Kinetic studies on 4d and 5d transition-metal complexes. Part VII. Kinetics of the reactions of chloro- and bromo-penta-ammineiridium(III) perchlorates with sodium hydroxide in aqueous solutions

Abstract

The kinetics of the reactions of [lr(NH₃)₅Cl]²⁺ and [lr(NH₃)₅Br]²⁺ with hydroxide ions are reported. Data were obtained in the temperature range 76–97 °C under conditions which allow extrapolation to zero ionic strength. The variation of the rate constants (units of l mol^–1 s^–1) at zero ionic strength are reproduced by the equations: for [lr(NH₃)₅Cl]²⁺, k°₂= 2·262 × 10¹⁷ exp –(33,657 ± 700)/RT; and for [lr(NH₃)₅Br]²⁺, k°₂= 1·258 × 10¹⁸ exp –(35,153 ± 800)/RT. A good linear correlation exists between the entropies of activation of the reactions of a variety of acidopenta-ammine complexes and the entropies of hydration of the replaced ligands.