Liquid-liquid extraction of copper(II) with cyclic tetrathioethers

Abstract

Liquid-liquid extraction of the divalent metal ions manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) with 1,4,8,11-tetrathiacyclotetradecane was examined using the tetraphenylborate ion (TPB −) for the formation of the ion pairs. Copper(II) was quantitatively extracted into 1,2-dichloroethane, whereas the other metals were hardly extracted. The extraction behaviour of copper(II) with 12–16-membered cyclic tetrathioethers ([ n]aneS 4, where n represents the total number of carbon and sulphur atoms int he cyclic ligand ring) was examined. Chloroform and 1,2-dichloroethane were used as extraction solvents. The order of the extractability of copper(II) was as follows: [15]aneS 4 > [16]aneS 4 > [14]aneS 4 > [13]aneS 4 > [12]aneS 4 > at 2.5 × 10 −4 M of ligands, [16] aneS 4 > [15]aneS 4 > [14]aneS 4 > [13]aneS 4 > [12]aneS 4 at 2.5 × 10 −5 M of ligands. The extracted species were examined at ligand concentrations higher than 2.5 × 10 −4 M. Copper(II) was extracted with [13]aneS 4 and [16]aneS 4 as [CuL 2] 2+ (TPB −) 2 and [CuL 4] 2+ (TPB −) 2 depending upon the relative concentration of the ligand to copper(II). Where L represents cyclic tetrathioethers. The extracted species with [14]aneS 4 and [15]aneS 4 were [CuL 2] 2+(TPB −) 2 and [CuL 4] 2+(TPB −) 2, respectively. In case of [12]aneS 4, the following three species were observed depending upon concentrations of the ligand and TPB −: [CuL 2(OH)] +TPB −, [CuL 2] 2+(TPB −) 2 and [CuL 4] 2+ (TPB −) 2.