Solvent extraction of divalent palladium and platinum from aqueous solutions of their chloro complexes using an N,N-dimethyldithiocarbamoylethoxy substituted calix[4] arene

The compound 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-bromoethoxy) calix[4] arene has been prepared by first converting 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-hydroxyethoxy) calix [4] areneinto the tosylate, and then to the product by reaction with LiBr. The compound crystallizes in the trigonal space group P3(2)21 with a=13.160(1), b=13.160(2), c=25.595(6) Angstrom, alpha=90.00(2), beta = 90.00( 1), gamma = 120.000(9)degrees, Z = 3, P-calc = 1.40 g cm(-3). The final R value for 2391 unique reflections was 0.061. The compound reacts with excess sodium N,N-dimethyldithiocarbamate to give 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-(2-N,N-dimethyldithiocarbamoylethoxy) calix[4]arene. This compound is an effective extractant for transferring palladium(II) from an aqueous to a chloroform phase. No extraction of PtCl42- is observed under thermal conditions. Under photochemical conditions using a mixture of PtCl62-, and PtCl42-, extraction of platinum into the chloroform layer is observed. An explanation for this observation is given.