Reactivity of Hexachloroiridate(IV) in Alkaline Medium

Abstract

The reduction of hexachloroiridate(IV) in alkaline medium wasstudied in the temperature range 298-313 K. The reaction is firstorder with respect to [lrCl₆^2-) and [OH^-). The rate increases withthe increase in ionic strength. Plot of logarithm of rate constantagainst reciprocal of dielectric constant yields a good straight linewith negative slope up to dielectric constant of ca. 44.4 beyondwhich the line bends. The values of  ΔH^≠ and  ΔS^≠ are 59 ± 4 kJmol^-1 and -57 ± 14 JK^-1 mol^-1 respectively. Hexachloroiridate(lV)is reduced to hexachloroiridate(III) by outer sphere mechanisticpath. The reaction appears to proceed through the intermediate formationof free radicals to give products.