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

The liquid-liquid extraction of platinum(II) with 12-, 14- and 16-membered cyclic tetrathioethers from chloride solution was studied. Bromocresol Green ion as a counter anion and 1,2-dichloroethane as an extraction solvent were used. The effect of thiourea on the extraction rate of platinum(II) was examined. Platinum(II) was hardly extracted with macrocyclic tetrathioethers in the absence of thiourea because of the slow extraction rate. The extraction rate of platinum(II) was considerably enhanced by the addition of thiourea. The extraction rate of platinum(II) with 16-membered cyclic tetrathioether was faster than that with 12- and 14-membered ones. Platinum(II) was quantitatively extracted with 16-membered cyclic tetrathioether into 1,2-dichloroethane within 5 h in the presence of thiourea.