Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Synthese und Kristallstrukturen der Phosphanimin-Komplexe MCl2(Me3SiNPMe3)2 mit M = Zn und Co,und CoCl2(HNPMe3)2

Syntheses and Crystal Structures of the Phosphaneimine Complexes MCl₂(Me₃SiNPMe₃)₂ with M = Zn and Co, and CoCl₂(HNPMe₃)₂ The molecular complexes MCl₂(Me₃SiNPMe₃)₂ (M = Zn, Co) have been prepared by the reaction of the dichlorides of zinc and cobalt with Me₃SiNPMe₃ in CH₃CN and CH₂Cl₂, respectively, whereas the complex CoCl₂(HNPMe₃)₂ has been prepared by the reaction of CoCl₂ with NaF in boiling acetonitrile in the presence of Me₃SiNPMe₃. All complexes were characterized by IR spectroscopy and by crystal structure determinations. The complexes MCl₂(Me₃SiNPMe₃)₂ crystallize isotypically. ZnCl₂(Me₃SiNPMe₃)₂: Space group P2₁2₁2₁, Z = 4, 2677 observed unique reflections, R = 0.024. Lattice dimensions at ?70°C: a = 1243.6; b = 1319.0; c = 1464.7 pm. CoCl₂(Me₃SiNPMe₃)₂: Space group P2₁2₁2₁, Z = 4, 3963 observed unique reflections, R = 0,071. Lattice dimensions at ?80°C: a = 1236.3; b = 1317.4; c = 1457.6 pm. CoCl₂(HNPMe₃)₂ · CH₂Cl₂: Space group Pbca, Z = 8, 1354 observed unique reflections, R = 0.055. Lattice dimensions at ?80°C: a = 1247.3; b = 998.4; c = 2882.4 pm. All complexes have monomeric molecular structures, in which the metal atoms are coordinated in a distorted tetrahedral fashion by the two chlorine atoms and by the nitrogen atoms of the phosphaneimine molecules.     

FLAVIN SENSITIZED PHOTOOXIDATION OF (POLY)AMINO ACIDS: FATE OF THE PHOTOSUBSTRATE

Abstract— With respect to literature data, which seemed to be contradictory, we examined the fate of ethylenediaminetetraacetate (EDTA) and nitrilotriacetate (NTA) in flavin-sensitized photooxidation reactions by quantitation of all possible products, i.e. CO₂ by acidimetric titration, CH₂O by colometry and glyoxylate enzymatically; N-methyl groups were quantified by ₁H-NMR. Nitrilotriacetate yields 100% oxidative photodecarboxylation with CH₂O formation, while EDTA behaves quite differently, yielding quantitative amounts of CO₂ and glyoxylate, but no CH₂O. The electron balance in this reaction is found to be maintained by co-formation of one equivalent >N-CH₃. From these data it is concluded that the photooxidation of the structural element >NCH₂C0₂ containing a tertiary nitrogen atom, occurs by electron transfer, followed by decarboxylation. The neutral radical that is formed is reductant and will give off an electron equivalent to yield the easily hydrolysed structural element >N⁺= CH₂. With EDTA, containing the fragment –O₂CCH₂ >NCH₂CH₂N< CH₂CO₂–, the electron transfer towards flavin is strongly favoured by stabilisation of a cisoid mesomeric radical cation (₀₂cch₂ >₊ NCH₂CH₂N_CH2CO2 o₂cch₂ >NCH₂CH₂N_+CH2CO2), which, after loss of CO₂ undergoes internal 1,6-hydrogen shift to yield the more stable radical: _CH2>CH₂CH₂N CH₂CO₂CH₂lt NCH₂CH₂N_HCO2. The latter radical will easily be oxidized to the iminium ion >N_*= CH-C0_2-. which in turn hydrolyses to glyoxylate. Chelation of EDTA by metal cations prevents the 1,6-hydrogen shift, and leads to the product pattern obtained in the NTA photoreaction.     

Reactions of magnesium formate on supports

Thermal decomposition of supported magnesium formate has been studied by gas chro-matography.The reaction paths of decomposition of supported magnesium formate depend on thenature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst togive CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanationreaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leadsto the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears aftermodified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2~- takes place on thesurface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of COand only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the firstpeak of CO_2 arises from the reaction of surface Mg~(2+) with HCO_2~- from dissociated Mg(HCO_2)_2.     

Darstellung von polyfluororganotrichlorsilanen

The following substances could be prepared by Grignard reactions or by conversions with trichlorosilane: C₆F₅CH₂CHCH₂, C₆F₅(CH₂)₃SiCl₃, CF₃(CF₂)₉CH₂CHCH₂, CF₃(CF₂)₇(CH₂)₂SiCl₃, CF₃(CF₂)₁₁(CH₂)₃CHCH₂ und CF₃(CF₂)₁₁(CH₂)₅SiCl₃.They were characterized by spectroscopical and microanalytical methods.     

Author index

The thermal decomposition of N₂H₅Nd(SO₄)₂·H₂O has been studied by simultaneous TG and DSC and by isothermal weight change determination. The final product and the intermediate phases have been identified by chemical analysis, X-ray powder patterns and infrared spectroscopy. The solid phases in the decomposition sequence are: N₂H₅Nd(SO₄)₂· H₂O → N₂H₅Nd(SO₄)₂ → NH₄Nd(SO₄)₂ → Nd₂(SO₄)₃. The reactions overlap under dynamicconditions, isothermally, however, NH₄Nd(SO₄)₂ can be obtained by 200°C.     

Aminoderivate hydrierter Oligosilane: Darstellung,Charakterisierung und Eigenschaften

Summary Amino derivatives of linear and branched tri- und tetrasilanes R₂N-H₂Si(SiH₂)SiH₂-NR₂ H₃SiSiHNR₂SiHNR₂SiH₃, R₂N-H₂SiSiH₂SiH₂SiH₂-NR₂ und (R₂N-H₂Si)₂SiHSiH(SiH₂-NR₂)₂ with R = Et, SiMe₃ are formed by the reaction of the corresponding bromooligosilanes with suitable amines or alkali metal amides. Product distribution and yields are strongly influenced by the nucleophilicity of the amino reagent and by the structure of the SiSi-backbone. The structures proposed for the aminopolysilanes thus prepared are proved by²⁹Si-,¹H-NMR-and MS-investigations.

     

The √t law in solid-phase reactions. Analysis of the hypothesis on rate constant distribution

The reaction C₂H₅ + O₂ → C₂H₅O₂ in glassy methanol-d₄ and the H-atom abstraction by CH₃, C₂H₅, and n-C₄H₉ radicals in C₂H₅OH + C₂D₅OH and CD₃CH₂OH + C₂D₅OH glassy mixtures have been studied by electron spin resonance. The analysis of the dependence of the reaction rates on the concentration of O₂ (oxidation) and C₂H₅OH, CD₃CH₂OH (H-atom abstraction) has shown that the √t law is not conditioned by the existence of regions characterized by different rate constants.     

Low oxidation state ruthenium chemistry : IV. The reactions of M(CO)2(PPh3)3 complexes (M = Fe,Ru) and the hydrogenation and isomerization of alkenes catalyzed by RuL(CO)2(PPh3)2 (L = H2, PPh3)

The complexes M(CO)₂(PPh₃)₃ (I, M = Fe; II, M = Ru) readily react with H₂ at room temperature and atmospheric pressure to give cis-M(H)₂(CO)₂(PPh₃)₂ (III, M = Fe;IV,M = Ru). I reacts with O₂ to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis-Ru(O₂)(CO)₂(PPh₃)₂(V). Even compound IV reacts with O₂ to give V with displacement of H₂; this reaction has been shown to be reversible and this is the first case where the displacement of H₂ by O₂ and that of O₂ by H₂ at a metal center has been observed. III and IV are reduced to M(CO)₃(PPh₃)₂ by CO with displacement of H₂; Ru(CO)₃- (PPh₃)₂ is also formed by treatment of IV with CO₂, but under higher pressure. Compounds II and IV react with CH₂CHCN to give Ru(CH₂CHCN)(CO)₂- (PPh₃)₂(VI) which reacts with H₂ to reform the hydride IV.cis-Ru(H)₂(CO)₂(PPh₃)₂(IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H₂ and O₂ on the “Ru(CO)₂(PPh₃)₂” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO)₂(PPh₃)₃(II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere.     

Preparation and activity evaluation of relative p–n junction photocatalyst Co-TiO<Subscript>2</Subscript>/TiO<Subscript>2</Subscript>

Co-TiO₂ photocatalyst was prepared by a sol–gel method using Co(NO₃)₂ · 6H₂O and tetrabutyl titanate [Ti(OC₄H₉)₄] as raw materials, and Co-TiO₂/TiO₂ photocatalyst was synthesized by mixing the Co-TiO₂ sol with TiO₂ sol. The Co-TiO₂/TiO₂ was characterized by X-ray powder diffraction, UV–Vis diffuse reflection spectrum, scanning electron microscopy, transmission electron microscopy, fluorescence spectra and X-ray photoelectron spectroscopy. The photocatalytic activity of the photocatalyst was evaluated by photocatalytic reduction of Cr₂O₇ ²⁻ and photocatalytic oxidation of methyl orange under UV irradiation. The results showed that, for the photocatalytic reduction of Cr₂O₇ ²⁻, the optimum percentage of Co-doped for the Co-TiO₂ was 0.5% (mole ratio of Co/Ti), and the optimum percentage of Co-TiO₂ for the Co-TiO₂/TiO₂ was 2.0% (mole ratio of Co-TiO₂/TiO₂). The photocatalytic reduction activities of the Co-TiO₂/TiO₂ and Co-TiO₂ are much higher than that of TiO₂. However, the photocatalytic oxidation activities of the Co-TiO₂/TiO₂ and Co-TiO₂ are much lower than that of TiO₂. Effects of heat treatment on the photocatalytic activities of the Co-TiO₂/TiO₂ and Co-TiO₂ were investigated. The mechanisms of influence on the photocatalytic activity were also discussed.     

静电自组装制备纳米TiO2/SiO2光催化材料

采用静电自组装方法制备了纳米TiO2/SiO2光催化材料。采用巯丙基三甲氧基硅烷偶联剂对SiO2进行干法改性,采用双氧水/冰醋酸将偶联剂巯基基团氧化为磺酸基基团。在正负电荷的吸引下,带负电荷的SiO2与带正电荷的钛聚合阳离子自发地组装在一起,经一定温度热处理得到纳米TiO2/SiO2光催化材料。采用XRD、FTIR、PL、UV-Vis DRS、SEM和ICP等对材料进行了分析和表征。采用甲基橙溶液评价材料的光催化性能。结果表明:SiO2促使锐钛矿的形成,抑制锐钛矿向金红石的转变,减小TiO2的晶粒尺寸,使得TiO2光吸收波长发生蓝移。TiO2与SiO2通过Si-O-Ti键发生结合。采用静电自组装方法制备的材料中TiO2的含量高于传统方法,导致材料的光催化性能有所提高。     

The steric and electronic effects of aliphatic fluoroalkyl groups

Ab initio calculations were performed on 18 fluorinated and unfluorinated alcohols at the B3LYP and HF levels with the 6-311G^∗∗ basis set. Molar volumes of the alcohols were computed at each level and averaged to produce a scale of relative size. From this, various isosteric replacements of potential use in drug design were suggested: ethyl by FCH₂CH₂ or HCF₂CH₂, propyl by CF₃CH₂, isopropyl by CF₃(CH₃)CH or (FCH₂)₂CH, isobutyl or t-butyl by (CF₃)₂CH, and 3-methyl-2-butyl by CF₃(CH₃)₂C. Calculation of the charge on oxygen and the Wiberg index of the CO bond allowed an electronegativity scale to be constructed for the fluoroalkyl groups. Electronegativity decreased in the order: (CF₃)₃C>(CF₃)₂CH>C₂F₅CH₂>CF₃CH₂>CH₃(CF₃)₂C>HCF₂CH₂>CF₃(CH₃)CH>(FCH₂)₂CH>FCH₂CH₂>CF₃(CH₃)₂C. This ranking agreed with literature acid dissociation data for the alcohols studied.     

Chemical characterization of plasma-polymerized films from acetylene and nitrogen-containing mixtures and their ethanol vapor sensitivity

In this study, plasma-polymerized thin films were prepared from plasma enhanced chemical vapor deposition (PECVD) of acetylene (C₂H₂), acetylene/nitrogen (C₂H₂/N₂), or acetylene/ammonia (C₂H₂/NH₃). When N₂ or NH₃ was mixed with C₂H₂ in the feed, the films were identified to contain all elements of the mixture and the properties of the films were implied by the C–H bonds and nitrogen functionalities. As shown by X-ray photoelectron spectroscopy (XPS) the [N]/[C] atomic ratio varies by changing the mixture composition and reaches a maximum of 0.12 for mixing C₂H₂ with NH₃. It is found that the resistance of the thin film sensors prepared from C₂H₂, C₂H₂/N₂, and C₂H₂/NH₃ is distinctly decreased by over 2 orders of magnitude by the adsorption of ethanol vapor.     

Synthesis and characterization of organotin complexes with dithiocarbamates and crystal structures of (4‐NCC6H4CH2)2Sn(S2CNEt2)2 and (2‐ClC6H4CH2)2 Sn(Cl)S2CNBz2

Ten organotin derivatives with dithiocarbamates of the formulae (4‐NCC₆H₄CH₂)₂Sn(S₂CNEt₂)₂ (1), (4‐NCC₆H₄CH₂)₂Sn(S₂CNBz₂)₂ (2), (4‐NCC₆H₄CH₂)₂Sn[S₂CN(CH₂CH₂)₂NCH₃]₂ (3), (2‐ClC₆H₄CH₂)₂ Sn(S₂CNEt₂)₂ (4), (2‐ClC₆H₄CH₂)₂Sn(S₂CNBz₂)₂ (5), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CNEt₂ (6), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CNBz₂ (7), (4‐NCC₆H₄CH₂)₂Sn(Cl)S₂CN(CH₂CH₂)₂NCH₃ (8), (2‐ClC₆H₄CH₂)₂ Sn(Cl)S₂CNEt₂ (9) and (2‐ClC₆H₄CH₂)₂Sn(Cl)S₂CNBz₂ (10) have been prepared. All complexes were characterized by elemental analyses, IR and NMR. The crystal structures of complexes 1 and 10 were determined by X‐ray single crystal diffraction. For complex 1, the central tin atom exists in a skew‐trapezoidal planar geometry defined by two asymmetrically coordinated dithiocarbamate ligands and two 4‐cyanobenzyl groups. In addition, because of the presence of close intermolecular non‐bonded contacts, complex 1 is a weakly‐bridged dimer. In complex 10, the central tin atom is rendered pentacoordinated in a distorted trigonal bipyramidal configuration by coordinating with S atoms derived from the dithiocarbamate ligand. In vitro assays for cytotoxicity against five human tumor cell lines (MCF‐7, EVSA‐T, WiDr, IGROV and M226) furnished the significant toxicities of the title complexes. Copyright © 2006 John Wiley & Sons, Ltd.     

Attempts to prepare alkylidene zirconium complexes by α-hydrogen atom abstraction

We prepared several new neopentyl halide complexes of zirconium in order to test whether they could be induced to lose neopentane and give neopentylidene complexes by adding phosphorus or nitrogen donor ligands. ZrNp₂X₂ (X  Cl or Br) can be prepared in ether and isolated as a dietherate (an oil). It reacts with L (L  PMe₃, PMe₂Ph, NEt₃, $\text{1}\text{2}$ DMPE, $\text{1}\text{2}$ TMEDA) to give ZrNp₂X₂L₂. ZrNp₃Cl can be prepared by adding MgNp₂ to ZrNp₂Cl₂(ether)₂ and isolated by sublimation in 25% yield. On adding PMe₃ or TMEDA, it disproportionates to ZrNp₄ and ZrNp₂Cl₂L₂. ZrCp″NpCl₂ (Cp″ = η⁵-C₅Me₅), ZrCp″Np₂Cl, and ZrCp″Np₃ were prepared by adding MgNp₂ to ZrCp″Cl₃. Only the last is a solid, only the first forms an adduct, ZrCp″NpCl₂(PMe₃). None of the complexes decomposed to tractable products in the presence of L. Photolysis of ZrNp₂Cl₂(PMe₃)₂ yielded [Zr(PMe₃)₂Cl₃]₂ by an apparently complex reaction initiated by homolytic ZrNp bond fission.     

Synthesis,characterization, crystal structure,and reactivity of heterobimetallic dioxovanadium(V) complexes containing multidentate hydrazone ligands

Two new heterobimetallic complexes of the composition [(VO₂)₂(μ₃-slsch){Na₂(μ-H₂O)₂(H₂O)₂}]_n (1) and [(VO₂)₂(μ₃-npsch){Na₂(μ-H₂O)₂(H₂O)₂}(DMF)]_n (2) were obtained by reaction of the ligand and vanadium pentoxide in a 1:1 molar ratio in methanol in the presence of Na₂CO₃ (2 equivalents). The complexes obtained were characterized using various spectroscopic studies. The structures of both the complexes were established by single crystal X-ray crystallographic study. We have also explored the catalytic behavior of the complexes in oxidative bromination of phenol red, which is the bio-inspired reaction catalyzed by an enzyme haloperoxidase.     

Synthese und Kristallstruktur von [(PhCH2)2GaF(tBuNH2)]2 · 2 THF

Synthesis and Crystal Structure of [(PhCH₂)₂GaF(^tBuNH₂)]₂ · 2 THF (PhCH₂)₂GaF reacts with ^tBuNH₂ to the adduct [(PhCH₂)₂GaF(^tBuNH₂)] ( 1 ). 1 was characterized by NMR, IR and MS techniques. 1 can be recrystallized from THF forming crystals of [ 1 ]₂ · 2 THF. According to an X-ray structure analysis [ 1 ]₂ · 2 THF consists of dimers of 1 formed by hydrogen bridges. The THF molecules are coordinated to [ 1 ]₂ by hydrogen bridges, too.     

Base-catalyzed reactions enhanced by solid acids: Amine-catalyzed nitroaldol (Henry) reactions enhanced by silica gel or mesoporous silica SBA-15

The reactions of various aldehydes with CH₃NO₂ catalyzed by Et₃N, n-C₆H₁₃NH₂, and Me₂N(CH₂)₂NH₂ were accelerated by the addition of silica gel to give aromatic (aliphatic) β-nitroalcohols, aromatic nitroalkenes, and aromatic 1,3-dinitroalkanes, respectively. Mesoporous silica SBA-15 showed higher activity than silica gel for the synthesis of aromatic nitroalkenes by the reactions of the corresponding aldehydes with CH₃NO₂ catalyzed by n-C₆H₁₃NH₂.     

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.     

Synthesis and Crystal Structure of [Ni(H2O)6][Ni(H2O)2(C4H2O4)]·4H2O

Reaction of a freshly prepared Ni(OH)_{2?2 x} (CO₃) _x ·yH₂O with maleic acid in H₂O at room temperature afforded [Ni(H₂O)₆][Ni(H₂O)₂(C₄H₂O₄)]·4H₂O, which consists of [Ni(H₂O)₆]²⁺ cations, [Ni(H₂O)₂(C₄H₂O₄)]^2? anions and lattice H₂O molecules. Ni atoms in cations are octahedrally coordinated and Ni atoms in anions are each octahedrally coordinated by bidentate chelating maleato ligands and two water molecules at trans positions. Cations and anions are interlinked by hydrogen bonds to form 1D chains, which are hexagonally arranged and connected by the lattice water molecules. When heated in a flowing argon stream, the compound decomposes, with complete dehydration being followed by dissociation of nickel maleate into NiO and maleic anhydride.