A direct approach to β-keto sulfones via AgNO3/K2S2O8 catalyzed aerobic oxysulfonylation of alkenes in aqueous medium

An efficient, AgNO₃/K₂S₂O₈ catalyzed one-pot radical route to β-keto sulfones from alkenes is reported. The protocol involves oxysulfonylation of alkenes with air (O₂) and inexpensive sodium arenesulfinate salts under mild conditions. It is highly practical and allows the use of easily available starting materials in an open flask and aqueous medium at ambient temperature.     

火焰辅助热解方法制备Ag_2O/TiO_2及其光催化制氢性能

以钛酸丁酯和硝酸银为前驱体,采用一步火焰辅助热解法制备了Ag_2O/TiO_2光催化剂并研究了样品在紫外-可见光照射下的光催化制氢性能。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见漫反射吸收光谱(UV-Vis DRS)对样品进行了表征。XRD结果表明TiO_2均为锐钛矿晶型,Ag的引入对XRD结果无明显影响。SEM图显示未修饰的TiO_2是微球形貌,随着引入Ag含量的增加,微球减少直至消失。通过XPS分析和化学沉淀法表明样品中Ag的存在形式为Ag_2O。UV-Vis DRS测试发现引入Ag后提高了样品的光吸收。前驱体中Ag的量影响样品的光催化活性,最高的光催化制氢的活性可以达到相同条件下的P25的15倍。对光催化反应后的样品进行分析,认为在光催化过程中部分Ag_2O通过光生电子转化为Ag形成Ag/TiO_2,进一步提高光催化制氢活性。     

火焰辅助热解方法制备Ag2O/TiO2及其光催化制氢性能

以钛酸丁酯和硝酸银为前驱体,采用一步火焰辅助热解法制备了Ag₂O/TiO₂光催化剂并研究了样品在紫外-可见光照射下的光催化制氢性能。利用X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）和紫外-可见漫反射吸收光谱（UV-Vis DRS）对样品进行了表征。XRD结果表明TiO₂均为锐钛矿晶型,Ag的引入对XRD结果无明显影响。SEM图显示未修饰的TiO₂是微球形貌,随着引入Ag含量的增加,微球减少直至消失。通过XPS分析和化学沉淀法表明样品中Ag的存在形式为Ag₂O。UV-Vis DRS测试发现引入Ag后提高了样品的光吸收。前驱体中Ag的量影响样品的光催化活性,最高的光催化制氢的活性可以达到相同条件下的P25的15倍。对光催化反应后的样品进行分析,认为在光催化过程中部分Ag₂O通过光生电子转化为Ag形成Ag/TiO₂,进一步提高光催化制氢活性。     

Thermal preparation and stabilization of crystalline silver particles in SiO<Subscript>2</Subscript>-based coating solutions

Ag/SiO₂ coating solutions for antimicrobial functionalisation can be prepared by a thermal reaction (reflux or solvothermal conditions) of mixtures of tetraethoxysilane, alkylamine compounds and AgNO₃. These coating solutions are especially useful for antimicrobial refinement of temperature sensitive materials like textiles or wood. Moreover coating application onto substrates such as glass or metal, as well as preparation of micrometer sized bulk particles by using a spray-drying process is also feasible. The efficiencies of AgNO₃ reduction in the presence of different amine compounds like triethanolamine, triethylamine or diethanolamine are compared. SiO₂ nanoparticles are formed by basic hydrolysis of tetraethoxysilane and stabilize the crystalline silver particles in the solution. The antimicrobial effect of silver containing coatings on textile fabrics is investigated.     

Silver nitrate-catalyzed oxidation of aldehydes to carboxylic acids by H2O2

A variety of aromatic, aliphatic and conjugated aldehydes were converted to the corresponding carboxylic acid derivatives with 30% H₂O₂ as the oxidant in the presence of catalytic amounts of AgNO₃. The method described has wide range of applicabilities, does not involve cumbersome work-up, exhibits chemoselectivity and proceeds under mild reaction conditions, and the resulting products are obtained in good yields within reasonable time.     

Synthesis and characterization of a new cyclic phosph(V)azane ligand [(C6H5N)P(O)H]2 and its zinc(II) complex

The new cyclic phosph(V)azane ligand [(C₆H₅N)P(O)H]₂ (2) is obtained from the reaction between PCl₃ and PhNH₂ in toluene followed by controlled hydrolysis of the product in an H₂O–CHCl₃ solution. Compound 2 is the first example of P(V) dimer [(µ-NC₆H₅)P(H)=O]₂, a P₂N₂ ring with two P(O)H moieties. The reaction of 2 with ZnCl₂ in a molar ratio of 1?:?1 in tetrahydrofuran yields the cyclophosph(V)azane complex Cl₂Zn[(C₆H₅N)P(O)H]₂ (3) in which Zn–O bonds form directly between a cyclic phosph(V)azane ligand and Zn(II). The products have been characterized by infrared, multinuclear (¹H, ³¹P, ¹³C) NMR, mass spectrometry, and elemental analysis.     

Trimethylsilylation of Alcohols and Phenols,and Direct Acetylation of Silyl Ethers Catalyzed by Fe(ClO4)3.6H2O

In this article, a mild and efficient protocol for the trimethylsilylation of various aliphatic and benzylic alcohols and phenols with trimethylsilyl chloride using a catalytic amount of ferric perchlorate at room temperature and relatively short reaction times in good to excellent yields is reported. Direct acetylation of trimethylsilyl ethers catalyzed with Fe(ClO ₄ ) ₃ .6H ₂ O(0.02 mmol)/Fe(ClO ₄ ) ₃ SiO ₂ (0.2 g) using acetic anhydride at ambient temperature is also reported.     

On the reduction of Cr3+ during the thermal decomposition of fluorochromates(III) with nitrogen containing cations

The thermal decomposition of [CO(NH₂)₂H]CrF₆·H₂O, (C₃N₆H₈)CrF₅·H₂O and the solid state reaction of CrF₃ and melamine are investigated under non-reciprocal quasi-static conditions and compared with the thermal behaviour of other fluorochromates(III) ([Cr(NH₃)₆]CrF₆, (NH₄)₃CrF and [C(NH₂)₃]₃CrF₆). The comparison of the results shows that the amount of chromium(II) in the final product is determined by the thermal stability and consequently by the decomposition temperature of the intermediates. Neither bonding properties in the starting materials nor the absolute amount of generated NH₃ influence the composition of the final product.     

Direct transformation of AgNO3 complex encapsulated Fullerene (C60) microcrystal on solid silver Nitrate Crystal without organic Ligands

We observed the unusual crystal transformation from solid AgNO₃ to Ag(I)-encapsulated fullerene (C₆₀) microcrystal by a coordination-driven crystallization, when casting C₆₀ solution on AgNO₃ crystal. The strong binding of Ag⁺-C₆₀ ruptures electrostatic interactions within AgNO₃ lattice, forming a binary hybrid material, which was characterized by XRD, Raman spectroscopy and mass spectrometry. Our results support the fact that AgNO₃ crystal can directly interact with fullerene C₆₀ molecules, other than through solvated metal cations. Two major factors, namely sturdy Ag⁺-olefin interaction and an enclosed cage effect play the dominating roles in crystal transformation. Adding to the regular solution-based crystallization, this facial protocol is expected to render an additional dimension in fabrication of exohedral metallofullerene architecture, regardless of solubility of metal cation in anti-solvent.     

An expedient synthesis of pyrrole-2-phosphonates via direct oxidative phosphorylation and γ-hydroxy-γ-butyrolactams from pyrroles

An expedient oxidative phosphorylation of pyrroles has been disclosed. The reaction of dialkyl phosphite and pyrrole in the presence of AgNO₃/K₂S₂O₈ in DMF/H₂O (8:1) produced pyrrole-2-phosphonates in good yields. In the absence of dialkyl phosphite, γ-hydroxy-γ-butyrolactam derivative was formed as a major product.     

Cu2O(SO4), dolerophanite: Refinement of the crystal structure,with a comparison of [O Cu(II)4] tetrahedra in inorganic compounds

The refinement of the crystal structure of Cu₂O(SO₄), dolerophanite, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; space group C 2/m;Z=4;R=0.035] confirmed the trigonal dipyramidal coordination of one Cu(II) atom (mean distance Cu-O=2.025 Å). One O atom is tetrahedrally surrounded by four Cu(II) atoms; the mean Cu(II)-O distance of 1.918 Å compares well to [O Cu(II)₄] tetrahedra found in inorganic crystal structures.de|Die Verfeinerung der Kristallstruktur von Cu₂O(SO₄), Dolerophanit, [a=9.370 (1) Å,b=6.319 (1) Å,c=7.639 (1) Å, =122.34 (1)°; Raumgruppe C 2/m;Z=4;R=0.035] bestätigte die trigonal dipyramidale Koordination des einen Cu(II)-Atoms (mittlerer Cu-O-Abstand=2.025 Å). Ein O-Atom ist tetraedrisch von vier Cu(II)-Atomen umgeben; der mittlere Cu(II)-O-Abstand von 1.918 Å entspricht den in ähnlichen [O Cu(II)₄]-Tetraedern von anorganischen Kristallstrukturen gefundenen Werten.

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Cu₂O(SO₄), Dolerophanit: Verfeinerung der Kristallstruktur mit einem Vergleich von [O Cu(II)₄]-Tetraedern in anorganischen Verbindungen

     

反式2-甲基-2-丁烯酸甲酯与臭氧反应机理的计算研究

采用G3B3方法构建反式2-甲基-2-丁烯酸甲酯与O3反应体系以及后续Criegee自由基有、无水分子参与下异构化反应的势能面剖面.结果表明,反式2-甲基-2-丁烯酸甲酯与O3反应首先生成一个稳定的五元环中间体,此中间体按断键位置不同后续裂解反应存在两条路径,分别生成产物P1(CH3CHOO+CH3OC(O)C(CH3)O)和P2(CH3CHO+CH3OC(O)C(CH3)OO).利用经典过渡态理论(TST)并结合Wigner矫正模型计算了200-1200 K温度区间内标题反应的速率常数kTST/W.计算结果显示,294 K时,该反应速率常数为7.55×10-18cm3molecule-1s-1,与Bernard等对类似反应所测实验值非常接近.生成的Criegee自由基(CH3CHOO和CH3OC(O)C(CH3)OO)可分别与水分子发生α-加成及β-氢迁移反应,其中Criegee自由基与水的α-加成反应较其与水的β-氢迁移反应具有优势.另外与无水分子参与CH3CHOO和CH3OC(O)C(CH3)OO异构化反应相比,水分子的参与使得异构化反应较为容易进行.     

Zur Kenntnis der wasserhaltigen schichtförmigen Alkali- und Erdalkali-Thiochromite der FormelM x (H2O) y CrS2

Two different polytypic series (2s and 3s) of layered alkali and alkaline earth thiochromites of formulaM _x(H₂O) _y CrS₂ (x=0.2–0.4;y=0.18–0.5) were prepared by topotactic ion exchange in 2H- and 3R- K _x (H₂O) _y CrS₂. The products were studied by TGA and X-ray diffraction techniques. Hydrates with monomolecular (hydrates I) and bimolecular (hydrates II) water layers between the CrS₂ slabs were observed. In the 3s series the CrS₂ layers are stacked according to 3R (Ib) (hydrates I) and 3R (Ia) (hydrates II) structures. In the 2s series the layer stacking leads to a 2H (Ib) structure and to a new orthorhombic 2 O structure.

Herrn Prof. Dr.K. Komarek zu seinem 60. Geburtstag gewidmet.     

Effect of process parameters on the concentration,current efficiency and energy consumption of electro-generated silver(II)

Electro-membrane generation of Ag(II) in nitric acid was experimentally explored in a three-electrode laboratory cell with respect to various operating parameters. DSA-O₂, titanium plate and saturated Ag/AgCl were employed as the anode, cathode and reference electrode, respectively. The considered process parameters included anolyte temperature and Ag(I) initial concentration, electrolysis time, current density and supporting electrolyte concentration. Parameter effect on the Ag(II) concentration, current density and energy consumption were determined by the Taguchi and ANOVA methods for test design and data analysis, respectively. The results revealed that current density, AgNO₃ concentration and temperature had noticeable effect on the generation of Ag(II). On the other hand, AgNO₃ concentration and current density showed the most dominant effect on the Ag(II) current efficiency: 48.5% and 30.3%, respectively. AgNO₃ concentration and current density were also found to have the highest effect on the energy consumption: 72.4% and 15.9%, respectively. Validity of the Taguchi method was also assessed by collecting the actual data.     

Two-dimensional supramolecular assembly of phenylmercury(II) and cadmium(II) complexes with a tridentate thiohydrazone NNS donor ligand: Synthesis,coordination behavior and crystal structure

The reaction of phenylmercury(II) acetate and cadmium(II) acetate with a refluxed solution of diacetylmonoxime and morpholine N-thiohydrazide formed a novel phenylmercury(II) complex, [PhHg(Hdammthiol)] (1) and a cadmium(II) complex, [Cd(Hdammthiol)₂] (2), respectively (where H₂dammthiol is the thiol form of diacetylmonoximemorpholine N-thiohydrazone (Hdammth) formed by the condensation of diacetylmonoxime and morpholine N-thiohydrazide in the presence of phenylmercury(II) and cadmium(II) ions). The complexes were characterised by elemental analyses and spectral data (electronic, infrared and ¹H NMR) and also by X-ray crystal structure analysis. The X-ray crystallography shows that the phenylmercury(II) complex attained a tricoordinated distorted T-shaped structure, while the cadmium(II) complex attained a trapezoidal bipyramidal geometry. The phenylmercury(II) complex forms a two-dimensional sheet via C–H?O and O–H?N hydrogen bonding and also forms a two-dimensional supramolecular dimer, having C–H?π synthons. Intermolecular C–H?O and O–H?O hydrogen bonding of the cadmium(II) complex forms a two-dimensional supramolecular sheet along the bc plane and posses an impressively short intermolecular C(sp³)?O(sp³) contact.     

Viscosity of aqueous mixtures of silver and thallium nitrates with calcium or cadmium nitrates from pure fused salt to pure water

Fused salt-water systems extending from pure fused salt to pure water have been less studied than dilute aqueous solutions, despite their practical and theoretical importance. Even fewer studies have been made regarding the influence of the temperature upon transport properties. The present publication brings new interesting information on the viscous flow properties of the following two fused nitrate-water systems containing monovalent and divalent cations: AgNO₃–TINO₃–M(NO₃)₂–H₂O where M=Ca or Cd, with the TINO₃ and M(NO₃)₂ mole fractions in the anhydrous salt fixed at 0.436 and 0.100, respectively. The parameters in the Arrhenius, Eyring, Batschinski and the Abraham and Abraham equations are found to be well correlated with the properties of the components of the melts. The temperature effect allows a discussion to be made in terms of structural features such as holes and free volumes.     

Carbonyl-yne reactions of 3,3,3-trifluoropyruvates

An efficient synthesis of trifluoromethyl-containing 2,3-allenols via carbonyl-yne reaction of 3,3,3-trifluoropyruvates with acetylenes is described. In the presence of MgBr₂·Et₂O the reaction of methyl trifluoropyruvate with hex-1-yne proceeds diastereoselectively. Trifluoromethyl-substituted 2,3-allenols can be stereoselectively transformed into trifluoromethyl-substituted 2,5-dihydrofurans on treatment with AgNO₃.     

Bestimmung von Thiolgruppen mit AgNO3, NÄM und PCMB unter Anwendung der amperometrischen Titration

An indirect method for the determination of SH groups which is also applicable to undissolved material and proteins with sluggish reacting SH groups is described: The sample containing 0.2–0.8 ΜMol thiol is first incubated with 1.0 ΜMol of SH reagent [AgNO₃, N-ethylmaleimide (NEM) or p-chloromercuribenzoate (PCMB)] and after the reaction mixed with 1.0 ΜMol of SH-glutathion. The glutathion remaining after the binding of the excessive SH reagent is finally titrated amperometrically with a 10^?3 M AgNO₃ solution at pH 7.4. This method permits a great variety both of reaction conditions and the type of the primarily used SH reagent. Comparative determinations of SH groups using AgNO₃ were carried out with various low molecular SH compounds, with muscle tissue and bovine hemoglobin. AgNO₃ is suitable for the determination of SH groups in proteins and in glutathion, but not in cysteine, cysteine ethyl ester and 3-mercaptopropionic acid, since the mercaptides of these form complexes with Ag⁺ ions. The application of NEM and PCMB is recommended generally for checking and completing the results obtained with AgNO₃.     

Copper(II)/Palladium(II) catalysed highly selective cross-coupling of terminal alkynes in supercritical carbon dioxide

An efficient protocol for the synthesis of unsymmetrical 1,3-diynes was developed using supercritical carbon dioxide (ScCO₂) as the solvent. The direct coupling of two different terminal alkynes is catalysed by a bimetallic catalyst, CuCl₂·2H₂O/Pd(NH₃)₄Cl₂·H₂O, in the presence of the base tetramethylethylenediamine (TMEDA) and O₂. In pure ScCO₂, our bimetallic catalytic system maintains high activity over a wide substrate scope to provide unsymmetrical 1,3-diynes in good to excellent yields. In the proposed reaction mechanism, the synergistic cooperation between copper(II) and palladium(II) centres is responsible for the superior selectivity of the cross-coupling.     

Micellization and morphological characterization of Ag-micelles prepared by poly(vinyl acetate)–silver nitrate in solvent/nonsolvent system

The inducing method for preparing Ag-micelle solution with the use of mixed solvent/nonsolvent, and the morphological characterization of the generated metal–micelles were investigated and reported in this paper. In this method, an Ag containing metal chelate polymer (MCP) raw solution was preprepared by dissolving poly(vinyl acetate) (PVAc)–silver nitrate (AgNO₃) MCP in conc. formic acid, and a mixed solvent of HCOOH/H₂O with specific water composition was then added to induce the micellization of the MCP chain. The critical water concentration (CWC) that was needed for inducing the formation of the Ag-micelles, and the water concentration at which the flocculation of the Ag-micelles occurred in micellar solution, were studied by measuring the transmittance of the dilute MCP solution; the results showed that a long-lasting MCP solution with stable micelles might be prepared by using a H₂O/HCOOH solvent of specific weight ratio 1:1.2. The effect of the AgNO₃ concentration on the morphology of the Ag-micelles was also investigated by transmission electron microscopy (TEM). At AgNO₃ concentration below 0.5 wt%, the Ag-micelles displayed a variety of core-shell structure; but as the AgNO₃ concentration was increased to 1.0–2.0 wt%, micelles that had Ag-solid embedded in the micellar core were observed.