Selective substituent transfer from mixed zinc reagents in Ni-catalyzed anhydride alkylation

The use of mixed zinc reagents in Ni-catalyzed anhydride alkylation results in preferential transfer of substituents (Ph > Me > Et > iPr approximately TMSCH2) for the ligands bipy, dppe, and iPrPHOX. Utilization of such mixed species allows the use of 0.55 equiv of the diorganozinc reagent, effectively transferring both desired substituents when used in conjunction with a suitable second zinc reagent.     

Dicoordinate copper(I) silanechalcogenolates

The copper silanechalcogenolates tBu3PCuESiPh3 (1, E = O; 2, E = S; 3, E = Se) were prepared from the reaction of [tBu3PCu(CH3CN)3]BF4 with [Ph3SiELi(THF)2]2 in acetonitrile. The compounds were obtained as colorless, crystalline, but thermally labile solids. X-ray crystallography shows that complexes 1-3 are monomeric in the solid state with no Cu...Cu interactions. The Cu atoms have either a linear or a near-linear coordination geometry in all three complexes. Interestingly, the O atom in complex 1 is also linear, which is in contrast to the highly bent S (2) and Se analogues (3). Density functional theory calculations suggest that both the linear geometry of 1 and an associated extremely short Cu-O distance [1.769(4) A] are not the result of pi delocalization but are the result of a fine balance of electrostatic interaction and Pauli repulsion.     

Synthesis of stereoisomers of <Emphasis Type="Italic">p-tert</Emphasis>-butylthiacalix[4]arenes tetrasubstituted at the lower rim containing secondary amide groups and their complexation with a number of singly charged anions

The ability of new synthetic receptors, i.e., p-tert-butylthiacalix[4]arenes tetrasubstituted at the lower rim and containing secondary amide groups to form complexes with a number of spherical (F⁻, Cl⁻, Br⁻, I⁻), Y-shaped (MeCOO⁻), trigonal (NO₃ ⁻), and tetrahedral (H₂POO₄ ⁻) anions has been studied. It was shown that the nature of substituents on the nitrogen atom of the amide groups and configuration of the macrocycle affect the stability constant values of the forming complexes.     

Hard versus Soft Materials as Supports for Metallocene and Post‐Metallocene Catalysts

The influence of organic supports on the polymerization behavior of post‐metallocene catalysts is studied and compared with similarly supported titanium and zirconium metallocenes. The effects of the immobilization, activation, and polymerization process were studied by video microscopy, laser confocal fluorescence microscopy, SEM, and TEM. A model for the polymerization process for a catalyst supported on latex particles was developed from the results obtained. Organic supports based on latex particles are easily adjustable for different catalysts due to the versatile functionalization of the surfaces and can be applied to different types of olefin polymerization catalysts. They can be considered as an alternative to SiO₂ or MgCl₂ supports.

     

High-sensitivity, high-frequency extrinsic Fabry-Perot interferometric fiber-tip sensor based on a thin silver diaphragm

We propose and demonstrate a fiber-tip sensor based on an ultra-thin silver diaphragm for highly sensitive and high frequency ultrasonic detection. The diaphragm is prepared by the vacuum thermal deposition method and then transferred to the fiber tip. The sensor demonstrated in this letter has a 300 nm thick diaphragm with an inner diameter of 75 μm, leading to a static pressure sensitivity of 1.6 nm/kPa and a resonant frequency of 1.44 MHz. This sensor has potential applications in many fields such as structural health monitoring and medical ultrasonography.     

Arsenvergiftungen

The development of legal verification from torture via post mortem examination to chemical and radiochemical detection methods is shown by means of some spectacular cases of arsenic poisoning from the 17^th to the 20^th century. Because of the omnipresence of arsenic, it was not always possible to resolve all doubts.     

Confirmation of n-Hexane as an Inert Co-Solvent in the Production of Functionalized Silicon Nanoparticles from Reactive High-Energy Ball Milling

Alkanes such as n-hexane have been used as co-solvents in the production of functionalized semiconductor nanoparticles from alkenes and alkynes using Reactive High Energy Ball Milling (RHEBM) under the assumption that they are non-reactive under typical milling conditions. In this paper, a comparative study with two hydrocarbon solvents of comparable chain length, 1-hexyne, and n-hexane, and their milling products using three different commercially available silicon precursors, namely single crystal silicon wafers and polycrystalline particles having a nominal size of 4 µm and 1 mm, is reported. It is found that nanoparticle formation and surface functionalization in all the three silicon systems occurs only with 1-hexyne; n-hexane is non-reactive and does not lead to appreciable functionalized nanoparticle formation under the conditions studied. Nanoparticles (where formed) and microparticle byproducts of appropriate samples are characterized by Transmission electronic microscope (TEM), Fourier transform infrared  (FTIR), Photoluminiscence spectroscopy (PL), Nuclear magnetic resonance ¹H/¹³C NMR, and thermogravimetry TGA to separately confirm nanoparticle formation and surface functionalization.     

Design of a flexible but robust setup for temperature-dependent electrochemistry down to cryogenic temperatures

Electrochemistry and its analytics are essential in a variety of scientific and technological fields where properties related to reduction-oxidation reactions, so-called redox properties, are to be explored. While methodological standards for experiments are well established at room temperature, this is still untrue at sub-zero/cryogenic temperatures, the conditions required for the survey of (ultra−)rapid processes and their intermediates. Problems due to “hand-waving” temperature regulation/conditioning and common usage of pseudo-reference electrodes renders cryo-electrochemistry a great challenge. Herein, we describe a robust setup for performing reliable cryo-electrochemical experiments down to −80 °C. It combines highly stable but flexible temperature conditioning with gas-tight sealing of the electrochemical cell setup. Modification of a commercial palladium hydride reference electrode (PdH RE) allows for rapid temperature cycling under cryogenic conditions in aprotic organic solvents. Validation of the setup with the well-known Ferrocene|Ferrocenium (Fc|Fc⁺) redox couple gave good compliance with literature data at room temperature in a range of organic solvent-based electrolytes. Evaluation of temperature-dependent diffusion kinetic parameters, such as diffusion coefficients (D) and diffusional activation energies (E_a,D) from CVs at multiple potential scan-rates and temperature levels emphasize the reliability of the presented cryo-electrochemical setup.