Supercritical Carbon Dioxide-Soluble Ligands for Extracting Actinide Metal Ions from Porous Solids

The focus of the effort during the project period from 9/16/98 to 6/15/99 has been on the synthesis, aggregation, and coordination chemistry of silyl-containing diphosphonic acids that potentially could be useful as solvent extraction reagents in supercritical CO2. A homologous series of alkylenediphosphonic acids was esterified with 3-(trimethylsilyl)-1- propanol to the symmetrically-substituted diesters. The silicon-containing alcohol 3- (trimethylsilyl)-1-propanol was chosen for esterification of the diphosphonic acids because it contains both a silyl group and a trimethylene linker. Separating the trimethylsilyl from the organo-functional group by three carbon atoms is optimal for achieving chemical stability and synthetic accessibility. The synthesis of these compounds utilizes methodology that relies on dicyclohexylcarbodiimide as the esterification reagent to activate the acid