A Concise Copper-Catalyzed Oxytrifluoromethylation of Allyl Alcohols

An efficient oxytrifluoromethylation of allyl alcohols has been developed using Togni’s reagent II as a trifluoromethylation reagent and cuprous chloride as a catalyst. This reaction proceeded through a one-pot process of trifluoromethylation followed by nucleophilic attack of the vicinal hydroxyl group. This strategy features good diastereoselectivity and broad substrate scope, which provides a facile access to various α-CF3-substituted epoxides.

Effect of cations on the removal rate of chloride ions and mechanism analysis in high-salt wastewater

Precipitation dechlorination has the advantage of being a simple process with a low cost. However, there are few reports on the effect of cations on dechlorination. In this study, we investigated the effect of cations in high-salt wastewater on the removal of chlorine ions by cuprous chloride precipitation and analysed the corresponding mechanism. A series of investigations revealed that Fe3+ could oxidise sulphite, thereby reducing the removal rate of chlorine ions. The reaction between magnesium and sulphite results in precipitation, which has a slightly adverse effect on the removal of chloride ions. Hexavalent chromium oxidises the chloride ion, resulting in the formation of chlorine gas, which improves the removal rate. Ferrous and manganese, however, do not have a notable effect on chlorine removal.

Estimation of the Generation Rate of H· Radicals in a Megasonic Field Using an Electrochemical Technique

Radical formation and detection in aqueous solutions under acoustic irradiation are important during wet cleaning processes in semiconductor industries. Oxidizing radicals such as hydroxyl and hydroperoxyl radicals have been widely studied and characterized using fluorescence and chemiluminescence methods. Hydrogen radicals, which are strongly reducing in nature, have not received much attention. In this study, the rate of hydrogen radical generation in a megasonic field (0.93 MHz) was measured using an electrochemical technique. Specifically, the method is based on the reduction of cupric ions to cuprous chloride complex by the hydrogen radicals in the presence of an excess of chloride ions. This is followed by chronoamperometric determination of the oxidation of cuprous chloride complex back to cupric ions. Hydrogen radical generation rate was measured at different megasonic power densities.

Complementary methods for characterization of the corrosion products on the surface of Ag60Cu26Zn14 and Ag58.5Cu31.5Pd10 brazing alloys

Corrosion products formed on the surface of two silver brazing alloys after the potentiostatic polarization in 3.5% sodium chloride solution were characterized by the standard methods such as, the X-ray diffraction, micro-Raman spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy. This paper presents the results of a laser desorption/ionization mass spectrometry (LDI MS) analysis as a new approach to the characterization of corrosion products. The potential of the anodic polarization was 0.5 V versus saturated calomel electrode, and the process duration was 300 s. The corrosion layers on both investigated alloys were similar in composition with cuprous chloride and silver chloride as the main components and had strong indications of cuprous oxide formation. The major difference between these two layers was the existence of zinc hydroxychloride as the corrosion product of Ag-Cu-Zn alloy. Palladium compounds were not found in the case of Ag-Cu-Pd alloy. The results of different methods have shown a good consistency. Complementarity between the used methods was useful in the interpretation of the results for each used method. This study has demonstrated that LDI MS can be used as an efficient additional method together with the traditional ones.

Electrochemical recovery of tellurium from metallurgical industrial waste

The current study outlines the electrochemical recovery of tellurium from a metallurgical plant waste fraction, namely Doré slag. In the precious metals plant, tellurium is enriched to the TROF (Tilting, Rotating Oxy Fuel) furnace slag and is therefore considered to be a lost resource—although the slag itself still contains a recoverable amount of tellurium. To recover Te, the slag is first leached in aqua regia, to produce multimetal pregnant leach solution (PLS) with 421 ppm of Te and dominating dissolved elements Na, Ba, Bi, Cu, As, B, Fe and Pb (in the range of 1.4–6.4 g dm−3), as well as trace elements at the ppb to ppm scale. The exposure of slag to chloride-rich solution enables the formation of cuprous chloride complex and consequently, a decrease in the reduction potential of elemental copper. This allows improved selectivity in electrochemical recovery of Te. The results suggest that electrowinning (EW) is a preferred Te recovery method at concentrations above 300 ppm, whereas at lower concentrations EDRR is favoured. The purity of recovered tellurium is investigated with SEM–EDS (scanning electron microscope–energy dispersion spectroscopy). Based on the study, a new, combined two-stage electrochemical recovery process of tellurium from Doré slag PLS is proposed: EW followed by EDRR. Graphic abstract

Synthesis of 1,1′-Bis(1-Methyl/Chloro-2,3,4,5-Tetraphenyl-1-Silacyclopentadienyl) [Ph4C4Si(Me/Cl)-(Me/Cl)SiC4Ph4] from Silole Anion [MeSiC4Ph4]−•[Li+ or Na+] and Silole Dianion [SiC4Ph4]2−•2[Li+]; Oxidative Coupling of Silole Anion [MeSiC4Ph4]−•[Li+ or Na+] by Ferrous Chloride (FeCl2) and Oxidative Coupling and Chlorination of Silole Dianion [SiC4Ph4]2−•2[Li+] by Cupric Chloride (CuCl2)

A reaction of silole anion {[MeSiC4Ph4]−•[Li+ or Na+] (1) with anhydrous ferrous chloride (FeCl2) in THF (tetrahydrofuran) gives 1,1′-bis(1-methyl-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Me)-(Me)SiC4Ph4] (2) with precipitation of iron metal in high yield. Silole dianion {[SiC4Ph4]2−•2[Li+] (3) is added to anhydrous cupric chloride (CuCl2) in THF at −78 °C, then the dark red solution changes into a greenish solution. From the solution, a green solid is isolated, and stirring it in toluene at room temperature provides quantitatively 1,1′-bis(1-chloro-2,3,4,5-tetraphenyl-1-silacyclopentadienyl) [Ph4C4Si(Cl)-(Cl)SiC4Ph4] (4) with precipitation of copper metal in toluene. The green solid is suggested to be 1,1′-bissilolyl bisradical [Ph4C4Si-SiC4Ph4]2• (8), and lithium cuprous chloride salts {[Li2CuICl2]+•[CuICl2]−}. Both reactions are initiated by single-electron transfer (SET) from the electron-rich anionic silole substrates (1 and 3) to iron(II) and copper(II).

Comparative Analysis of Crystal Structures between 2,2′-Bipyridine and 6,6′-Dimethyl-2,2′-Bipyridine Supported CuSCF3 Complexes: An Unusual Coordination Transition from Mononuclear to Binuclear Mode

We report herein the synthesis of CuSCF3 complex supported by 6,6′-dimethyl-2,2′-bipyridine via the strategy of triphenylphosphine-mediated deoxygenation of CF3SO2Na in the presence of cuprous chloride. The molecular structure of this new cuprous complex was characterized by elemental analysis, 1H (13C, 19F) NMR spectra and verified by X-ray crystallography. Unlike the classical [(2,2′- bipyridine)Cu(SCF3)] complex, 6,6′-dimethyl-2,2′-bipyridine supported cuprous trifluoromethylthiolate complex was dimerized in the form of [{(6,6′-dimethyl-2,2′-bipyridine)Cu(SCF3)}2]. The X-ray crystal structure revealed the Cu2S2 cyclic pattern and sulfur atoms serving as the bridge. The Cu-Cu distance was equal to 3.083 Å which was remarkably longer than the analogous [{(1,10-phenanthroline)Cu(SCF3)}2] (2.5781(9) Å). This interesting phenomenon demonstrated that the substituents on the ligand scaffolds have profound influence on the coordination modes of these N,N-ligand coordinated CuSCF3 complexes.

In-Situ Raman Characterization of Initial Corrosion Behavior of Copper in Neutral 3.5% (wt.) NaCl Solution

In order to investigate the role of chloride ion in the corrosion film formation of copper and its evolution over time, the initial corrosion behavior of copper in neutral 3.5% (wt.) NaCl solution was characterized by in-situ Raman spectroscopy along with electrochemical tests. The results demonstrated that the cuprous chloride complexes, such as CuCl and CuCl 2 − were produced through electrode processes, while the cuprite, Cu 2 O seemed to be formed via the chemical precipitation reaction instead of a direct electrochemical transformation from the metal matrix or CuCl and it occurred rather slowly. At the open circuit potential, the chlorides were generated first in the initial 2 h and then they transformed to the oxides with the CuCl 2 − content in the interface increasing. The in-situ Raman characterization directly evidenced the previously reported mechanism of growth of oxide layers on copper surfaces in neutral Cl − media and clearly showed the formation of a corrosion product film and its evolution over time. The electrochemical tests corresponded to the results of in-situ Raman characterization well.