Synthesis of both epimeric triacid ananlogs of kainic acid

A practical and cheap method for synthesis of C-4 carboxylic acid substituted kainic acid analogue 5 and its epimer 6 from trans-4-hydroxyproline is described. Using this method, more interesting intermediates and analogues could be obtained easily.     

二[氧合-二(3-二茂铁基丙烯酸二正丁基锡(Ⅳ))]配合物的合成及谱学表征

由FcCH=CHCO2H和(n Bu)2SnO反应合成了{[(FcCH=CHCO2)Sn(n Bu)2]2O}2(A)新配合物[其中Fc=(η5 C5H5)Fe(η5 C5H4)].经红外光谱和核磁共振(1H、13C、119Sn)谱学研究, 确定其组成和结构.提出 [(RCOOSnR′2)2O]2类化合物中一一指认与内环锡、外环锡键连的两类烷基R′中各个碳峰的原则.     

Breakage of λ-DNA by inorganic tin and organotin compounds as environmental pollutants

In proportion to the environmental pollution problems caused by organotin compounds, the genotoxicities of tin compounds in the environments have become of interest so as to estimate their safety in recent years. In this work, isolated λ-DNA (double-strand DNA) was incubated with inorganic tin(II) and tin(IV) and five organotin compounds [n-butyltin trichloride, di(n-butyltin) dichloride, methyltin trichloride, dimethyltin dichloride and trimethyltin chloride] in reaction systems both with and without hydrogen peroxide (H₂O₂) content. The tin compounds tested in this study did not induce DNA breakage in the absence of hydrogen peroxide. Divalent inorganic tin (SnCl₂) and tetravalent inorganic tin (SnCl₄) caused DNA breakage in the presence of hydrogen peroxide (10 mM), and the DNA damage activity of inorganic tin was much more potent in divalent inorganic tin (SnCl₂) than in tetravalent inorganic tin (SnCl₄). Divalent inorganic tin (SnCl₂) induced DNA breakage in a concentration-dependent fashion at concentrations greater than 0.1 mM of SnCl₂ in the presence of hydrogen peroxide (10 mM). DNA breakage was not caused by n-butyltin compounds and methyltin compounds either in the presence or in the absence of hydrogen peroxide.     

Preparation of Nanosize Tin Oxide Particles from Water-in-Oil Microemulsions

Nanoparticles of tin oxide (SnO2) have been prepared from water-in-oil microemulsions consisting of water, AOT (surfactant), and n-heptane (oil). Precursor hydroxides were precipitated in the aqueous cores of water-in-oil microemulsions and then calcined at 600 degrees C for 2 h to form tin oxide powder. The formation of phase pure tin oxide was confirmed by means of X-ray diffraction analysis. The tin oxide powder was found to be less than 40 nm in particle diameter and to have a higher specific surface area, about 73 m2/g, when compared with tin oxide powder prepared through the conventional precipitation method (19 m2/g). Copyright 1999 Academic Press.     

Synthesis of di-μ-OXO-tetra-（α-pentyloxy） tin（Ⅳ） phthalocyanine

Axially substituted tin phthalocyanines, namely dichloride-tetra-（α-pentyloxy） tin （Ⅳ） phthalocyanine 2, dihydroxy-tetra-（α-pentyloxy） tin （Ⅳ） phthalocyanine 3 and its dimmer di-μ-oxo-tetra-（α-pentyloxy） tin（Ⅳ） phthalocyanine 4 were synthesized. The catalytic effect of H2O-free CaCl2 in quinoline was used for condensation of dihydroxy tin phthalocyanine 3 to the cofacially array dimmer 4. Their structures were characterized by UV-vis, IR, elemental analysis, MS, as well as ^1HNMR spectroscopy.     

石墨炉原子吸收光谱法测定锡和锗时基体改进剂硝酸钙的作用

石墨炉原子吸收光谱法测定低温易挥发元素锡和锗时灵敏度较低。本文以硝酸钙为基体改进剂,使锡和锗的灵敏度分别比不加基体改进剂时提高9倍和50倍,同时也显著提高灰化温度,并降低原子化温度。本文也探讨了基体改进剂硝酸钙对锡和锗的增感机理。锡的增感是由于固相和气相中钙的作用,而锗的增感仅是气相钙的作用。     

(Salen)tin complexes: syntheses, characterization, crystal structures, and catalytic activity in the formation of propylene carbonate from CO(2) and propylene oxide

A series of (salen)tin(II) and (salen)tin(IV) complexes was synthesized. The (salen)tin(IV) complexes, (salen)SnX(2) (X = Br and I), were prepared in good yields via the direct oxidation reaction of (salen)tin(II) complexes with Br(2) or I(2). (Salen)SnX(2) successfully underwent the anion-exchange reaction with AgOTf (OTf = trifluoromethanesulfonate) to form (salen)Sn(OTf)(2) and (salen)Sn(X)(OTf) (X = Br). The (salen)Sn(OTf)(2) complex was easily converted to any of the dihalide (salen)SnX(2) compounds using halide salts. All complexes were fully characterized by (1)H NMR spectroscopy, mass spectrometry, and elemental analysis, while some were characterized by (13)C, (19)F, and (119)Sn NMR spectroscopy. Several crystal structures of (salen)tin(II) and (salen)tin(IV) were also determined. Finally, both (salen)tin(II) and (salen)tin(IV) complexes were shown to efficiently catalyze the formation of propylene carbonate from propylene oxide and CO(2). Of the series, (3,3',5,5'-Br(4)-salen)SnBr(2), 3i, was found to be the most effective catalyst (TOF = 524 h(-)(1)).     

Mechanism for the formation of tin oxide nanoparticles and nanowires inside the mesopores of SBA-15

The formation of polycrystalline tin oxide nanoparticles (NP) and nanowires was investigated using nanocasting approach included solid-liquid strategy for insertion of SnCl₂ precursor and SBA-15 silica as a hard template. HR-TEM and XRD revealed that during the thermal treatment in air 5 nm tin oxide NP with well defined Cassiterite structure were formed inside the SBA-15 matrix mesopores at 250 °C. After air calcination at 700 °C the NP assembled inside the SBA-15 mesopores as polycrystalline nanorods with different orientation of atomic layers in jointed nanocrystals. It was found that the structure silanols of silica matrix play a vital role in creating the tin oxide NP at low temperature. The pure tin chloride heated in air at 250 °C did not react with oxygen to yield tin oxide. Tin oxide NP were also formed during the thermal treatment of the tin chloride loaded SBA-15 in helium atmosphere at 250 °C. Hence, it is well evident that silanols present in the silica matrix not only increase the wetting of tin chloride over the surface of SBA-15 favoring its penetration to the matrix pores, but also react with hydrated tin chloride according to the proposed scheme to give tin oxide inside the mesopores. It was confirmed by XRD, N₂-adsorption, TGA-DSC and FTIR spectra. This phenomenon was further corroborated by detecting the inhibition of SnO₂ NP formation at 250 °C after inserting the tin precursor to SBA-15 with reduced silanols concentration partially grafted with tin chloride.     

氧化锡表面的原子簇模型计算

Cluster models of SnO2(110) face and oxygen vacancies and oxygen adsorption on its surface have been calculated by EHMO method. The results show that a tin atom with a coordination number of four is the adsorption center, because the total energy of cluster model becomes lower when an oxygen atom adsorpts on the tin atom with a coordination number of four. The tin atom with this coordination number gains and loses electrons more easily than tin atoms with a coordination number of five. All tin atoms in the cluster of SnO2(110) face are Sn4+.     

Effect of pentaerythritol and organic tin with calcium/zinc stearates on the stabilization of poly(vinyl chloride)

The stabilization effect of calcium and zinc stearates (CaSt₂/ZnSt₂) combined with pentaerythritol (PeE) and organic tin on poly(vinyl chloride) was investigated. The results show that the addition of calcium/zinc stearates combined with PeE and organic tin can improve thermal and colour stability of poly(vinyl chloride) in both static and dynamic tests. Mechanisms for improving stability of PVC are also discussed. The increase of stabilizing effectiveness of calcium/zinc stearates is ascribed to the synergistic effect between CaSt₂/ZnSt₂ and PeE and the interaction between organic tin and double bonds formed during the degradation of PVC. There is no synergistic action between organic tin and PeE or organic tin and calcium/zinc stearates.     

Carbonyl allylations by allylic chlorides utilizing a reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources

Carbonyl allylations by allylic chlorides either with tin(IV) iodide and tetrabutylammonium iodide (TBAI) in dichloromethane or with tin(IV) iodide and sodium iodide in 1,3-dimethylimidazolidin-2-one at room temperature produced the corresponding homoallylic alcohols. The carbonyl allylations probably proceeded via the reduction of tin(IV) iodide to triiodostannate(II) species with iodide sources such as TBAI and NaI, which led to the construction of a tin(IV)-catalytic cycle based on regeneration of tin(IV) iodide via the transmetalation of homoallyloxytriiodotin to homoallyloxytrimethylsilane with iodotrimethylsilane.     

A New Tin Graphite Intercalation Compound for Lithium Ion Batteries

IntroductionLithium ion batteries have attracted a great interestbecause of their commercial applications in portable de-vices[1,2].Great efforts have been made to improve theenergy density of new anode materials.For example,Sn-based compounds,such as SnO…     

Darstellung und strukturen von cyclischen tristanna-dichalkogen-verbindungen

Cyclic tin chalcogen compounds with tintin bonds (t-Bu₂Sn)₃Y₂ (Y  S, Se, Te) have been prepared starting with (t-Bu₂Sn)₄ or (t-Bu₂SnY)₂. X-Ray analysis shows planar five-membered tin-sulfur rings and tin-selenium rings. The structure of the tellurium compound consists of puckered molecules with C₂ symmetry and a somewhat shorter tintin bond.     

Synthesis of di-μ-oxo-tetra-(α-pentyloxy)tin(Ⅳ)phthalocynine

Axially substituted tin phthalocyanines, namely dichloride-tetra-(pentyloxy) tin (IV) phthalocyanine 3 and its dimmer di-cyanine 4 were synthesized. The catalytic effect of H2O-free CaCl2 in quinoline was used for condensation of dihydroxy tin phthalocyanine 3 to the cofacially array dimmer 4. Their structures were characterized by UV-vis, IR, elemental analysis, MS, as well as 1HNMR spectroscopy.     

Sulfonate-bonded tin complexes for the production of diphenyl carbonate

Various tin complexes including dibutyltin oxide and dibutyltin diacetate were tested for their activities in the transesterification between dimethyl carbonate (DMC) and phenol to produce diphenyl carbonate (DPC). The activities of tin complexes were significantly enhanced by the co-presence of alkyl or arylsulfonic acid, possibly due to the in situ formation of sulfonate-bonded tin complexes. Highly active triflate-bonded tin species, [Bu₂Sn(OH)(OTf)]₂ and [Bu₂Sn(OAc)(OTf)]₂, were isolated from the reaction of triflic acid with dibutyltin oxide and dibutyltin diacetate, and characterized by single crystal X-ray diffraction study.     

Regio- and diastereocontrol in carbonyl allylation by 1-halobut-2-enes with Tin(II) halides

Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are described. Tin(II) bromide in a dichloromethane-water biphasic system is an effective reagent for unusual alpha-regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-en-1-ols. The addition of tetrabutylammonium bromide (TBABr) to the biphasic system produces 1-substituted 2-methylbut-3-en-1-ols via usual gamma-addition which is opposite to the alpha-addition without TBABr. The gamma-addition to aromatic aldehydes exhibits anti-diastereoselectivity, while that to aliphatic aldehydes is not diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does proceed with tin(II) iodide and exhibits gamma-syn selectivity which is unusual for a Barbier-type carbonyl allylation. In the carbonyl allylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of tetrabutylammonium iodide (TBAI) accelerates the reaction and enhances gamma-syn selectivity. The use of tin(II) iodide and TBAI produces 2-methyl-1-phenylbut-3-en-1-ol with high yield and high syn-diastereoselectivity. The syn-diastereoselective carbonyl allylation of 1-chlorobut-2-ene using tin(II) iodide, a catalytic amount of TBAI, and NaI in DMI-H(2)O is applied to various aldehydes.     

基于层状二硫化钼纳米片比色检测亚锡离子

在醋酸/醋酸钠缓冲溶液(pH=4.5)中, 亚锡离子对层状二硫化钼(MoS₂)纳米片催化过氧化氢(H₂O₂)氧化邻苯二胺(OPD)的显色反应有很强的抑制作用, 据此构建了一种检测亚锡离子的比色传感器. 实验结果表明, 与不加MoS₂纳米片的OPD/H₂O₂比色传感体系相比, MoS₂/OPD/H₂O₂体系检测亚锡离子的灵敏度显著提高, 线性范围变宽. 在优化的条件下, MoS₂/OPD/H₂O₂传感体系检测亚锡离子的线性范围为0.02~3.0 μmol/L, 检出限为8 nmol/L (S/N=3). 该传感体系对检测亚锡离子具有高的选择性, 可用于湖水中亚锡离子的检测.     

Methylation of inorganic tin by decaying spartina alterniflora in estuarine water and by estuarine water

Methyltin compounds (MeSn) which do not originate from man–made pollution are common in estuaries and particularly in salt marshes containing the marsh grass Spartina alterniflora. This study reports the results of experiments in which estuarine water containing S. alterniflora leaves is spiked with inorganic tin, and estuarine water alone is spiked with inorganic tin and MeSn. When decaying leaves are present, inorganic tin concentrations in the water decrease and there is a 10-fold increase in inorganic tin concentration in the leaves. This biosorption follows pseudo–first–order kinetics. MeSn³⁺ and Me₂Sn²⁺ occur occasionally in the water. The Me₂Sn²⁺ concentration decreases with time and the Me₃Sn²⁺ concentration increases with time in S. alterniflora leaves. The results of estuarine water amended with inorganic tin and MeSn in the absence of leaves are quite different. The overall inorganic tin concentration decreases significantly during the experiment, the MeSn³⁺ concentration is approximately constant, and concentrations of Me₂Sn²⁺ and Me₃Sn⁺ increase. This means that net methylation of inorganic tin has occurred. We conclude that decaying S. alterniflora is likely to be important in the cycling of tin in salt marshes.     

The complexometry of tin(IV)

Tin(IV) very readily hydrolyses in solution, and forms hydrous tin oxide SnO(2)2.nH(2)O even in rather strongly acidic solution. In spite of a lack of reliable data on the hydrolysis of tin(IV) a consistent picture of the behaviour of tin(IV) in solution has been constructed. Some values for the formation of hydroxide and chloride complexes were deduced from electrochemical data. In agreement with more or less qualitative remarks by other investigators a value of log k(so) = -3 has been found for the solubility constant. For the stability constant of tin(IV)-EDTA, log K(SnY) = 34.5 was found experimentally. A survey is given of the pitfalls which exist in handling tin solutions. A back-titration procedure is presented that provides for the complexometric determination of tin(IV) at concentrations down to 3 ppm, with an error of 1% or better. Thorium is used as back-titrant with Semi-Xylenol Orange as indicator. The method has successfully been applied to the analysis of organotin compounds.     

Preconcentration by coprecipitation of arsenic and tin in natural waters with a Ni-pyrrolidine dithiocarbamate complex and their direct determination by solid-sampling atomic-absorption spectrometry

A method for the determination of trace amounts of arsenic and tin in natural waters is described. Trace amounts of arsenic and tin were preconcentrated by coprecipitation with a Ni-ammonium pyrrolidine dithiocarbamate (APDC) complex. The coprecipitates obtained were directly analyzed by graphite-furnace atomic-absorption spectrometry (GFAAS) using the Ni-APDC complex solid-sampling technique. The coprecipitation conditions used for the trace amounts of arsenic and tin in natural water were investigated in detail. It was found that arsenic and tin at sub-ng mL(-1) levels were both coprecipitated quantitatively by Ni(PDC)2 in the pH range 2-3. The concentration factors by coprecipitation reached approximately 40,000 when 2 mg nickel was added as a carrier element to 500 mL of the water sample. The proposed method has been applied to the determination of trace amounts of arsenic and tin in river water and seawater reference materials, and the detection limits for arsenic and tin, which were calculated from three times of the standard deviation of the procedural blanks, are 0.02 ng mL(-1) and 0.04 ng mL(-1), respectively, for 500-mL volumes of water sample.