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

Abstract

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.