Mutual Influence of Electrode Processes during Electrodeposition of Layered Structures by the Single-Bath Method: The Effect of Nickel Deposition and Hydrogen Evolution on the Transport of Copper Ions in Acetate and Sulfamate Electrolytes

The effect of nickel deposition and hydrogen evolution on the transport of copper-containing ions is studied by numerically solving an electrodiffusion problem with use made of variational values of the formation constants of nickel and copper complexes in acetate and sulfamate electrolytes and thicknesses of the diffusion layer. It is concluded that the major contribution to the mass transfer is made by the effects of exaltation of the migration current and by the agitation of the near-electrode layer of electrolyte by evolving hydrogen. The possibility of employing migration effects in order to reduce the limiting current of copper in the region of nickel deposition and hydrogen evolution is substantiated. This will decrease the copper content in a layer of alloy during electrodeposition of layered structures.     

Synthesis and crystal structure of trans-tetrachloro(C, C-dichloro-C-phenyl-methyl-nitrido)(phenylnitrilo)tungsten(VI), trans-[WCl4(NCCl2Ph)(NCPh)]

A product of the insertion, namely, trans-tetrachloro(C, C-dichloro-C-phenyl-methyl-nitrido)(phenylnitrilo) tungsten(VI), trans-[WCl₄(NCCl₂ Ph)(NCPh)] (I), is synthesized by the reaction of WCl₆ with PhCN in CCl₄ under refluxing for 2 h. Judging from the characteristic IR bands ν(C≡N) and ν(W≡N), the complex synthesized is identical to the compound prepared earlier at room temperature. The crystal structure of complex I is determined using X-ray diffraction analysis. It is revealed for the first time that the coordination polyhedron of the tungsten atom in complex I is a distorted octahedron with four chlorine atoms in the equatorial plane. The axial positions are occupied by the N(1) atom [W-N(1), 2.265(13) Å] of the coordinated benzonitrile group and the N(2) atom [W-N(2), 1.732(13) Å] of the multiply bonded ligand NCCl₂ Ph. __________ Translated from Kristallografiya, Vol. 49, No. 4, 2004, pp. 728–731. Original Russian Text Copyright ? 2004 by Sinyakov, Aleksandrov, Ovchinnikova.     

Gold distribution in pyrrhotite crystals grown under hydrothermal conditions

The distribution of gold between pyrrhotite and greenockite was studied by the method of hydrothermal thermal-gradient cocrystallization of the components at a temperature of 450°C, a pressure of 1 kbar, and different activities of sulfur in the presence of As and Se impurities. The structural component of Au impurity in these minerals was selected by studying statistical samplings of the analytical data for single crystals. Ferrous greenockite incorporates a maximum of 10 ± 2 ppm Au in solid solution. The incorporation limit of Au in stoichiometric pyrrhotite was estimated to be 25 ± 9 ppm; for nonstoichiometric pyrrhotites, it is lower. The As and Se impurities barely affect the concentration of structural gold in the minerals. It was shown that constitutional vacancies in pyrrhotite do not capture Au impurity. The observed phenomenon may be the growth effect related to the surface properties of nonstoichiometric pyrrhotite crystals grown under hydrothermal conditions. Differences in the surface structure of pyrrhotites of different composition and the products of their sorption of gold were revealed by X-ray photoelectron spectroscopy.     

Mutual Influence of Electrode Processes during Electrodeposition of Layered Structures by a Single-Bath Method: Effect of Nickel Deposition and Hydrogen Evolution on the Mass Transfer of Copper in a Sulfosalicylate Electrolyte

The work justifies the selection of a sulfosalicylate copper–nickel electrolyte and its composition for obtaining nanostructures comprising alternate magnetic and nonmagnetic layers by a single-bath method. According to calculations of an equilibrium composition of the electrolyte and electrodiffusion fluxes of discharging species, in a neutral region of pH copper exists in the form of multicharged anions CuSSA^3–, and the migration effects must reduce the rate of the mass transfer of copper-containing species with increasing current of the parallel reaction of discharge of nickel ions. Dependences of the partial current density of copper deposition on the electrode potential are studied at various values of pH of the copper and copper–nickel electrolytes. Experimental results are analyzed on the basis of modeling concepts. It is shown that the drop of the partial current density of copper deposition below its limiting value at potentials of deposition of a magnetic layer is connected with the emergence of migration effects.     

Copper in Acid Chloride Solutions: Electrochemical Behavior by Quartz Microgravimetry and Voltammetry

The cathodic deposition of copper on a gold electrode and its subsequent anodic dissolution in an acid chloride solution, where two successive stages of a one-electron transfer are distinguishable because of the stability of chloride complexes of Cu(I), is studied by voltammetry and quartz microgravimetry. The formation of a film of an intermediate compound of Cu(I) during the deposition and dissolution of copper is revealed experimentally. Techniques for identifying the intermediate solid species are suggested. During a cathodic polarization, a film of intermediate compound CuCl forms at a reduced concentration of chloride ions in the Cu(II)/Cu(I) process, while during the anodic dissolution of the copper deposit formed during the cathodic polarization the intermediates appear in the Cu(0)/Cu(I) process, the concentration of chloride ions notwithstanding. The change in the electrochemical behavior of the system caused by a decrease in the concentration of chloride ions is explained.     

Sonochemical synthesis of Biginelli compounds

The ultrasound effect accelerates the Biginelli reaction 40 and more times. A sonochemical method for the synthesis of ethyl 4-R-6-methyl-2-oxo- and 4-R-6-methyl-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates was developed. The target products were obtained within 2 to 5 min in 90—95% yields.     

Complex Formation During Molybdenum Chlorination in DMF Medium

IR and EPR studies of solutions formed after molybdenum chlorination in the medium of DMF revealed the diamagnetic Mo(VI) and paramagnetic Mo(V) complexes of composition R₂[MoOCl₅], where R is [(CH₃)₂NCOH₂]⁺ (I) and [(CH₃)₂NH₂]⁺ (II). The hydrolysis of complex II was found to give dimethyl-substituted ammonium chloride.     

Transformations of pyridine bases on a nickel-aluminum catalyst

The electronic structures of some pyridine bases are analyzed by means of ¹H and ¹³C NMR spectroscopic data for substituted pyridines and the calculated bond orders in the pyridine ring. The differences in the chemical bonds in the pyridine ring of isomeric methylpyridines and the carbon—carbon bonds between the ring and the methyl groups in these compounds are in agreement with the experimental data on the thermal stability of the simplest pyridine bases and the gas-phase transformation of the isomeric methylpyridines on an industrial nickel—aluminum catalyst. The possibility of obtaining mono- or dialkylpyridines under these conditions, depending on the structure of the starting pyridine bases, is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 371–374, March, 1982.     

The globulins of cotton seeds XI. The structure of the chymotryptic peptides of the 7S globulin

Summary The amino-acid sequences of the chymotryptic peptides of the 7S globulin of cotton seeds have been determined.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 682–687, September–October, 1977.