Synergism in the Activity of the Mixed Oligoallene Complexes of Palladium and Group VIII Nonnoble Metals in the Hydrogenation of Dienes to Alkenes

The superadditivity of the catalytic properties of various bimetallic Pd–Ni, Pd–Co, and Pd–Fe complexes with oligodimethylallene ligands was studied. Palladium–nickel catalysts of an equimolar composition exhibited the highest activity. The complexes were studied by IR spectroscopy. Conceivable structures were proposed for the complexes. The main kinetic features of the isoprene hydrogenation reaction under the action of palladium and palladium–nickel systems were studied. A two-center mechanism, which takes into account the presence of properly arranged palladium and nickel atoms in the active center of the catalyst, was considered as a probable reason for the appearance of a synergistic effect.     

Reaction kinetics in replacement of zinc ions by copper ions in complexes with cyclic and noncyclic tetramines

A kinetic study has been made of reactions of zinc ion replacement by copper in complexes with macrocyclic and noncyclic tetramines. The activation parameters of these processes have been determined, and reaction mechanisms are proposed. A kinetic macrocyclic effect has been found in reactions of central atom replacement in tetraazamacrocyclic complexes of zinc.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 2, pp. 175–182, March–April, 1985.     

Platinum(IV) complexes of reducing sugars in an alkaline medium and their resistance to reaction with N-bromosuccinimide. A kinetic study

Spectrophotometric studies support the formation of { Pt^IV–S} (where S = glucose, galactose and fructose) complexes in an alkaline medium. The resistance of these complexes to reaction with N-bromosuccinimide (NBS) has been observed. The kinetic data also support the formation of { Pt^IV –S} complexes.     

Mechanism of transannular bromination reactions of diolefins of the bicyclo[3.3.1]nonane series

Mechanisms of reactions of brominated diolefins of the bicyclo[3.3.1]nonane series were studied. The reaction of transannular cyclization into adamantane derivatives proceeds by a molecular-ionic mechanism, and the rate of reaction obeys a third-order kinetic equation. An analysis of the calculated thermodynamic parameters of the transition state shows that intermediate complexes with charge transfer of the diolefin...Br₂ and diolefin...Br₄ type are formed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 52–56, January–February, 1985.     

Study of kinetics and mechanism of sulfonation of thiophene and its derivatives by complex compounds of sulfuric anhydride

By quantitatively studying the sulfonation of thiophene and its homologs by complexes of sulfuric anhydride with ethers, amides, and trialkyl phosphates it was possible to determine kinetic and thermodynamic parameters of the process, to propose a S_E2 type reaction mechanism and also to reveal a quantitative dependence of the rate constant of the sulfonation reaction of thiophene on the basicity of the complex-forming agent: The sulfonating activity of the complexes studied increases in the series — amides < trialkyl phosphates < ethers, which is the reverse of the increase in the basicity series of a donor.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 34–39, January, 1986.     

Anodisation of copper in thiourea- and formamidine disulphide-containing acid solution.: Part I. Identification of products and reaction pathway

The anodic behaviour of copper in aqueous 0.5 M sulphuric acid containing different amounts of dissolved thiourea or formamidine disulphide was investigated at 298 K, combining data from electrochemical polarisation, chemical analysis, UV–vis spectroscopy, XPS and EDAX analysis, and structural information on copper–thiourea complexes. The main reactions depend on the applied potential and initial thiourea concentration. In the potential range −0.30≤E≤0.075 V (versus SCE), the electro-oxidation of thiourea to formamidine disulphide, the formation of Cu(I)–thiourea soluble complexes, and Cu(I)–thiourea complex polymer-like films, are the most relevant processes. The formation of this film depends on certain critical thiourea/copper ion molar concentration ratios at the reaction interface. At low positive potentials, the former reaction is under intermediate kinetic control, with the diffusion of thiourea from the solution playing a key role. For E≥0.075 V, soluble Cu(II) ions in the solution are formed and the anodic film is gradually changed to another one consisting of copper sulphide and residual copper. The new film assists the localised electrodissolution of copper. A complex reaction pathway for copper anodisation in these media for the low and high potential range is advanced.     

Investigations of Cobalt, Nickel, and Copper Diethyldithiocarbamates Using Thermal Lens Spectrometry

Thermal lens spectrometry was used to study the dissociation kinetics of diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II) as a function of pH in the presence of chloride and sulfate ions. It is shown that, as distinct from conventional spectrophotometric and potentiometric measurements, the reversible dissociation of the test complexes and the irreversible oxidation of the ligand can be studied separately (at a level of n × 10^–8–n × 10^–6 M) using thermal lens spectrometry. Because of work in more dilute solutions and due account of the kinetic features of the systems in question, thermal lens spectrometry provides a higher accuracy of the determination of stability constants for diethyldithiocarbamate complexes of copper(II), cobalt(III), and nickel(II). The adsorption of the diethyldithiocarbamate complexes in question from water–ethanol solutions (1 : 3) on Silasorb C₁₈ silica is studied, and the adsorption constants are determined. The limits of detection of copper(II), cobalt(III), and nickel(II) diethyldithiocarbamates obtained in extraction–thermal-lens determination are n × 10^–8 M.     

Kinetics of methanation of carbon dioxide on a nickel catalyst

The kinetics of hydrogenation of CO₂ to methane on an NKM-4A nickel-containing catalyst was studied in a wide range of change of partial pressures of hydrogen and carbon dioxide at 498–543 K. It was shown that when hydrogen is replaced by deuterium in the reaction, a reverse kinetic isotope effect is observed. The kinetic equation of the reaction was derived and a stepwise scheme is proposed which includes the involvement of oxygen-containing intermediates in the process without preliminary dissociation of CO₂.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 26, No. 5, pp. 620–624, September–October, 1990.     

Kinetics of Direct Reduction of Chrome Iron Ore

The kinetics of direct reduction of artificial chrome iron ore was studied by isothermal and non-isothermal methods. In the initial, middle and final periods, the reaction is controlled by nucleation and growth, a phase boundary reaction, and diffusion, respectively. In the main reaction region, the kinetic equation is 1–(1–)^1/3=kt and the apparent activation energy is 270 kJ mol^–1. The kinetic mechanisms found with the isothermal and non-isothermal methods do not differ, and the activation energy values are approximately the same. However, the non-isothermal method can demonstrate the kinetic process completely.This revised version was published online in November 2005 with corrections to the Cover Date.     

Nitriding of titanium with plasma jet under reduced pressure

The nitriding of titanium with argon-nitrogen (3%) and argon-nitrogen (3%)-hydrogen (2%) plasma jets at pressures of 190 torr was studied. The reaction kinetics obeyed mainly a parabolic law. The parabolic kinetic constants were 10^–10–10^–8 g² cm^–4 s^–1, which were 2–3 orders of magnitude larger than those in R.F. discharges. From emission spectroscopy, nitrogen atoms in the excited states were observed. The nitrogen atoms can promote the nitriding reaction. The effect of the addition of hydrogen to nitrogen is also briefly discussed.     

Kinetic Aspects of Dimethylamine Hydroxyethylation in the Presence of Water

The kinetics of dimethylamine hydroxyethylation at an ethylene oxide : dimethylamine : water molar ratio of 1 : 3 : (0.1–0.5) was studied in the temperature range 20–50°C. A kinetic model of the reaction, which adequately describes the experimental data, was suggested.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 4, 2005, pp. 687–689.Original Russian Text Copyright © 2005 by Danov, Kolesnikov, Efremov, Mezhenin.     

Ruthenium and enzyme-catalyzed dynamic kinetic resolution of alcohols

Ruthenium acts as a good catalyst for the racemization reaction of secondary alcohols and amines. Ruthenium-catalyzed racemization is coupled with enzymatic kinetic resolution to prepare chiral compounds in 100% theoretical yield. Ten ruthenium complexes (1–10) act as a good catalyst the for racemization reaction and are also compatible with DKR process. Two other ruthenium complexes [RuCl₂(PPh₃)₃] and [Cp^*RuCl(COD)] are active for racemization reaction but their successful compatibility with DKR has not yet been reported. Ru/γ-Al₂O₃ and Ru–HAP are the heterogeneous catalysts used for the racemization reaction. They have also not been employed for DKR process. Polymer supported ruthenium is employed as a reusable racemization catalyst for aerobic DKR of alcohols.     

Kinetics of hydrogenation of cyclododeca-3,7-diene-1-one on supported metal catalysts

The kinetics of hydrogenation of cyclododeca-3,7-diene-1-one on commercially available supported metal catalysts has been studied in ethyl alcohol solutions at 323–363 K and 0.1–2.5 MP a pressure of hydrogen. The experimental data have been related to kinetic equations of the Langmuir-Hinshelwood type. The reaction schemes which best fit the experimental data are shown.     

Induced decomposition of acetylcyclohexylsulfonyl peroxide

The kinetics of thermal decomposition of acetylcyclohexylsulfonyl peroxide is studied in an-decane solution in an oxygen atmosphere (303–333 K) and under anaerobic conditions (313–333 K); the reaction products are also studied in a cyclohexane solution under oxygenfree conditions (323 K). In the absence of oxygen, the reaction is found to proceedvia a chain-radical mechanism. Some kinetic parameters of the process are determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1049–1052, June, 1995.This work was supported by the Russian Foundation for Basic Research (Project No. 93-03-5231).     

Oxidative Carbonylation of Alkynes in an Oscillation Mode: I. Concentration Limits for Oscillations in the Course of Phenylacetylene Carbonylation and Possible Mechanisms of the Process

An oscillating reaction of alkyne oxidative carbonylation is studied in a PdI₂–KI–CH₃OH catalytic system. Concentration limits for oscillations are found. A tentative kinetic model for the process is proposed. The mechanism of oscillations is discussed.     

Studies on intermolecular interactions of metal chelate complexes. Part X. Interactions of metal chelates with ozone

Summary The interactions of more than forty metal chelate complexes, dithiocarbamates, dithiophosphates and acetylacetonates, with ozone are studied in homogeneous phase and the stoichiometry and the rate constants of the reactions estimated. Most powerful ozone deactivators are nickel(II) and copper(II) dithiocarbamate and dithiophosphate complexes interacting with 6.5 moles ozone per mole of the ligand with rate constant >0⁶m · I^–1 · s^–1. The remote ligand substituents do not influence the reaction parameters. Other sulphur-containing complexes of iron(III), cobalt(II), cobalt(III), zinc(II), manganese(III), bismuth(III), antimony(III), arsenic(III), cadmium(II), platinum(II), palladium(II) and chromium(III) deactivate 3–4 moles ozone per mole ligand with rate constants of 10²–10⁴ m · I^–1 · s^–1. Acetylacetonate complexes of copper(II), nickel(II), cobalt(III), iron(III), chromium (III), and oxovanadium(II) deactivate 1–3 moles ozone per mole ligand with a rate constant of 10–10⁴ m · I^–1 · s^–1. Using e.p.r. and electronic spectra, some intermediate products are detected and the mechanism of the reaction is discussed. The reported data are compared with other widely used antiozonants and the metal chelates are shown to have several advantages.     

Oxidation of tetraaza macrocyclic complexes of nickel(II) with peroxobisulfate ions

Spectrophotometry has been used to study the kinetics of oxidation of some tetraaza macrocyclic complexes of nickel (II) with peroxobisulfate ions in perchloric and sulfuric acid solutions. A scheme of the processes taking place has been proposed and the activation parameters of the reactions determined. The influence of different factors (pH value, ionic strength of the solution, temperature) on the kinetic parameters of the oxidation reactions has been studied. A significant influence of the conformations of the macrocyclic ligands in the complexes on the rate of the processes has been noticed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 5, pp. 577–583, September–October, 1988.     

Kinetic Study of Catalytic Hydrogenation of Thiophene on a Palladium Sulfide Catalyst

The kinetics of thiophene hydrogenation on a palladium sulfide catalyst is studied at high hydrogen pressures. The reaction mainly occurs via the consecutive scheme: the reaction of thiophene with hydrogen results in the formation of tetrahydrothiophene, which partially decomposes under the action of hydrogen to yield butane and hydrogen sulfide. A kinetic model describing the reaction rates and the selectivity to tetrahydrothiophene at 0.2–3.0 MPa and 493–533 K is proposed. The rate constants and activation energies are determined. The effect of temperature and pressure on the maximal yield of tetrahydrothiophene is examined.     

Acid–Base Complexes of Tetrahalogentetraazaporphyrins with tert-Butylamine and Tributylamine in Benzene: Synthesis and Stability

Kinetics of formation of acid–base tetrachloro- and tetrabromotetraazaporphyrin complexes with tert-butylamine and tributylamine in benzene was studied. The rate and activation parameters of the process were shown to depend on the nature of protolytes. The mechanism of intermolecular proton transfer from NH groups of tetrahalogentetraazaporphyrins to the nitrogen-containing base is proposed. The structures of acid–base complexes are considered and their kinetic stability is studied.     

Acid and Complexing Properties of Tetraazaporphyrins

In this review, the kinetic regularities underlying the formation and stability of acid–base tetraazaporphyrin complexes with nitrogen bases in benzene (chlorobenzene) are considered. The relationships between the structure of protolytes and their reactivities are discussed. The role of the acid–base interactions in the reaction of magnesium acetate or acetylacetonate with tetrahalogen- and octaphenyl-substituted tetraazaporphyrins in the nitrogen-containing base–benzene system was revealed. The possible mechanisms of the processes under study are considered and a relatioship is established between the reaction rate constants and structural changes in a solution.