LIQUID-LIQUID-EXTRACTION OF COPPER(II) WITH CYCLIC TETRATHIOETHERS

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 in the 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]ane(S) > [13]aneS(4) > [12]aneS(4) at 2.5 x 10(-4) M of ligands, [16]aneS(4) > [15]aneS(4) > [14]aneS(4) > [13]aneS(4) > [12]aneS(4) at 2.5 x 10(-5) M of ligands. The extracted species were examined at ligand concentrations higher than 2.5 x 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-), 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-)-T-+, [CuL(2)](2+)(TPB-)(2) and [CuL(4)](2+)(TPB-)(2).