Showing papers on "Aquation published in 1993"

The component of "ruthenium red" responsible for inhibition of mitochondrial calcium ion transport. Spectra, electrochemistry, and aquation kinetics. Crystal structure of .mu.-O-[(HCO2)(NH3)4Ru]2Cl3

Abstract: The cytological stain, ruthenium red, effectively inihibits mitochondrial Ca 2+ aq uptake; however, the majority of this activity has been attributed to an impurity. This component has now been isolated and a derivative, μ-O-[(HCO 2 )(NH 3 ) 4 Ru] 2 Cl 3 , characterized by X-ray diffraction, spectroscopy, and electrochemistry. The compound crystallizes in the orthorhombic space group Pnn2 (No. 34), with unit cell constants of a=8.588 (1), b=13.335 (2), c=7.602 (2) A, Z=2, and R=0.024. The bridging Ru-O bond is quite short (1.8240(6) A), while the Ru-O formate bond length (2.033(3) A) is typical for a Ru-O single bond

Oxo complexes, pH effects, and catalysis in films formed by electropolymerization

Abstract: Electrodes coated with thin polymeric films of 1/3poly-cis-[Ru(vbpy) 2 (H 2 O) 2 ] 2+ -co-2/3poly-[Ru(vbpy) 3 ] 2+ (vbpy is 4-methyl-4'-vinyl-2,2'-bipyridine) or poly-cis-[Ru(pyr-bpy) 2 (H 2 O) 2 ] 2+ (pyr-bpy is 4-(2-pyrrol-1-yl-ethyl)-4'-methyl2,2'-bipyridine) have been prepared and characterized by electrochemical and spectroscopic measurements. Stepwise aquation of the precursor, poly-cis-[Ru(pyr-bpy) 2 Cl 2 ], occurs, but only after oxidative excursions through the Ru III/II wave

Kinetics and mechanism of oxidation of hydroxylamine by hexachloroiridate(IV) ion in buffer solutions

Abstract: The oxidation of hydroxylammonium ion by [IrCl6]2− ion in acetic acid – acetate buffer solutions, studied by stopped flow, has the stoichiometric ratio Δ[IrCl6]2−/Δ[NH2OH] = 1. The oxidation involves the species [IrCl6]2− and NH3OH+ although spectral analysis of the spent reaction mixture indicates [IrCl5(OH2)]2− to be the main product (almost to the extent of 80%). This anomaly arises because of the aquation of the reduced product [IrCl6]3−. The rate is retarded both by H+ and Cl− ions and the plots of against respective concentrations are linear. The proposed mechanism is given by reactions [i]–[v].The values of the rate constants at 25 °C are as follows: k1 = 147 dm3 mol−1 s−1 and 102ketKia = 2.8 s−1. The related activation parameters are , and,, and and , respectively. The value of Kipd is 2.91 ± 0.03 mol dm−3 and that of Kipa (= 1/Kipd) is 0.344 ± 0.004 dm3 mol−1; both values are almost independent of temperature.

Aquated block isocyanate having low-temperature extensibility and paint composition using the same

Abstract: PURPOSE:To obtain the subject polymer having excellent weather resistance, chemical resistance and coating film properties at low temperature and useful as a water paint for automobile, etc., by blocking a non-yellowing polyisocyanate with a blocking agent and aquating the product with an aquation assistant. CONSTITUTION:The objective polymer is produced by reacting (A) a diol or triol having a number-average molecular weight of 500-1,600 (e.g. polyether polyol) with (B) an aliphatic or alicyclic diisocyanate or their mixture (preferably 1,6-hexamethylene diisocyanate), blocking the NCO group of the obtained polyisocyanate with (C) a blocking agent (preferably methyl ethyl ketoxide) and aquating the obtained blocked isocyanate with an aquation assistant (preferably PVA, polyoxyethylene alkylphenyl ether, etc., having number- average molecular weight of 5,000-300,000 and a saponification degree of <=90%).

Iron(II)-diimine complexes: solvatochromism and reactivity

Abstract: Reactivity trends are reported for aquation of tris(5-nitro-1,10-phenanthroline)iron(II) in ternary H2O-t-BuOH-polyethyleneglycol (PEG400) solvent media. Wavelengths of maximum absorption for the lowest energy charge-transfer band of dicyanobis(2-acetylpyridineoximato)-iron(II) are reported for the same series of ternary solvent mixtures. There is no overall correlation of rate constants with wavelength shifts, indicating that solvation effects in the two systems are not directly related.

Solvation and steric effects on electrophilic reactivity of ethylenic compounds. Part 4. Bromination of oct-1-ene in anionic microemulsions

Abstract: The kinetics and product distribution of the bromination of oct-1-ene in anionic sodium dodecyl-sulfate (SDS)–butanol–hexane–water and sodium bis (2-ethylhexyl)sulfosuccinate (AOT)–isooctane–water microemulsions are reported. Dibromide and solvent-incorporated products are formed. In both kinds of microemulsion, the dibromide yield decreases smoothly from 100% to 10% as the water content of the reaction medium increases from 0% to 65%, whereas in pure water or butanol it is greater than 80%. The regioselectivity of the water- or butanol-incoporated products is 70:30 Markownikoff:anti-Markownikoff, a ratio identical with that found in pure methanol, butanol or water. Kinetic bromide-ion effects on the reaction in a water-rich (75%) SDS microemulsion, show that bromination occurs in the interfacial oil–water region, and not in one of the two microphases, the only brominating agent being molecular bromine and not the tribromide ion. The overall bromination rate constant in this SDS microemulsion (k= 1.6 × 104 dm3 mol–1 s–1) is smaller than that in pure water (2.3 × 107 dm3 mol–1 s–1) and in SDS micelles (2 × 105 dm3 mol–1 s–1), in the same range as that in a 80–20 methanol–water mixture, and greater than that in butanol (2 × 102 dm3 mol–1 s–1). These results are discussed in terms of the particular characteristics (ionization and dissociating abilities, aquation and water properties) of the microemulsion interfaces.

Electrochemical Study of cis-Cyanoaquobis(ethylenediamine)chromium(III) Ion and Its Adducts with Hg(II) and Ag(I)

Abstract: Electrochemical properties of [Cr(CN 2 )(en) 2 ] + are described. Reactions of this complex with Hg(II) and Ag(I) were studied. Their stoichiometry (1 : 1) was determined using potentiometric and amperometric titration. Different pulse voltammetry (DPV) was applied to identify their products - dinuclear adducts. It was concluded on the bases of DPV experiments that linkage isomerization of bridding cyano ligand occurs in the process of adducts formation. The decomposition (aquation) of these adducts was followed and the influence of H + and Hg 2+ concentration on its rate was measured and discussed. The paper also deals with a spontaneous isomerization of unstable CN linkage isomers Cr(NC) 2 and Cr(CN)(CN) to the stable isomer Cr(NC) 2 .

Reaction kinetics of macrocyclic silver(II) complexes. Part I. Acid aquation of the [Ag(II)([15]aneN 4 )] 2+ cation and its reaction with peroxodisulphate.

Abstract: The decomposition kinetics of the [Ag(II)L] 2+ cation (where L = [15]aneN 4 ) has been studied as a function of [H + ] and temperature, in aqueous perchlorate media (ionic strength = 1.00 mol dm −3 ). The decomposition follows the second-order rate, law, Rate = k[H + ][Ag(II)L 2+ ], where k = (6.65 ± 0.11) × 10 −6 dm 3 mol −1 s −1 at 298.2 K. From the temperature dependence, an activation energy of 89.0 ± 0.7 kJ mol −1 has been determined. The silver(II) complex reaction with peroxodisulphate has also been studied in aqueous perchlorate media

Kinetics of the dissociation of tris(1,10-phenanthroline) iron(III) complex ion in aqueous acid solutions. A mechanistic model for product specificity

Abstract: The natural decay of Fe(phen) f3 p3+ , where no CeIV is employed for scavenging the side reaction product, Fe(phen) f3 p2+ , is now treated as a complex reaction involving two parallel processes, and the experimental kinetics are consistent with the rate laws derived from a mechanism that simultaneously explains the composition of the products as a function of acidity. In terms of the proposed mechanism the dissociation rate of the complex ion in acid solutions containing CeIV as scavenging agent is to be regarded as a CeIV retarded aquation rate, and OH− is to be assigned a catalytic role in the kinetics of basic reduction.

Kinetics of acid- and iron(III)-catalysed aquation of cis-(salicylato)-(methyl/ethylamine)bis(ethylenediamine)cobalt(III)

Abstract: The kinetics of spontaneous, acid- and FeIII-catalysed aquation of cis-[Co(en)2(RNH2)(SalH)]2+ complexes (R = Me, Et; SalH = C6H4(OH)COinf2sup-) were studied in acid perchlorate medium, I = 1.5 mol dm−3 (NaClO4) at 70–80°C. The FeIII-catalysed aquation proceeds via formation of a binuclear species, the evidence of which follows from aquation, complexation and equilibrium studies. The spontaneous aquation rate shows steric acceleration with the increase of the nonlabile amine chain length, while that of acid- and FeIII-catalysed aquation shows the opposite trend. An attempt is made to explain the discrepancy in the rate on the basis of solvent cosphere effects.

Kinetics and mechanism of aqua ligand substitution reactions from cis-diaqua-bis(bipyridine)ruthenium(II) ion by pyridine-2-aldoxime in aqueous medium

Abstract: The kinetic behaviour of cis-[Ru(bipy)2(H2O)2]2+ towards the anating ligand pyridine-2-aldoxime as a function of temperature, ligand concentration, substrate complex concentration and pH is reported and the rate expression Rate = k1k2[Ru(bipy)2(H2O)2]2+ [LL]/(k-1 + k2[LL]) is established where k1 is the water dissociation rate constant for the slow step, k-1 is the rate constant for the aquation, k2 is the ligand-capturing rate constant of the five-coordinate intermediate [Ru(bipy)2(H2O)]2+ and LL is pyridine-2-aldoxime. The reaction is pH-dependent in the pH range 3.65–5.50. The enthalpy and entropy of activation were obtained using Eyring plots. The results are in conformity with a dissociative mechanism.

Kinetic and solvatochromic behaviour of low-spin iron(II) complexes of pyridineoximate and dioximate ligands

Abstract: Kinetic results are presented for dissociation (aquation) of low-spin tris-diimine-iron(II) complexes derived from 2-pyridinealdoxime, 2-acetylpyridineketoxime and 2-benzoylpyridineketoxime in acidic aqueous and mixed aqueous media. The preparation and solvatochromic behaviour are described for ternary bis-diimine-dicyano-iron(II) complexes derived from 2-acetylpyridineketoxime and from four dioximes. These results are considered in relation to hydration and (selective) solvation of these ligands and their complexes.

Ruthenium(III) Chloride in Aqueous Solution: Effects of Temperature, Ionic Strength and Solvent Isotope on Aquation and Anation Reactions of the Chloro Complexes.

Abstract: The kinetics of aquation and anation of [RuCl 4 (H 2 O) 2 ] − ( 1 ), [RuCl 3 (H 2 O) 3 ] ( 2 ), [RuCl 2 (H 2 O) 4 ] + ( 3 ) and [RuCl(H 2 O) 5 ] 2+ ( 4 ) species were studied spectrophotometrically at 288, 298, 308 and 318 K and the activation parameters corresponding to these reactions determined. Effects of ionic strength (0.02–0.2 M KCl) and solvent isotope ( k H 2 O / k D 2 O ) on aquation and anation processes of 1–4 were investigated at 308 K. The data were interpreted and discussed in support of the mechanistic steps proposed for these reactions. A linear free energy relationship between the thermodynamic data corresponding to the rate steps was also obtained.