the chemical reaction, while it is controlled by the diffusion through the product layer in the latter stage (x > 70 %). According to the model, the apparent activation energy and the corresponding frequency factor for two different stages are 14.73 kJ mol^?1 and 4.43 × 10^?2 m s^?1, 31.32 kJ mol^?1 and 5.77 × 10^?4 m² s^?1, respectively.     

Hemoglobin as a nitrite anhydrase: modeling methemoglobin-mediated N2O3 formation

Nitrite has recently been recognized as a storage form of NO in blood and as playing a key role in hypoxic vasodilation. The nitrite ion is readily reduced to NO by hemoglobin in red blood cells, which, as it happens, also presents a conundrum. Given NO’s enormous affinity for ferrous heme, a key question concerns how it escapes capture by hemoglobin as it diffuses out of the red cells and to the endothelium, where vasodilation takes place. Dinitrogen trioxide (N₂O₃) has been proposed as a vehicle that transports NO to the endothelium, where it dissociates to NO and NO₂. Although N₂O₃ formation might be readily explained by the reaction Hb‐Fe³⁺+NO₂^?+NO?Hb‐Fe²⁺+N₂O₃, the exact manner in which methemoglobin (Hb‐Fe³⁺), nitrite and NO interact with one another is unclear. Both an “Hb‐Fe³⁺‐NO₂^?+NO” pathway and an “Hb‐Fe³⁺‐NO+NO₂^?” pathway have been proposed. Neither pathway has been established experimentally. Nor has there been any attempt until now to theoretically model N₂O₃ formation, the so‐called nitrite anhydrase reaction. Both pathways have been examined here in a detailed density functional theory (DFT, B3LYP/TZP) study and both have been found to be feasible based on energetics criteria. Modeling the “Hb‐Fe³⁺‐NO₂^?+NO” pathway proved complex. Not only are multiple linkage‐isomeric (N‐ and O‐coordinated) structures conceivable for methemoglobin–nitrite, multiple isomeric forms are also possible for N₂O₃ (the lowest‐energy state has an N? N‐bonded nitronitrosyl structure, O₂N? NO). We considered multiple spin states of methemoglobin–nitrite as well as ferromagnetic and antiferromagnetic coupling of the Fe³⁺ and NO spins. Together, the isomerism and spin variables result in a diabolically complex combinatorial space of reaction pathways. Fortunately, transition states could be successfully calculated for the vast majority of these reaction channels, both M_S=0 and M_S=1. For a six‐coordinate Fe³⁺‐O‐nitrito starting geometry, which is plausible for methemoglobin–nitrite, we found that N₂O₃ formation entails barriers of about 17–20 kcal mol^?1, which is reasonable for a physiologically relevant reaction. For the “Hb‐Fe³⁺‐NO+NO₂^?” pathway, which was also found to be energetically reasonable, our calculations indicate a two‐step mechanism. The first step involves transfer of an electron from NO₂^? to the Fe³⁺–heme–NO center ({FeNO}⁶) , resulting in formation of nitrogen dioxide and an Fe²⁺–heme–NO center ({FeNO}⁷). Subsequent formation of N₂O₃ entails a barrier of only 8.1 kcal mol^?1. From an energetics point of view, the nitrite anhydrase reaction thus is a reasonable proposition. Although it is tempting to interpret our results as favoring the “{FeNO}⁶+NO₂^?” pathway over the “Fe³⁺‐nitrite+NO” pathway, both pathways should be considered energetically reasonable for a biological reaction and it seems inadvisable to favor a unique reaction channel based solely on quantum chemical modeling.     

Guided ion beam studies of the reactions of O+, O 2 + , N+ and N 2 + with silane

Guided ion beam mass spectrometry is used to measure the cross sections as a function of kinetic energy for reaction of SiH₄ with O⁺(⁴S), O ₂ ⁺ (²Π_g,v=0), N⁺(³P), and N ₂ ⁺ (²Σ _g ⁺ ,v=0). All four ions react with silane by dissociative charge-transfer to form SiH _m ⁺ (m=0?3), and all but N ₂ ⁺ also form SiXH _m ⁺ products where (m=0?3) andX=O, O₂ or N. The overall reactivity of the O⁺, O ₂ ⁺ , and N⁺ systems show little dependence on kinetic energy, but for the case of N ₂ ⁺ , the reaction probability and product distribution relies heavily on the kinetic energy of the system. The present results are compared with those previously reported for reactions of the rare gas ions with silane [13] and are discussed in terms of vertical ionization from the 1t ₂ and 3a ₁ bands of SiH₄. Thermal reaction rates are also provided and dicussed.     

A “Mitsubishi emblem” tetrauclear aluminum complex containing two unsymmetric N2O2‐ligands and a symmetric NO3‐ligand as initiator for polymerization of rac‐lactide

A novel hydroxy‐, methoxy‐, and phenoxy‐bridge “Mitsubishi emblem” tetranuclear aluminum complex ( 1 ) is synthesized from an unsymmetric amine‐pyridine‐bis(phenol) N₂O₂‐ligand (H₂L¹) and a symmetric amine‐tris(phenol) NO₃‐ligand (H₂L²). Two same configuration chiral nitrogen atoms are formed in the tetranuclear Al complex upon coordination of the unsymmetric tertiary amine ligand to central Al. Complex 1 initiates controlled ring‐opening polymerization (ROP) of rac‐lactide and afford polylactide (PLA) with narrow molecular weight distributions (M_w/M_n = 1.05–1.19). The analysis of ¹H NMR spectra of the oligomer indicates that the methoxy group is the initiating group and the ring‐opening polymerization of lactide follows a coordination‐insertion mechanism. The Homonuclear decoupled ¹H NMR spectroscopy suggests the isotactic‐rich chains is preferentially formed in PLA. The study on kinetics of the ROP of lactide reveals the homopropagation rate is higher than the cross‐propagation rate, which is in agreement with the observed isotactic selectivity in the ROP of rac‐lactide. The stereochemistry of the polymerization was also supported by activation parameters. The introduction of unsymmetric ligand H₂L¹ has an effect on stereoslectivity of polymerization. This result may be of interest for the design of multinuclear metal complex catalysts containing functionalized ligands. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2084–2091