RAMAN SPECTROSCOPIC STUDY OF STEPWISE BROMIDE AND CHLORIDE COMPLEXES OF INDIUM(3) IN AQUEOUS SOLUTION

From measured Raman frequencies and intensities in aqueous indium bromide solutions, three complexes were detected. These were indicated to be InBr2+, InBr2+, and InBr3. That no anionic complexes were present was confirmed by the lack of anionic migration, which however was found for the corresponding chloride system. Three complexes were also detected in the chloride system, which were indicated to be InCl2+, InCl2+, and InCl4-. However, the last of these is not the tetrahedral ion known to exist in ether and nonaqueous solvents. Raman experiments in methanol-water mixtures suggest that, in the presence of water, InCl4- coordinates water molecules. This behavior accounts for both the Raman results and the relatively poor extractability of InCl4- from water. In addition, absolute Raman intensities are given and discussed for InCl4- and InBr4- in nonaqueous solvents, and equilibrium quotients are determined for stepwise complex formation in water. © 1969, American Chemical Society. All rights reserved.