Mixed iron-nickel complexes in Versatic 10 solutions

Abstract

Iron and nickel Versatic solutions were prepared by solvent extraction with 33% Versatic 10 in Escaid 110. Mixed iron-nickel Versatic solutions with different iron:nickel ratios were prepared by mixing single metal solutions. The infrared spectra of the single metal and mixed metal Versatic solutions were recorded at 25 and 160°C. Iron Versatic showed absorption bands at 1685, 1575 and 1418 cm −1, probably due to solvating acid, bidentate chelation and bidentate bridging, respectively. Nickel Versatic absorbed at 1665 and 1590 cm −1; the 1590 cm −1 band has been assigned to monodentate coordination. All mixed iron-nickel solutions showed absorption bands at 1610 and 1585 cm −1. The relative intensities of the bands changed with solution composition, but not the frequencies. The mixtures showed none of the absorption bands of iron-only or nickel-only Versatic solutions; thus all the metal ions in solution are assumed to be present as mixed complexes. The average Versatic to total metal charge ratio in the complexes at 160°C was 1.1–1.3 for relatively high metal concentrations. Thin layer chromatography tests were carried out at 25°C; the retention factors of all mixed iron-nickel solutions were the same, and different from those of iron-only or nickel-only Versatic. This gives further evidence for the existence of mixed-metal complexes.