Upper rim thioether derivatives of calix[4,6]arenes: Extraction of fission Pd(II) and Ag(I)

We report studies on the Pd(II) and Ag(I) complexation and extraction by tetraalkyl(tolyl)thiomethylcalix[4]arenes (1-c) stabilized in the cone conformation, and by the stereochemically mobile tetraalkyl(tolyl)thiomethylcalix[6]arenes (2a, b). These are found to be 100-1000 times more efficient as extractants of nitric and nitrous forms of Pd(II) and Ag(I) than their ungrafted monodentate analogues. Extraction experiments performed on real HLW show that tetrabutylthiomethylcalix[4]arene 1b is able to concentrate and separate Pd from main fission products. The extraction constants for mono- and binuclear Ag complexes have been determined. The stoichiometry and structural features of the complexes of Pd and Ag have been studied experimentally by extraction, IR- and mass-spectroscopy methods as well as in quantum-mechanical calculations.