The reduction of hexanitrocobaltate(III) ion in the presence of hexadecyltrimethylammonium bromide

The influence of cationic surfactant hexadecyltrimethylammonium bromide (CTAB) on the kinetics of the spontaneous reduction of the analytically important compound, sodium hexanitrocobaltate(III), was studied. The spontaneous reduction was monitored spectrophotometrically at pH 2 and 5 and at concentrations of CTAB from 1 × 10⁻⁵ to 5 × 10⁻⁴ M. The mechanism of this process was described using two consecutive first-order reactions. A decrease in the rate constant for reduction at pH 5 in solutions containing CTAB in concentrations of 5.6 × 10⁻⁵ M (critical micelle concentration) compared with its rate in an aqueous solution was observed. These effects could be explained by electrostatic and hydrophobic/hydrophilic interactions between the micellar pseudophase and the hexanitrocobaltate(III) ion. The article is published in the original.     

Thermal decomposition of potassium chlorate in presence of chromium(III) oxide and nickel(II) chromite(III)

A study of thermal behaviour of intimate mixtures of different molar ratios of potassium chlorate and chromium(III) oxide, and potassium chlorate and nickel(II) chromite(III) was made by employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray powder diffraction analysis. Potassium chlorate in presence of Cr(III), starts decomposing around 200°C which is much below the decomposition temperature of pure KClO₃. Each mole of Cr(III) takes up 8/3 moles of KClO₃ to become oxidized into potassium dichromate.     

Polarographic reduction of cobalt(II) ion in presence of resacetophenoneoxime

Analytical and Bioanalytical Chemistry -     

Homogeneous catalytic reduction of NO in the presence of Co(III) complexes

Several Co(III) complexes have been found to be active catalysts in the reaction of NO with n-butylamine. N₂ and N₂O were identified as gaseous products of the reduction. Isotope scrambling in N₂ and N₂O in the experiments with N-15 enriched NO suggests two types of stoichiometric processes. The catalysis is interpreted by formation of a NO-complex as intermediate.     

On the polarographic reduction of nitrate ion in the presence of zirconium(IV)

The polarographic reduction of nitrate ion in the presence of zirconium(IV) is studied by dc and phase-selective ac polarography. The total reduction process was proved by means of controlled-potential electrolysis and chemical analysis to conform to NO⁻₃+8H⁺6e⁻→NH₂OHH⁺=2 H₂O. Using a measurement of differential capacity, a large part of the difference between the reduction transfer to the vicinity of the electrode but to a charge transfer step and/or a chemical reaction step. The zirconium(IV) is concluded to act as an intermediary for the charge transfer from the electrode to the nitrate ion.     

Nanosized thermometric NMR sensors based on the paramagnetic complex ion pairs of lanthanides(III) for temperature determinations in low-polar nonaqueous solutions

For temperature determination in solutions it is suggested that the temperature dependence of the paramagnetic lanthanide-induced shifts (LIS) in the NMR spectra on the ligand nuclei be used for [Ln(PTA)₂(18-crown-6)]⁺[Ln(PTA)₄]^? complex ion pairs formed in CCl₄, CDCl₃, CD₂Cl₂, CD₃C₆D₅, and C₂D₃N type low-polar solvents (Ln = La, Ce, Pr, Nd, Eu; PTA is the pivalyltrifluoroacetonato anion). It was found experimentally that the [Ln(PTA)₂(18-crown-6)]⁺ complex cation molecules (Ln = Ce and Pr) proved most suitable for use as nanosized (≈1.1 nm) probes for temperature determinations in nonaqueous solutions. A linear dependence of the LIS on the ¹H nuclei of different groups and the difference between the LIS corresponding to the CH₂ groups of the 18-crown-6 molecules and the CH groups of the PTA anions on the reciprocal temperature (1/T) was found. The LIS of the individual signals of different groups in Ln paramagnetic complexes (relative to the signals of the diamagnetic analogs, e.g., La or Lu) may be used for temperature control in the sample, although the temperature measurement error is smaller (≤ 0.04 K) when the difference between the LIS of the CH₂ and CH groups is used. Due to the high thermodynamic and kinetic stability combined with small sizes of [Ln(PTA)₂(18-crown-6)]⁺[Ln(PTA)₄]^? molecules in nonaqueous solutions, these compounds may be used as thermometric NMR sensors directly in reaction media for in situ control over temperature.     

The kinetics of aquation of cis-ammine-bromobis(ethylenediamine) cobalt(III) ion in water-organic mixtures

The aquation kinetics of cis-[CoNH₃Br(en)₂]²⁺ were investigated in aqueous mixtures of ethyl alcohol, isopropyl alcohol, t-butylalcohol and acetonitrile. The rate constants, activation enthalpies and entropies were determined. The interpretation of the experimental data, based on electrostatic theory, was possible only when methyl alcohol and ethyl alcohol were used as co-solvents. It was shown that in the mechanism of reaction studied non-electrostatic interactions play an important role.     

The extraction of Yb(III) and Lu(III) with chloroform from aqueous solutions in the presence of cupferron

The equilibrium of distribution of Yb(III) and Lu(III) between chloroform and the aqueous phase in the presence of cupferron (the ammonium salt of N-nitrosophenylhydroxylamine) were studied as apH function of the aqueous phase and the concentration of N-nitrosophenylhydroxylamine (HL). The stability constants for theLnL _n ^3–n ) complexes (n=1÷3) being formed in the aqueous phase were established, as well as the equilibrium constants of the extraction reaction $$Ln(H_2 O)_m^{3 + } + 3HL_{(O)} \mathop \rightleftharpoons \limits^{K_{ex} } LnL_{3(O)} + 3H^ + + mH_2 O(Ln^{3 + } = Yb,Lu),$$ two-phase stability constants for theLnL ₃ complexes,pH _0.5 and the separation factor Lu(III) from Yb(III).     

Redox kinetics of metal complexes in nonaqueous solutions. V. Kinetics and mechanism of the iron (II) reduction of the acetylacetonates of manganese (III) and cobalt (III) in acetonitrile

The electron transfer step of the reduction of Mn(acac)₃ and Co(acac)₃ by Fe(II) in acetonitrile is preceded by the one-ended dissociation of an acac ligand and the formation of a binuclear bridged complex. After the electron transfer has taken place through the bridging ligand, the complex dissociates into the products M(acac)₂ (M = Mn, Co) and Fe(acac)²⁺. These primary reaction products could not be identified, since the transfer of acac from M(acac)₂ to Fe(acac)²⁺ is too rapid, producing ultimately Fe(acac)₃ and M²⁺. The M(III)-oxygen cleavage is accelerated by M(acac)₂. Furthermore, the dissociation of the binuclear intermediate is catalyzed by the M(acac)₃ reactant. Mn(acac)₃ is reduced more than a thousand times faster than Co(acac)₃.     

Electron transfer at tetrahedral cobalt(II), part IV: kinetics of silver(I) catalysed chlorate reduction

Summary The very slow reduction of ClO _inf3 ^su– by [CoW₁₂O₄₀]^6- is markedly catalysed by Ag¹ in aqueous HClO₄ solution at I = 1.0 M (NaClO₄). The reaction obeys the rate law: -d[reductant]/dt where a = (1.28 ± 0.10) × 10^-4M^-1s^-1 and b = (2.22 ± 0.20) × 10^-4M^-3s^-1, at T = 60.1 ± 0.1°C and [H⁺] = 0.10–1.50 M. Activation parameters have been determined for each pathway and the reaction is discussed in terms of the outer-sphere mechanism.Part III: ref. 1.     

Kinetics of the interaction of aquo-ethylenediaminetetraacetatoruthenate(III) with ferricyanide ion in water

Summary The interaction of aquo-ethylenediaminetetraacetatoruthenate(III) with ferricyanide ion was studied spectrophotometrically as a function of ferricyanide ion concentration, pH (1.5–8.5) and temperature (30–45°C) at ionic strength 0.2 M (NaClO₄). Kinetic and activation parameters (H=27.1±1.75 KJ mol^–1, S=–136.7±5.57 J mol^–1 deg^–1) are consistent with the proposed mechanism.