Copper(II) complexes with pyridine-2,6-dicarboxylic acid from the oxidation of copper(I) iodide

Via an oxidation reaction of Cu(I) iodide with pyridine-2,6-dicarboxylic acid (H₂L) in DMF three copper(II) complexes, [(CH₃)₂NH₂]₂[CuL₂] (1), K₂[CuL₂]?H₂L?H₂O (2) and [Cu(L)(H₂O)]_n (3), were synthesized and characterized. The structures of 1–3 were determined by single crystal X-ray diffraction studies. In-situ DMF decomposition produces dimethylamine base under solvothermal conditions and a proton transfer reaction takes place for the complex formation of 1. 3-D networks are stabilized in 1 and 2 via hydrogen bonds. Complex 3 is a 1-D coordination polymer with Cu-O semi-coordination bonds. Thermal decomposition of the complexes results in the corresponding metal oxides. Also, the electrochemical behavior of 1 was determined to be a metal-centered and diffusion-controlled, one-electron reduction process.     

Kinetics of the oxidation of sulphite by tetrachloroaurate(III)

Summary The reaction between sulphite and gold(III) in hydrochloric acid medium has been studied; an initial complex is formed prior to electron transfer. The reaction rate is inversely proportional to the hydrogen ion concentration and the reaction appears to proceed through the intermediate formation of a free radical which reacts with gold(III) to give the products. Evidence for the formation of dithionate together with sulphate is presented.     

Kinetics of the oxidation of cyclohexene by thallium(III) acetate

The kinetics of the reaction by which thallium(III) acetate oxidizes cyclohexene in glacial acetic acid medium, has been studied by UV spectrophotometric observation at 30°C. The consumption of thallium(III) acetate follows a second-order rate law exhibiting first-order dependence on each of thallium(III) acetate and cyclohexene; however, the first-order dependence on cyclohexene disappears at high cyclohexene concentrations as pseudo-first-order conditions prevail above 0.2 M cyclohexene. A steady-state model of the following form is proposed: where Tl, Cy, and Com are units of Thallium(III) acetate, cyclohexene, and a reaction complex. The value of k₂ has been evaluated as 0.00027 and (k_?1 + k₂) as 0.0385k₁. For low thallium(III) acetate concentrations the reaction kinetics follow the rate law: where α = the excess concentration of cyclohexene over thallium(III) triacetate. For thallium(III) acetate concentrations above 0.02 M, double salt formation of thallium(III) acetate with product thallium(I) acetate removes thallium(III) acetate from the reaction and a modified rate law is observed. Runge–Kutta numerical solutions to the differential equations provide confirmation that the rate expressions are valid in predicting the observed concentrations of thallium(III) acetate.     

Kinetics of oxidation of phenanthrene by acidic hexacyanoferrate(III)

Under kinetically controlled conditions, phenanthrene is converted to 9-hydroxyphenanthrene by acid hexacyanoferrate(III) in 90% aqueous acetic acid. The value of –4.0 indicates that the reaction proceeds via the formation of a cation radical intermediate.

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(III) 9- 90%- . =–4,00, -.

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15^*     

Kinetics of oxidation of adonitol by manganese(III) pyrophosphate

Adonitol is oxidized to ribose by Mn(III) pyrophosphate under the conditions [adonitol] [Mn(III)]. The oxidation rate is first order with respect to both oxidatn and substrate and decreases inversly with [pyrophosphate]_free. Thermodynamic parameters are reported and a suitable mechanism involving free radicals is proposed.

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(III) [] [Mn(III)]. , - []. - .

     

Kinetics and mechanism of ruthenium(III) catalyzed oxidation of L-proline by copper(III): A free radical intervention and decarboxylation

The kinetics of ruthenium(III) catalyzed oxidation of L-proline by diperiodatocuprate(III) (DPC) in alkaline medium at constant ionic strength (0.10 mol dm⁻³) has been studied spectrophotometrically using a rapid kinetic accessory. The reaction showed first order kinetics in [DPC] and [Ru^III] and apparently less than unit order dependence each in L-proline and alkali concentrations. A mechanism involving the formation of a complex between the L-proline and the hydroxylated species of ruthenium (III) has been proposed. The active species of oxidant and catalyst were [Cu(OH)₂ (H₃IO₆)₂ (H₂IO₆)₂]⁴⁻ and [Ru (H₂O)₅OH]²⁺ respectively. The reaction constants involved in the mechanism were evaluated. The activation parameters were computed with respect to the slow step of the mechanism and discussed. The text was submitted by the authors in English.     

Reaction between copper(I)-thiourea and bismuth(III)-thiourea complexes in presence of iodide. New spot-tests for copper(II) and bismuth(III)

New and very simple spot tests are described for the detection of Bi(III), Cu(II) and I(-) ions with limits of detection of 3, 8, and 75 mug/0.05 ml respectively. Tests are also described for such combinations as Bi(III) + I(-); Bi(III) + Cu(II); and Bi(III) + Cu(II) + I(-). All the tests are based on the formation of an orange or red-orange precipitate of bismuth(III)-copper(I)-iodide-thiourea complex, for which the formula [Bi(tu)(3)I(3).Cu(tu)(3)I] (where tu = thiourea) is proposed. This complex is produced in various ways by the interaction of Bi(III), Cu(II), and I(-) ions with thiourea. Most cations and anions do not interfere, but Tl(I), Cs(I), SO(2-)(3), S(2)O(2-)(3), EDTA, and oxidizing ions such as NO(-)(2), IO(-)(3), IO(-)(4), BrO(-)(3), and MnO(-)(4) do. The complex hexakis(thioureato)sulphatomonoaquodicopper(I) [Cu(2)(tu)(6)SO(4).H(2)O] is proposed as a new spot-test reagent for Bi(III) and I(-) ions, although the sensitivity for the latter is poor.     

Kinetics and mechanism of oxidation of manganese(III) acidoporphyrin complexes with hydrogen peroxide

The reactions of manganese(III) acidotetraphenylporphyrin complexes with hydrogen peroxide in an aqueous-organic medium at 288–308 K are studied by spectrophotometry. The reaction is the oxidation of the manganese(III) complex. The spectral and kinetic data correspond to a multistep mechanism including the step of coordination of a hydrogen peroxide molecule by the central manganese atom. A possibility of formation of oxidized complexes without macrocycle destruction upon the reaction with H₂O₂ makes manganese(III) porphyrins quite promising for use as models of natural catalases.     

Kinetics of the oxidation of nitrous acid by tetrachloroaurate(III) inHCl

Summary The kinetics of the reaction between nitrous acid and gold(III) in an HCl medium was studied. The reaction was first order with respect to [Au^III] and [HNO₂]·H⁺ and Cl^- ions inhibit the rate and alkali metal ions have specific effects on the rate. The reaction appears to involve different gold(III) species, viz. AuCl _inf4 ^sup– , AuCl₃(OH₂) and AuCl₃(OH)^–, which undergo a two-equivalent reduction to gold(I) leading to the formation of NO _inf2 ^sup+ which under-goes rapid hydrolysis to give nitric acid.     

Kinetics and mechanism of the oxidation of glycolaldehyde by tetrachloroaurate(III)

The kinetics of the reaction between glycolaldehyde (GA) and tetrachloroaurate(III) in acetic acid-sodium acetate buffer has been studied. The reaction is first-order with respect to [Au^III] as well as [GA]. Both H⁺ and Cl⁻ ions retard the rate of reaction. AuCl₄⁻, AuCl₃(OH₂), and AuCl₃(OH)⁻ are the reactive species of gold(III) with gradually increasing reactivity. A reaction mechanism involving two-electron transfer rate determining steps has been proposed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 613–619, 1998     

Ethanol oxidation by imidorhenium(V) complexes: formation of amidorhenium(III) complexes

The reaction of Re(NC6H4R)Cl3(PPh3)2 (R = H, 4-Cl, 4-OMe) with 1,2-bis(diphenylphosphino)ethane (dppe) is investigated in refluxing ethanol. The reaction produces two major products, Re(NC6H4R)Cl(dppe)(2)2+ (R = H, 1-H; R = Cl, 1-Cl; R = OMe, 1-OMe) and the rhenium(III) species Re(NHC6H4R)Cl(dppe)2+ (R = H, 2-H; R = Cl, 2-Cl). Complexes 1-H (orthorhombic, Pcab, a = 22.3075(10) A, b = 23.1271(10) A, c = 23.3584(10) A, Z = 8), 1-Cl (triclinic, P1, a = 11.9403(6) A, b = 14.6673(8) A, c = 17.2664(9) A, alpha = 92.019(1) degrees, beta = 97.379(1) degrees, gamma = 90.134(1) degrees, Z = 2), and 1-OMe (triclinic, P1, a = 11.340(3) A, b = 13.134(4) A, c = 13.3796(25) A, alpha = 102.370(20) degrees, beta = 107.688(17) degrees, gamma = 114.408(20) degrees, Z = 1) are crystallographically characterized and show an average Re-N bond length (1.71 A) typical of imidorhenium(V) complexes. There is a small systematic decrease in the Re-N bond length on going from Cl to H to OMe. Complex 2-Cl (monoclinic, Cc, a = 24.2381(11) A, b = 13.4504(6) A, c = 17.466(8) A, beta = 97.06900(0) degrees, Z = 4) is also crystallographically characterized and shows a Re-N bond length (1.98 A) suggestive of amidorhenium(III). The rhenium(III) complexes exhibit unusual proton NMR spectra where all of the resonances are found at expected locations except those for the amido protons, which are at 37.8 ppm for 2-Cl and 37.3 ppm for 1-H. The phosphorus resonances are also unremarkable, but the 13C spectrum of 2-Cl shows a significantly shifted resonance at 177.3 ppm, which is assigned to the ipso carbon of the phenylamido ligand. The extraordinary shifts of the amido hydrogen and ipso carbon are attributed to second-order magnetism that is strongly focused along the axially compressed amido axis. The reducing equivalents for the formation of the Re(III) product are provided by oxidation of the ethanol solvent, which produces acetal and acetaldehyde in amounts as much as 30 equiv based on the quantity of rhenium starting material. Equal amounts of hydrogen gas are produced, suggesting that the catalyzed reaction is the dehydrogenation of ethanol to produce acetaldehyde and hydrogen gas. Metal hydrides are detected in the reaction solution, suggesting a mechanism involving beta-elimination of ethanol at the metal center. Formation of the amidorhenium(III) product possibly arises from migration of a metal hydride in the imidorhenium(V) complex.     

Kinetics of oxidation of o-dianisidine by hydrogen peroxide in the presence of antibody complexes of iron(III) coproporphyrin

The complex of iron(III) coproporphyrinl (FeCPI) with antibody D5E3 was studied as an artificial peroxidase, usingo-dianisidine as a substrate. At saturation with respect to antibody, the initial rates ofo-dianisidine oxidation are practically the same for free and bound FeCPI at a concentration 5 × 10^-9M, but the catalytic rate constant (k_c) for bound FeCPI exceed (k_c) for free FeCPI by two-to threefold. This difference can be explained by a real enhancement of (k_c) at the antibody-active site. The dependence of initial rates of the reaction on substrate concentrations obeyed Michaelis-Menten kinetics and revealed substrate activation at high concentrations ofo-dianisidine. A comparison of the Stern-Volmer constants foro-dianisidineinduced quenching of the porphyrin fluorescence proves that antibody-bound coproporphyrin is equivalently accessible to the substrate as protoporphyrin bound to apoperoxidase from horseradish peroxidase (HRP). Based on analysis of the (k_c) dependence on H₂O₂ concentrations in the FeCPI-antibody system, we suggest that interaction with hydrogen peroxide is the rate-limiting step for the oxidation reaction.     

Kinetics and mechanism of the ruthenium(III)-catalysed oxidation of aminoalcohols by alkaline hexacyanoferrate(III)

Summary The kinetics of the ruthenium(III)-catalysed oxidation of aminoalcoholsviz. 2-aminoethanol and 3-aminopropanol by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions are rapid initially, then follow a second order rate dependence with respect to each of the catalyst and the oxidant. The second order rate dependence with respect to ruthenium(III) was observed for the first time. The order in [Aminoalcohol] and [OH^–] is unity in each case. A suitable mechanism, consistent with the observed kinetic data is postulated.     

Kinetics of the Ru(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III)

The kinetics of ruthenium(III) catalyzed oxidation of formaldehyde and acetaldehyde by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The rate of oxidation of formaldehyde is directly proportional to [Fe(CN) _3– ⁶ ] while that of acetaldehyde is proportional tok[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]}, wherek, k andk are rate constants. The order of reaction in acetylaldehyde is unity while that in formaldehyde falls from 1 to 0. The rate of reaction is proportional to [Ru(III)] _T in each case. A suitable mechanism is proposed and discussed.

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Die Kinetik der Ru(III)-katalysierten Oxidation von Formaldehyd und Acetaldehyd mittels alkalischem Hexacyanoferrat(III)

Zusammenfassung Die Untersuchung der Kinetik erfolgte spektrophotometrisch. Die Geschwindigkeitskonstante der Oxidation von Formaldehyd ist direkt proportional zu [Fe(CN) _3– ⁶ ], währenddessen die entsprechende Konstante für Acetaldehyd proportional zuk[Fe(CN) _3– ⁶ ]/{k +k[Fe(CN) _3– ⁶ ]} ist, wobeik,k undk Geschwindigkeitskonstanten sind. Die Reaktionsordnung für Acetaldehyd ist eine erste, die für Formaldehyd fällt von erster bis zu nullter Ordnung. Die Geschwindigkeitskonstante ist in jedem Fall proportional zu [Ru(III)] _T . Es wird ein passender Mechanismus vorgeschlagen.

     

Kinetics and mechanism of the oxidation of iodide by diaquote- trakis(2,2′-bipyridine)-μ-oxodiruthenium(III) ion in acid medium

Transition Metal Chemistry - The kinetics of the oxidation of iodide by diaquotetrakis-(2,2-bipyridine)-μ-oxodiruthenium(III), [Ru2O]4+, were studied in aqueous perchloric acid at...     

Kinetics of oxidation of iodide by hexacyanoferrate(II) in binary aqueous solvent mixtures

Summary The kinetics of the oxidation of iodide by hexacyanoferrate(III) have been studied in different H₂O-methanol, t-butanol, ethylene glycol glycerol, glucose or sucrose mixtures. Specific solvent effects are found as shown by the different trends in activation parameters and in the variations of the initial state and transition state chemical potentials as observed in different media. From the results of a multiple linear correlation, it is concluded that the kinetics are controlled by the ionizing power of the solvents, their relaxation times and the outer sphere reorganization energies.     

Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processes

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by ¹H NMR spectroscopy. Under the experimental conditions, AuCl and AuCl₃(OH)^? are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H⁺ and Cl^? on the second‐order rate constant k₂′ have been analyzed, and accordingly the rate law has been deduced: k₂′ = (k₁[H⁺][Cl^?] + k₃K₄K₅)/(K₄K₅ + [H⁺][Cl^?]). Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 473–482, 2009     

Oxidation of iodide by a series of Fe(III) complexes in acetonitrile

The oxidations of iodide by [Fe(III)(bpy)2(CN)2]NO3, [Fe(III)(dmbpy)2(CN)2]NO3, [Fe(III)(CH3Cp)2]PF6, and [Fe(III)(5-Cl-phen)2(CN)2]NO3 at 25 degrees C, ionic strength of 0.10 M in acetonitrile, are catalyzed by trace levels of copper ions. This copper catalysis can be effectively masked with the addition of 5.0 mM 2,2'-bipyridine (bpy), which permits the rate law of the direct reactions to be determined: -d[Fe(III)]/dt = 2(k1[I-] + k2[I-]2)[Fe(III)]. According to 1H NMR and UV-vis spectra, the products of the reaction are I3- and the corresponding Fe(II) complexes, with the stoichiometric ratio (delta[I3-]/delta[Fe(II)]) of 1:2. Linear free-energy relationships (LFERs) are obtained for both log k1 and log k2 vs E(1/2) with slopes of 16.1 and 13.3 V(-1), respectively. A mechanism is inferred in which k1 corresponds to simple electron transfer to form I* plus Fe(II), while k2 leads directly to I2(-*). From the mild kinetic inhibition of the k1 path by [Fe(II)(bpy)2(CN)2] the standard potential (Eo) of I*/I- is derived: Eo = 0.60 +/- 0.01 V (vs [Fe(Cp)2](+/0)).