Synthesis of α-, β-, and γ-Ketophosphonate Polymer-Supported Reagents:  The Role of Intra-ligand Cooperation in the Complexation of Metal Ions

Bifunctional ligands, viz., α-, β-, and γ-ketophosphonic acids, wherein a carbonyl group is systematically separated from a phosphoryl group with methylene moieties, have been immobilized on cross-linked polystyrene beads via the Arbusov and Perkow reactions. Studies with Eu(III), Cu(II), Pb(II), Cd(II), Co(II), and Ag(I) in various acid solutions show that under conditions where coordination is the dominant mode of metal ion sorption, the α-ketophosphonate complexes greater levels of metal ions than the β-ketophosphonate and both complex far greater levels of ions than the γ-ketophosphonate. The latter performs in a manner comparable to the monofunctional phosphonic acid resin. The results are consistent with intra-ligand cooperation being an important factor in the design of polymer-supported reagents for the complexation of high levels of metal ions.