Studies on the Preparation of Cuprous Oxide. VIII. A Spectrophotometric Study of Halogenocopper(I) Complexes in Aqueous 5 M Na(ClO4) Solutions

Article abstract of DOI:10.1246/bcsj.53.2514

The complex formation of copper(I) with bromide and iodide ions in aqueous 5M (1M = 1 mol dm^-3) Na(ClO4) solutions was studied spectrophotometrically over a pH range from acidic to alkaline.Over the concentration range of 0.05-5 M bromide ions in acidic solutions, the CuBr2^- and CuBr3^2- complexes were found.On the other hand, in the iodide system the CuI2^-, CuI3^2- complexes and a higher complex were found under the same experimental conditions, although the composition and the formation constant of the last complex could not be determined in this study.The equilibrium constants for the reactions, CuX2^- + X^- = CuX3^2-, were 13 and 1.6 for the bromide and iodide complexes respectively.A hydrolyzed species of copper(I), Cu(OH)2^-, was found in an alkaline solution of the two systems.The formation constants, β_-22 = ->->²/->->², were evaluated as follows: β_-22 = (10.0 +/- 0.7) * 10⁷ (-> less than 2 M), (2.6 +/- 0.7) * 10⁷ (-> = 3M), (1.7 +/- 0.7) * 10⁷ (-> = 4M) in the bromide solutions, (4.0 +/- 0.4) * 10³ (-> less than 2M), (2.5 +/- 0.4) * 10³ (-> = 3M), (2.2 +/- 0.4) * 10³ (-> = 4M) in the iodide solutions.