Nonbridging ligand and temperature effects on the rate of reduction of bromocobalt(III) complexes by iron(II)

Int J of Chemical Kinetics

et al. 2005

Kinetics of reduction of the surfactant complex ions, cis-chloro/bromo (dodecylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous solution was studied at 303, 308, and 313 K by spectrophotometry method under pseudo-first-order conditions, using an excess of the reductant. The second-order rate constant remains constant below critical micelle concentration (cmc), but increases with cobalt(III) concentration above cmc, and the presence of aggregation of the complex itself alters the reaction rate. The rate of reaction was not affected by the added [H + ]. Variation of ionic strength (µ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe 2+ (aq) with cobalt(III) complex proceeds by the inner-sphere mechanism.

“…The purity of the complexes was checked by cobalt [30], elemental, halide analyses, which were found to be in good agreement with that of calculated one (Table I).…”

Section: Resultssupporting

confidence: 76%

“…Iron(III) was determined [29] as the thiocyanate complex having a maximum absorption at 480 nm by reference to the calibration curve, and cobalt(II) was determined [30] as [CoCl 4 ] 2− at 690 nm in excess of hydrochloric acid. The ratio of Fe(III):Co(II) was found to be 1:1.…”

Section: Stoichiometrymentioning

confidence: 99%

Kinetics of Fe(II) reduction of cis‐halogeno(dodecylamine) bis(ethylenediamine)‐ cobalt(III) complex ion in aqueous solutions

Int J of Chemical Kinetics

et al. 2005

“…The purity of the complexes was checked by cobalt [26], elemental, halide analyses, which were found to be in good agreement with that of the calculated value ( Table 1).…”

Section: Resultssupporting

confidence: 78%

“…Iron(III) was determined [25] as the thiocyanate complex having a maximum absorption at 480 nm by reference to the calibration curve, and cobalt(II) was determined [26] as [CoCl 4 ] 2) at 690 nm in an excess of HCl. The ratio Fe III :Co II was found to be 1:1.…”

Section: Stoichiometrymentioning

confidence: 99%

Studies on Cobalt(III) Metallosurfactants. Kinetics and Mechanism of Reduction of Cobalt(III) by Iron(II) in Aqueous Acid Medium

et al. 2006

Transition Met Chem

The kinetics and mechanism of reduction of the surfactant complex ions, cis-chloro/bromo(dodecylamine)(triethylenetetramine)cobalt(III) by iron(II) in aqueous solution were studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The second-order rate constant increases with cobalt(III) concentration and the presence of aggregation of the complex itself alters the reaction rate. The reductions are acid-independent in the range [H + ] ¼ 0.05-0.25 mol dm )3 . Variation of ionic strength (l) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe 2+ (aq) with the cobalt(III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependent CMC and the standard Gibbs energy of micellization (DG 0 m ).

“…Fe III was determined spectrophotometrically by Kitson's method [40] and Co II was determined [41] as ½CoCl 4 2À at 690 nm in an excess of HCl. The ratio Fe III : Co II was found to be 1:1 in the reactions studied, indicating 1:1 stoichiometry.…”

Section: Stoichiometrymentioning

confidence: 99%

Kinetics and the Mechanism of Iron(II) Reduction of cis-α-halogeno(cetylamine) (triethylenetetramine)cobalt(III) Complex Ion in Aqueous Acid Medium

et al. 2006

Transition Met Chem

The kinetics and mechanism of iron(II) reduction of cis-a-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically in an aqueous acid medium by following the disappearance of Co III using an excess of the reductant under pseudo-first-order conditions: ½Fe II ¼ 0:25 mol dm )3 , ½H þ ¼ 0:1 mol dm )3 , ½l ¼ 1:0 mol dm )3 ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid independence in the range ½H þ =0.05-0.25 mol dm )3 . The second order rate constant increased with Co III concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of ½Fe II ; ½H þ and [l] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of Fe 2þ ðaqÞ with Co III complex proceeds by an inner-sphere mechanism.