EFFECT OF PH ON THE REDOX PROPERTIES OF TRINUCLEAR IRIDIUM MU(3)-OXOHEXAACETATES - POTENTIOSTATIC COULOMETRIC DETERMINATION OF IRIDIUM IN ACETATE SOLUTIONS

A study with the use of cyclic voltammetry and electronic absorption s pectroscopy showed that pH and the CH3COONa concentration in solution exert a strong effect on the redox properties of trinuclear iridium ox ohexaacetates [Ir-3(mu(3)-O)(CH3COO)(6)L(3)](n) (L = CH3COOH, CH3COO-, and H2O). It was found that an increase in pH from 1.5 to 13 results in the successive deprotonation of CH3COOH and H2O, accompanied by a s hift of the oxidation potentials of iridium acetate complexes to less positive values. A technique for the potentiostatic coulometric determ ination of iridium at a Pt electrode in acetate solutions (0.20 - 2.00 mg; RSD = 3%) based on the redox reaction in the system of complex Ir -3(III, IV, IV)/Ir-3(III, III, III) acetates was proposed. Predominant amounts of Pt, Pd, and Ru do not interfere with the determination; Rh and Cu are interferents. Both Cr and Fe can be present in amounts not exceeding the ratios Ir:Cr:Fe = 1:0.5:10.