Die Umsetzung von Dialkylaluminiumchloriden mit Bis(trimethylsilyl)hydrazin: Bildung von Addukten R2AlCl · NH2NHSiMe3 mit dem thermisch unbeständigen Trimethylsilylhydrazin

The Reaction of Dialkylaluminium Chlorides with Bis(trimethylsilyl)hydrazine: Formation of the Adducts R₂AlCl · NH₂NHSiMe₃ Containing the Unstable Monotrimethylsilylhydrazine Bis(trimethylsilyl)hydrazine did not react with dialkylaluminium chlorides R₂AlCl [R = CH₂CMe₃, CMe₃ and CH(SiMe₃)₂] by the formation of trimethylchlorosilane, but by dismutation to yield tris(trimethylsilyl)hydrazine and trimethylsilylhydrazine. The unstable, sterically less shielded NH₂NHSiMe₃ was stabilized by the coordination to the coordinatively unsaturated aluminium compounds. The adducts R₂AlCl · NH₂NHSiMe₃ were formed, which were characterized by crystal structure determinations with R = CMe₃ and CH(SiMe₃)₂. In all cases, the hydrazine derivative binds to the aluminium atoms via the more basic NH₂ nitrogen atom. The adduct Me₃CAlCl₂ · NH₂N(SiMe₃)₂ containing intact 1,1‐bis(trimethylsilyl)hydrazine as a ligand was isolated in a trace amount and also characterized by a crystal structure determination.     

The thermal decomposition of ammonium heptamolybdate

The thermal decomposition of ammonium heptamolybdate has been investigated by TG. The decomposition is discussed, making use of additional information obtained from isothermal studies, X-ray and IR measurements. The formation of two new compounds, namely (NH₄)₂O · 14 MoO₃ and (NH₄)₂O · 22 MoO₃, prior to the formation of MoO₃ is detected, as well as the main intermediate compounds (NH₄)₂O · 2.5 MoO₃ or (NH₄)₂O · 3 MoO₃ (according to the water content of the starting material) and (NH₄)₂O · 4 MoO₃.     

First Characterization of an Extended Ammonium‐Ammonia Complex [{NH4(NH3)4}+(μ‐NH3)2] in the Crystal Structure of [NH4(NH3)4][Co(C2B9H11)2] · 2 NH3

The compound [NH₄(NH₃)₄][Co(C₂B₉H₁₁)₂] · 2 NH₃ ( 1 ) was prepared by the reaction of Na[Co(C₂B₉H₁₁)₂] with a proton‐charged ion‐exchange resin in liquid ammonia. The ammoniate 1 was characterized by low temperature single‐crystal X‐ray structure analysis. The anionic part of the structure consists of [Co(C₂B₉H₁₁)₂]^‐ complexes, which are connected via C‐H···H‐B dihydrogen bonds. Furthermore, 1 contains an infinite equation/tex2gif-stack-2.gif[{NH₄(NH₃)₄}⁺(μ‐NH₃)₂] cationic chain, which is formed by [NH₄(NH₃)₄]⁺ ions linked by two ammonia molecules. The N‐H···N hydrogen bonds range from 1.92 to 2.71Å (DHA = Donor···Acceptor angles: 136‐176°). Additional N‐H···H‐B dihydrogen bonds are observed (H···H: 2.3‐2.4Å).     

Kinetics and thermodynamics of thermal decomposition of NH<Subscript>4</Subscript>NiPO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O

The single phase NH₄NiPO₄·6H₂O was synthesized by solid-state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. XRD analysis showed that NH₄NiPO₄·6H₂O was a compound with orthorhombic structure. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involves the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. In the DTA curve, the two endothermic peaks and an exothermic peak, respectively, corresponding to the first two steps’ mass loss of NH₄NiPO₄·6H₂O and crystallization of Ni₂P₂O₇. Based on Flynn–Wall–Ozawa equation, and Kissinger equation, the average values of the activation energies associated with the thermal decomposition of NH₄NiPO₄·6H₂O, and crystallization of Ni₂P₂O₇ were determined to be 47.81, 90.18, and 640.09 kJ mol⁻¹, respectively. Dehydration of the five crystal water molecules of NH₄NiPO₄·6H₂O, and deamination, dehydration of the crystal water of NH₄NiPO₄·H₂O, intramolecular dehydration of the protonated phosphate group from NiHPO₄ together could be multi-step reaction mechanisms. Besides, the thermodynamic parameters (ΔH ^≠, ΔG ^≠, and ΔS ^≠) of the decomposition reaction of NH₄NiPO₄·6H₂O were determined.     

Novel Method for Preparing NH4NiPO4·6H2O: Hydrogen Bonding Coacervate Selective Self-assembly

The single phase NH₄NiPO₄·6H₂O was synthesized by solid‐state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. The NH₄NiPO₄·6H₂O and its calcined products were characterized using X‐ray powder diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform IR (FT‐IR), ultraviolet‐visible (UV‐vis) absorption spectroscopy, and scanning electron microscopy (SEM). The results showed that the product dried at 80°C for 3 h was orthorhombic NH₄NiPO₄·6H₂O [space group Pmm2(25)], and surfactant polyethylene glycol (PEG)‐400 can direct growth of crystal NH₄NiPO₄·6H₂O. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involve the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. The product of thermal decomposition at 150°C for 2 h, orthorhombic NH₄NiPO₄·H₂O, is layered compound with an interlayer distance of 0.8370 nm.     

Enzymatic Synthesis of Oligopeptide. Part II. Synthesis of Bis(N-Protected Amino Acid) Hydrazides by Papain

New hydrazide derivative identified as bis-di-N-acylamino acid hydrazide was synthesized from N-acylamino acid and hydrazine under papain catalysis. The reaction was carried out at pH 5.0, 38°C in a mixture containing 0.2M Z-X-OH⁺ or Boc-X-OH, 2% NH₂NH₂·H₂O, 0.8% β-mercaptoethanol, 0.1.% EDTA and 50 mg/ml of papain. The bis-hydrazide can be used in peptide synthesis via oxidation.     

Tetraammonium Diglycinyl‐octamolybdate(VI) Dihydrate, (NH4)4[(NH3CH2CO)2(Mo8O28)] · 2 H2O

The reaction of ammonium heptamolybdate with hydrazine sulfate in an aqueous solution of glycine at room temperature yielded colorless crystals of (NH₄)₄[(NH₃CH₂CO)₂(Mo₈O₂₈)] · 2 H₂O. The crystal is monoclinic, space group C2/c (no. 15), a = 17.234 Å, b = 10.6892 Å, c = 18.598 Å, β = 108.280°, V = 3253.2 ų, Z = 4. The crystal structure contains ammonium cations and isolated octamolybdate(4–) anions, [(NH₃CH₂CO)₂(Mo₈O₂₈)]^4–, with two zwitterionic glycine molecules as ligands.     

A candidate for an ion pair in the vapor phase: Proton transfer in complexes R3N - HX

Large-scale ab initio calculations have been performed on the complexes NH₃·HCl, NH₃·HBr, CH₃NH₂·HCl and CH₃NH₂·HBr. Two-dimensional energy surfaces as a function of R_N---X and R_HX have been scanned in order to explore the possibility for the formation of stable vapor-phase ion-pair complexes. While the complexes NH₃·HCl, NH₃·HBr and CH₃NH₂·HCl are still of the neutral type, the ionic form CH₃NH₃⁺·Br⁺ is energetically slightly more favourable than the neutral-type complex. Further increase in base strength of the amine will result in stable ionic amine HX complexes in the vapor phase.     

Study of SO2 Removal Using Non-thermal Plasma Induced by Dielectric Barrier Discharge (DBD)

Dielectric Barrier Discharge (DBD) non-thermal plasma reactors built with three different dielectric materials for SO₂ removal were studied. The discharge characteristics of the three dielectrics, namely glass, Teflon, and glass fiber-based epoxy resin, were analyzed using Lissajous figures. From the Lissajous figures, the transition charge and energy deposition for each dielectric material were determined. When both the discharge characteristics and mechanical processability were considered, glass fiber-based epoxy resin was regarded as the best dielectric barrier among the three for DBD plasma reactors. A multi-cell DBD reactor built with glass fiber-based epoxy resin was used for treating air stream containing SO₂. SO₂ % removal decreased with increasing initial SO₂ concentration in a biphasic fashion. SO₂ removal was greatly improved by adding NH₃ into the air stream. Raising the relative humidity of the air stream also helped SO₂ removal. A SEM (scanning electron microscope) test illustrated some changes in surface morphology of Teflon and glass fiber-based epoxy resin.     

(Me2NH2)[(Ph3Sn)3(MoO4)2], ein Triorganozinnmolybdat mit Schichtstruktur

(Me₂NH₂)[(Ph₃Sn)₃(MoO₄)₂], a Triorganotin Molybdate with Layer Structure The reaction of [(Ph₃Sn)₂MoO₄] with (Me₂NH₂)Cl in an acetonitrile/water mixture leads to the formation of (Me₂NH₂)[(Ph₃Sn)₃(MoO₄)₂] ( 1 ). ( 1 ) crystallizes in the space group Pca2₁ with a = 1967.0(4), b = 1353.1(2) and c = 2176.6(5) pm. In the crystal structure of 1 Ph₃SnO₂ bipyramides and MoO₄ tetrahedra are linked by corner sharing to give a layer structure. Additionally the layers are connected by O···H···N hydrogen bridges between MoO₄ groups and [Me₂NH₂]⁺ ions to give a 3D network structure.     

Hexamincyclotriphosphazenhemiammoniakat,P3N3(NH2)6 · 0,5 NH3, ein Produkt der Hochdruckammonolyse von weißem Phosphor

Hexaminecyclotriphosphazenehemiammoniate, P₃N₃(NH₂)₆ · 0.5 NH₃, a Product of High Pressure Ammonolysis of White Phosphorus White phosphorus gives at NH₃-pressures ≥5 kbar and temperatures above 250°C in a disproportionation reaction P₃N₃(NH₂)₆ · 0.5 NH₃; besides these products red phosphorus is formed. The yield on P₃N₃(NH₂)₆ · 0.5 NH₃ increases with T and is about 70–80% at 400°C as to the disproportionation reaction of the amount of white phosphorus. X-ray structure determination was successful on single crystals of P₃N₃(NH₂)₆ · 0.5 NH₃. Pbca, N = 8 a = 11.395(3) Å, b = 12.935(4) Å, c = 12.834(4) Å R = 0.035, R_w = 0.041 with w = 1, N (F_o²) ≥ 3σ(F_o²) = 1371, N(Var.) = 166. The molecules are connected by N? H? N-bridgebonds with 3.04 Å ≤ d(N …? N) ≤ 3,19 Å and d (N? H) = 0.87 Å. The compound is furthermore characterized by IR-data and its thermical behaviour.     

An insight into C?H···N hydrogen bond and stability of the complexes formed by trihalomethanes with ammonia and its monohalogenated derivatives

A theoretical study of the C? H···N hydrogen bond in the interactions of trihalomethanes CHX₃ (X = F, Cl, Br) with ammonia and its halogen derivatives NH₂Y (Y = F, Cl, Br) has been carried out thoroughly. The complexes are quite stable, and their stability increases in going from CHF₃ to CHCl₃ then to CHBr₃ when Y keeps unchanged. With the same CHX₃ proton donor, enhancement of the gas phase basicity of NH₂Y strengthens stability of the CHX₃···NH₂Y complex. The C? H···N hydrogen bond strength is directly proportional to the increase of proton affinity (PA) at N site of NH₂Y and the decrease of deprotonation enthalpy (DPE) of C? H bond in CHX₃. The CHF₃ primarily appears to favor blue shift while the red‐shift is referred to the CHBr₃. The blue‐ or red‐shift of CHCl₃ strongly depends on PA at N site of NH₂Y. We suggest the ratio of DPE/PA as a factor to predict which type of hydrogen bond is observed upon complexation. The SAPT2+ results show that all C? H···N interactions in the complexes are electrostatically driven regardless of the type of hydrogen bond, between 48% and 61% of the total attractive energy, and partly contributed by both induction and dispersion energies.     

Preparation and characterization of microencapsulated LDHs with melamine‐formaldehyde resin and its flame retardant application in epoxy resin

Layered double hydroxides (LDHs) are emerging as a new and green high‐efficient flame retardant. But LDHs aggregate seriously because of their hydrophilicity, which affect deeply the mechanical and flame retardant properties of their composites. For the first time in this paper, microencapsulated LDHs (MCLDHs) with melamine‐formaldehyde (MF) resin were prepared by microencapsulation technology to enhance their compatibility and dispersion within epoxy resin (EP). The mechanical and flame retardant performances of EP/MCLDH composite were studied by comparing with EP/LDH composite. Results showed that the water contact angle of MCLDHs increased from 8.9° to 122.1°, which indicated good compatibility. The particle size of MCLDHs decreased sharply, and more than one‐third were up to submicron scale, which can be conducive to dispersion. Moreover, the tensile strength and elongation at break of EP/MCLDHs with different flame retardant contents were higher than those of EP/LDHs. And the addition of MCLDHs increased the glass transition temperature (Tg) of EP/MCLDHs, which meant a strong interfacial interaction. Besides, compared with EP/LDHs, the limiting oxygen index values of EP/MCLDHs were higher, and its peak of heat release rate and total heat release decreased by 16.3% and 5.5% respectively. EP/MCLDHs achieved from V‐1 to V‐0 rate with the increasing content of MCLDHs from 20% to 30%, while LDHs/EP never passed tests. In the process of heating, H₂O, CO₂, and NH₃ released from MCLDHs formed gaseous phase, and the remaining dense char layers and oxides produced condensed phase, which played an important role in inhibiting combustion.     

An insight into CH···N hydrogen bond and stability of the complexes formed by trihalomethanes with ammonia and its monohalogenated derivatives

A theoretical study of the C?H···N hydrogen bond in the interactions of trihalomethanes CHX₃ (X = F, Cl, Br) with ammonia and its halogen derivatives NH₂Y (Y = F, Cl, Br) has been carried out thoroughly. The complexes are quite stable, and their stability increases in going from CHF₃ to CHCl₃ then to CHBr₃ when Y keeps unchanged. With the same CHX₃ proton donor, enhancement of the gas phase basicity of NH₂Y strengthens stability of the CHX₃···NH₂Y complex. The C?H···N hydrogen bond strength is directly proportional to the increase of proton affinity (PA) at N site of NH₂Y and the decrease of deprotonation enthalpy (DPE) of C?H bond in CHX₃. The CHF₃ primarily appears to favor blue shift while the red‐shift is referred to the CHBr₃. The blue‐ or red‐shift of CHCl₃ strongly depends on PA at N site of NH₂Y. We suggest the ratio of DPE/PA as a factor to predict which type of hydrogen bond is observed upon complexation. The SAPT2+ results show that all C?H···N interactions in the complexes are electrostatically driven regardless of the type of hydrogen bond, between 48% and 61% of the total attractive energy, and partly contributed by both induction and dispersion energies.     

大比表面积钛黑颜料的制备和表征

本文首次通过pH值控制沉淀法制备前驱物丁二酸钛肼复盐, 并进一步热分解制备大比表面积钛黑颜料-黑色钛氧化物。通过比表面积(BET)、电子能谱(EDS)、X射线光电子能谱分析(XPS)、X射线粉末衍射(XRD)、场发射扫描电子显微镜(HRSEM)、物理吸附仪、激光粒度仪和Color i5型台式分光测色仪对黑色钛氧化物进行了表征, 确定了黑色钛氧化物的组成为2TiO₂·Ti₂O₃, 其表面积为53.854 4 m²·g^-1。并考察了酸源、水合肼用量、酸钛比、反应时间、pH、NaOH浓度和煅烧温度等各种反应参数对黑色钛氧化物的颗粒尺寸、分布均匀性和黑色度的影响。用元素分析仪和等离子体光谱仪测定了前驱物组成, 确定其组成为[Ti(C₄H₄O₄)₂]_0.85·2Ti₂O₃·6N₂H₄·3H₂O, 并探讨了黑色钛氧化物形成机理, 为新型混合价材料黑色钛氧化物的制备提供重要参考依据。     

Synthesis of Ammonium‐ and 4‐Dimethylaminopyridinium Amidofluorophosphates and Crystal Structure of [DMAPH][PO2F(NH2)]

NH₄[PO₂F(NH₂)] has been prepared by the reaction of a betaine py·PO₂F with excess ammonia in acetonitrile solution, while the ammonolysis of DMAP·PO₂F with a stoichiometric amount of NH₃ yields [DMAPH][PO₂F(NH₂)]. The crystal structure of the latter was determined by single‐crystal X‐ray diffraction, which revealed that the anions [PO₂F(NH₂)]^— are linked to infinite chains by double N—H···O bridges. Additional strong N—H···O bridging bonds connect each anion with its [DMAPH]⁺ counterion. The formation of a new betaine NH₃·PO₂F in the solution of py·PO₂F in liquid ammonia was proved by ³¹P NMR spectroscopy and by identification of its hydrolysis products.     

Kinetics and mechanism of the reduction of monochloramine by hydroxylamine and hydroxylammonium ion

The kinetics and mechanism by which monochloramine is reduced by hydroxylamine in aqueous solution over the pH range of 5–8 are reported. The reaction proceeds via two different mechanisms depending upon whether the hydroxylamine is protonated or unprotonated. When the hydroxylamine is protonated, the reaction stoichiometry is 1:1. The reaction stoichiometry becomes 3:1 (hydroxylamine:monochloramine) when the hydroxylamine is unprotonated. The principle products under both conditions are Cl^–, NH⁺₄, and N₂O. The rate law is given by ?[d[NH₂Cl]/dt] = k₊[NH₃OH⁺][NH₂Cl] + k₀[NH₂OH][NH₂Cl]. At an ionic strength of 1.2 M, at 25°C, and under pseudo‐first‐order conditions, k₊= (1.03 ± 0.06) ×10³ L · mol^?1 · s^?1 and k₀=91 ± 15 L · mol^?1 · s^?1. Isotopic studies demonstrate that both nitrogen atoms in the N₂O come from the NH₂OH/NH₃OH⁺. Activation parameters for the reaction determined at pH 5.1 and 8.0 at an ionic strength of 1.2 M were found to be ΔH? = 36 ± 3 kJ · mol^–1 and Δ S? = ?66 ± 9 J · K^?1 · mol^?1, and Δ H? = 12 ± 2 kJ · mol^?1 and Δ S? = ?168 ± 6 J · K^?1 · mol^?1, respectively, and confirm that the transition states are significantly different for the two reaction pathways. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 124–135, 2006     

Non-isothermal kinetics of thermal decomposition of NH<Subscript>4</Subscript>ZrH(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>·H<Subscript>2</Subscript>O

Nanocrystalline NH₄ZrH(PO₄)₂·H₂O was synthesized by solid-state reaction at low heat using ZrOCl₂·8H₂O and (NH₄)₂HPO₄ as raw materials. X-ray powder diffraction analysis showed that NH₄ZrH(PO₄)₂·H₂O was a layered compound with an interlayer distance of 1.148 nm. The thermal decomposition of NH₄ZrH(PO₄)₂·H₂O experienced four steps, which involves the dehydration of the crystal water molecule, deamination, intramolecular dehydration of the protonated phosphate groups, and the formation of orthorhombic ZrP₂O₇. In the DTA curve, the three endothermic peaks and an exothermic peak, respectively, corresponding to the first three steps' mass losses of NH₄ZrH(PO₄)₂·H₂O and crystallization of ZrP₂O₇ were observed. Based on Flynn–Wall–Ozawa equation and Kissinger equation, the average values of the activation energies associated with the NH₄ZrH(PO₄)₂·H₂O thermal decomposition and crystallization of ZrP₂O₇ were determined to be 56.720 ± 13.1, 106.55 ± 6.28, 129.25 ± 4.32, and 521.90 kJ mol⁻¹, respectively. Dehydration of the crystal water of NH₄ZrH(PO₄)₂·H₂O could be due to multi-step reaction mechanisms: deamination of NH₄ZrH(PO₄)₂ and intramolecular dehydration of the protonated phosphate groups from Zr(HPO₄)₂ are simple reaction mechanisms.     

Solubility in the magnesium chlorate-carbamide-water system at 50°C

The solubility of phases in the magnesium chlorate-carbamide-water system was studied by the isothermal solubility method at 50°C. The crystallization branches of carbamide, magnesium chlorate hexahydrate, Mg(ClO₃)₂ · 6CO(NH₂)₂, Mg(ClO₃)₂ · 4CO(NH₂)₂ · 2H₂O, and Mg(ClO₃)₂ · 2CO(NH₂)₂ · 4H₂O were revealed in the phase diagram.     

Nieuwland's cuprocatalytic reaction in terms of crystal chemical analysis

Crystallochemical treatment of the Nieuwland reaction is carried out on the basis of structural data obtained for crystalline acetylene complexes of the formulas NH₄Cu₈Cl₉·4C₂H₂·1/2HCu₂Cl₃·H₂O (I), NH₄Cu₃Cl₄·C₂H₂ (II), KCu₈Cl₉·4C₂H₂·1/2HCu₂Cl₃·H₂O (III), KCu₃Cl₄·C₂H₂ (IV), (NH₄)₂Cu₃Cl₅·4/9H₂O·(xC₂H₂) with x=0 (Va), 1/9 (Vb), and 4/9 (Vc) and divinylacetylene (DVA) copper chloride compounds 2CuCl·DVA (VI) and 3CuCl·DVA (VII). Because of the π-coordination of a copper atom, the C≡C bond of the acetylene molecule is activated, as indicated by its significant (up to 1.32 Å) stretch (complexes I and II). The zeolite-like structure of complexes Va-Vc, which form in a catalytic solution, is realized as an infinite {[Cu₁₀₈Cl₁₆₈(H₂O)₁₆]^60?}_n anion with discrete [Cl(NH₄)₆]⁵⁺ cations inside. In this structure, only 16 Cu(1) atoms have a trigonal-pyramidal environment with the oxygen atom of the crystallization water located in the vertex (d_Cu?O=2.79 Å). Under the liquid-phase conditions of the Nieuwland reaction, these copper atoms are active centers stimulating the reaction to the subsequent acetylene oligomerization due to the π-interaction with the C₂H₂ molecule. The mutual arrangement of the catalytically active Cu(1) atoms in structure Va serves as a matrix for the synthesis of DVA, as shown by the structure of the 2CuCl·DVA adduct.