Kinetics of aquation of Cis- and trans-tetrachlorodipyridineiridate(III) anions and chloride anation of cis- and trans-trichloroaquodipyridineiridium(III)

Abstract

The kinetics of the reactions trans- Ir(py) 2 Cl 4 −4+ H 2 O ⇌ k31 k13 trans- Ir(py) 2 OH 2 Cl 3 + Cl − were studied in 0·01–3·7 F HCl or HClO 4 (μ = 0·01–3·7, NaCl and/or NaClO 4) at 110·00°C. In 0·5 F HCl (μ = 3·7), k 13 = (8±1) × 10 −5 sec −1 and k 31 = (4·4 ± 0·8) × 10 −4 M −1 sec −1, nearly independent of C 0 (0·02-0·5 mF), [H +] (0·1-0·5 F, at 1·7 F Cl −), and [Cl −] (0·5-3·7 F H +); increase of μ(0·5-3·7) increases k 31, but has only a small effect on k 13. The kinetics of aquation of cis-Ir(py) 2-Cl 4 − was examined in 1–2·5 F HClO 4 (μ = 1–3·7, NaClO 4) at 90–110°C. The products are 5% trans-, 28% cis(sun)-, and 67% cis(autoclave)-Ir(py) 2(OH 2)Cl 3; the former is formed directly, but relative amounts of the latter two isomers are apparently determined by their faster isomerization. The total aquation rate constant is (1·3 ± 0·1) × 10 −4 sec −1 at 110·00°C in 1 F HClO 4 (μ = 3·7), nearly independent of C 0 (0·02-1·6 mF), [H +](1–2·5 F), and μ(1–3·7); E a = 34 ± 4 kcal mole −1, log PZ (sec −1) = 15·5 ± 2·3. Chloride anation of cis(autoclave)-Ir(py) 2(OH 2)Cl 3 is complicated by competing isomerization. At 110·00°C the anation rate constant appears to be ca. 2 × 10 −4 M −1 sec −1 in 1 F H + (μ = 3·7) from 0·5-3·7 F Cl −. Accurate u.v. and visible absorption spectra of the complexes are presented.