Methionine anation of aquachromium(III)

The kinetics of anation of chromium(III) species, [Cr(H₂O)₆]³⁺ and [Cr(H₂O)₅OH]²⁺, by DL-methionine have been studied spectrophotometrically. Effects of varying [methionine]_T, [H⁺], and temperature were investigated. The results are in accord with a mechanism involving a fast 11 outer-sphere association between chromium(III) species and amino acid zwitterion, followed by transformation of the outer-into inner-sphere complex by slow interchange. The rate law consistent with the mechanism is as follows:

Kinetics and mechanism of oxidation of chromium(III)-tetraoxalylurea complex by periodate

A novel chromium(III) complex of tetraoxalylurea was prepared. In aqueous solutions, [Cr^III(H₂L)(H₂O)]⁺ (H₂L = diprotonated tetraoxalylurea) is oxidized by IO ₄ ^– according to the rate law

Kinetic study of hydrogen peroxide reaction with hydroxonitrilotri(methylenephosphonato)iron(III) complex

The decomposition of hydrogen peroxide in the presence of hydroxonitrilotri(methylenephosphonato)iron(III), [Fe(NTMP)(OH)^4–], was studied in nitrate media (=0.10–0.26 M) over the 0.2–0.5 mM concentration range for the iron complex and the temperature range 26–40°C. The rate law;

Oxidation of chromium(III) by alkaline hexacyanoferrate(III)

Alkaline hexacyanoferrate(III) oxidation of freshly prepared solutions of Cr^III (pH>12) at 27°C follows the rate law, Equation 1:

Kinetics of the manganese(III)-oxalate reaction in acidic sulphate media

The kinetics of the reaction of manganese(III) with oxalic acid (OA) has been studied in H₂SO₄ solutions. Under the experimental conditions of 6 × 10^–3 <>₀ < 0.4=" mol=">^–3 and [H₂SO₄]₀ 0.2 mol dm^–3 the observed pseudo-first order rate constant k _obs follows the expression

Kinetics of substitution of aquo ligands fromcis-diaquo-bis-(biguanide) cobalt(III) and chromium(III) ions by aspartic acid in ethanol—water mixtures

The kinetics of substitution of aqua ligands fromcis-diaqua-bis(biguanide)cobalt(III) and chromium(III) ions by aspartic acid in EtOH–H₂O media have been studied spectrophotometrically in the 30 to 45°C range. We propose the following rate law for the anation

Kinetic studies of the oxidation ofN-(2-hydroxycyclohexyl)-ethylenediaminetriacetatochromate(III) by periodate

The kinetics of the oxidation of [Cr^III(H₂O)(XOH)], (XOH=N-(2-hydroxycyclohexyl)ethylenediaminetriacetate) to Cr^VI by periodate have been investigated in aqueous solution at various pH values (6.00–7.20) and temperatures (15.0–35.0°C). The reaction follows the rate law:

Surface Mediated Organometallic Synthesis: Formation of [H5Os10(CO)24]− by Hydrogenation of Silica-Supported [Os(CO)3(OH)2]n as a Springboard for a High-Yield Synthesis of [H4Os10(CO)24]2− Starting from α-[Os(CO)3Cl2]2 and Working in Ethylene Glycol Solution

New high yield routes to the high nuclearity hydrido carbonyl clusters [H₅Os₁₀(CO)₂₄]^- and [H₄Os₁₀(CO)₂₄]^2-, model systems for the chemisorption of CO and H₂ on metal surfaces, are reported. [H₅Os₁₀(CO)₂₄]^- is obtained in good yields by hydrogenation (1 atm) at 200°C of physisorbed [Os(CO)₃(OH)₂]_n whereas in refluxing ethylene glycol solution, that is less acidic than the silica surface, [H₄Os₁₀(CO)₂₄]^2- is obtained in high yield starting from [Os(CO)₃(OH)₂]_n or, more conveniently, from -[Os(CO)₃Cl₂]₂ in the presence of the stoichiometric amount of sodium carbonate. The quantitative equilibrium

Solubility of Siderite (FeCO3) in NaCl Solutions

The solubility of siderite (FeCO₃) at 25°C under constant CO₂ partial pressure [p(CO₂)] was determined in NaCl solutions as a function of ionic strength. The dissolution of FeCO₃(s) for the reaction

Substitution of aqua ligands fromcis-diaqua-bis(bipyridyl) ruthenium(II) by 1, 10-phenanthroline in aqueous medium

The kinetics of aqua ligand substitution fromcis-[Ru(bipy)₂(H₂O)₂]²⁺ by 1, 10-phenanthroline (phen) have been studied spectrophotometrically in the 35 to 50°C temperature range. We propose the following rate law for the reaction within the 3.65 to 5.5 pH range:

Kinetics and mechanism of anation of hexaaquochromium(III) by 2-aminopyridine

The kinetics of substitution of aqua ligands from the hexaaquochromium(III) ion by 2-aminopyridine (2-ampyH⁺) in aqueous medium has been studied spectrophotometrically in the 40–55° C range. The rate law involving the outer sphere complex formation has been established at pH 2.7 as

Studies on mixed ligand complexes of cobalt(II), nickel(II), copper(II) and zinc(II) involving 8-hydroxyquinoline-5-sulphonic acid as a primary ligand and substituted catechols as secondary ligands

Summary Stability constants (K _MAL ^MA ) and other thermodynamic parameters of the MAL complexes (charges omitted) [M=Co^II, Ni^II, Cu^II or Zn^II; AH₂=8-hydroxyquinoline-5-sulphonic acid; LH₂=catechol (L¹H₂), 1,2-dihydroxybenzene-sulphonate (L²H₂), 1,2-dihydroxybenzene-3, 5-disulphonate (L³H₂), 4-nitro-1,2-dihydroxybenzene (L⁴H₂)] have been determined at 25°C and at an 0.1 M KNO₃ ionic strength by the extended Irying-Rossotti technique. The stability constants lie in the sequences: K_{MAL}^{MA} ?K_{ML_2 }^{ML} ; K_{MAL}^{MA_1 } > K_{MAL}^{MA_2 } > K_{MAL}^{MA_3 } \gg K_{MAL}^{MA_4 } $$ " align="middle" border="0"> and all follow the Irving-Williams stability order. These observations can be explained in terms of electrostatic interaction, change of electrophilicity of the bound metal and -acidic character of the primary ligand.     

Kinetics and mechanism of the oxidation of hydrogen peroxide by the octacyanotungstate(V) ion in alkaline aqueous media

Summary The oxidation of H₂O₂ by [W(CN)₈]^3– has been studied in aqueous media between pH 7.87 and 12.10 using both conventional and stopped-flow spectrophotometry. The reaction proceeds without generation of free radicals. The experimental overall rate law, , strongly suggests two types of mechanisms. The first pathway, characterized by the pH-dependent rate constant k _s, given by , involves the formation of [W(CN)₈· H₂O₂]^3–, [W(CN)₈· H₂O₂·W(CN)₈]^6– and [W(CN)₈· HO]^3– intermediates in rapid pre-equilibria steps, and is followed by a one-electron transfer step involving [W(CN)₈·HO]^3– (k _a) and its conjugate base [W(CN)₈·O]^4– (k _b). At 25 °C, I = 0.20 m (NaCl), the rate constant with H _a =40±6kJmol^–1 and S _a =–151±22JK^–1mol^–1; the rate constant with H _b =36±1kJmol^–1 and S _b =–136±2JK^–1mol^–1 at 25 °C, I = 0.20 m (NaCl); the acid dissociation constant of [W(CN)₈·HO]^3–, K ₅ =(5.9±1.7)×10^–10 m, with and is the first acid dissociation constant of H₂O₂. The second pathway, with rate constant, k _f, involves the formation of [W(CN)₈· HO₂]^4– and is followed by a formal two-electron redox process with [W(CN)₈]^3–. The pH-dependent rate constant, k _f, is given by . The rate constant k ₇ =23±6m ^–1 s ^–1 with and at 25°C, I = 0.20 m (NaCl).     

Kinetics and mechanism of oxidation of hydroxylamine by tetrachloroaurate(III) ion

The oxidation of H₂NOH is first-order both in [NH₃OH⁺] and [AuCl₄ ^–]. The rate is increased by the increase in [Cl^–] and decreased with increase in [H⁺]. The stoichiometry ratio, [NH₃OH⁺]/[AuCl₄ ^–], is 1. The mechanism consists of the following reactions.

Hydrogenating properties of complex rhenidm(VLI) oxides with perovskite structure

Conclusions Rhenium oxides with perovskite structure of the general formula where B^III=Y and Sm, and Ba₃LaZnReWO₁₂ containing Re(VII), exhibit catalytic activity in hydrogenation of ethyl acetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1236–1238, June, 1986.     

Kinetics and mechanism of oxidation of the chromium(III)-DL-aspartic acid complex/periodate reaction. Evidence for iron(II) catalysis

The kinetics of oxidation of the chromium(III)-DL- aspartic acid complex, [CrIIIHL]+ by periodate have been investigated in aqueous medium. In the presence of Fe^II as a catalyst, the following rate law is obeyed:

Kinetics and mechanism of the oxidation ofbis(2,4,6-tripyridyl-1,3,5-triazine)iron(II) bytrans-1,2-diaminocyclohexanetetraacetatomanganate(III) in acetate buffer

The rapid oxidation ofbis(2,4,6-tripyridyl-1,3,5-triazine)-iron(II), [Fe(TPTZ)₂]²⁺, bytrans-1,2-diaminocyclohexanetetraacetatomanganate(III), [Mn^III(Y)]⁻, in acetate buffers was monitored using stopped-flow spectrophotometry. The reaction is first order in the substrate and evidence was obtained for pre-complexation between the oxidant and the substrate. The reaction rate increases as the pH increases. Characterisation of the products using the radiotracers⁵⁴Mn and⁵⁹Fe indicated that [Mn^II(Y)]²⁻ and [Fe(TPTZ)₂]³⁺ are the final products. The reaction obeys the rate law:

Solid-solute phase equilibria in aqueous solutions,VIII: The standard gibbs energy of La2(CO3)3·8H2O

The solubilities of lanthanum carbonate La₂(CO₃)₃·8H₂O in solutionsS ₀([H⁺]=H mol kg^–1, [Na⁺]=(I–H) mol kg^–1, [ClO ₄ ^– ]=I mol kg^–1) at various fixed partial pressures of CO₂ have been investigated at 25.0 °C. The hydrogen ion molality and the total molality of La(III) ion in equilibrium with the solid phase were determined by e.m.f. and analytical methods, respectively. The stoichiometric solubility constants

Dissociation Constants of Protonated Cysteine Species in NaCl Media

The sulfur-containing biomolecule, cysteine has a role in physiological and natural environment because of its strong interactions with metals. To understand these interactions of metals with cysteine, one needs reliable dissociation constants for the protonated cysteine species [ CH(CH₂SH)COOH; H₃B⁺]. The values of dissociated constants, p , for protonated cysteine species (H₃B⁺ H⁺ + H₂B, K ₁; H₂B H⁺ + HB^–,K ₂; HB^– H⁺ + B^2–,K ₃) were determined from potentiometric measurements in NaCl solutions as a function of ionic strength, 0.5–6.0 mol-(kgH₂O)^–1 and between 5, and 45°C. The equations

Pd(PBu 3 t ) Adducts of Os3(CO)12. Synthesis and Structures of Pd2Os3(CO)12(PBu 3 t )2 and Pd3Os3(CO)12 (PBu 3 t )3

Two new compounds Pd₂Os₃(CO)₁₂ , 13 and Pd₃Os₃(CO)₁₂ , 14 have been obtained from the reaction of with Os₃(CO)₁₂ at room temperature. The products were formed by the addition of two and three groups to the Os–Os bonds of Os₃(CO)₁₂. Compounds 13 and 14 interconvert between themselves by intermolecular exchange of the groups in solution. Compounds 13 and 14 have been characterized by single crystal X-ray diffraction analyses.Dedicated to Professor Brian F. G. Johnson on the occasion of his retirement – 2005.