Preparation, spectrum, and stability of indium(I) in aqueous solution

Abstract

Details of the preparation of ca. 3 × 10^–4M-solutions of indium(I) by anodization of an indium electrode are described. The spectrum of indium(I) in aqueous perchlorate media (ε= 2·56 × 10⁴ at 209 nm.) is compared with spectrum of indium(II)(ε= 9·5 × 10³ at 262 nm.) obtained by pulse radiolysis of a solution of indium(III)(ε= 0·73 at 243 nm.). Beer's Law is obeyed at wavelengths in the range 205–275 nm. for the range of indium(I) concentrations investigated (zero to 2 × 10^–4M), and there is no evidence for any significant build-up of indium(II) in such solutions. The kinetics of the indium(I) reduction of hydrogen-ions, In^I+ 2H⁺→ In^III+ H₂ have been studied using conventional spectrophotometric techniques. The rate law is of the form d[In^I]/dt=k[In^I][H⁺]; there is no evidence for an indium(III) dependence with the latter present initially in 200-fold excess. At 25·1 and µ= 0·7M(LiClO₄), k= 11·2 × 10^–3 I. mole^–1 sec.^–1, ΔH^‡= 10·2 (±0·4) kcal. mole^–1 and ΔS^‡=–33·3 (±1·1) e.u. These values are in good agreement with those obtained previously with a polarographic technique.