Dipyridyl amide-functionalized polymers prepared by ring-opening-metathesis polymerization (ROMP) for the selective extraction of mercury and palladium

Ring-opening-metathesis polymerization (ROMP) was used for the preparation of a dipyridylcarbamide-functionalized polymer suitable for solid-phase extraction of metal ions from aqueous solutions. Resins were prepared by the copolymerization of the functional monomer N,N-di-2-pyridyl-endo-norborn-2-ene-5-carboxamide (I) with 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphthalene (II), using the well-defined Schrock catalyst Mo(N-2,6-i-Pr(2)C(6)H(3))CHCMe(2)Ph(OCMe(CF(3))(2))(2) (III). The polymerization proceeds in a living manner, allowing the stoichiometric buildup of polymers. NMR investigations proved the expected backbone structure of the resulting polymers, where the binding site of the monomer remains unaffected in course of the polymerization. The new materials were investigated in terms of their complexation behavior versus a large variety of mono-, di-, tri-, and tetravalent metal ions employing UV-vis spectroscopy as well as AAS and ICP-OES techniques. The polymer-bound dipyridylamide ligand showed excellent selectivity toward Hg(2+) and Pd(2+), allowing the selective extraction of both divalent metal ions over a broad range of concentrations from complex mixtures. Due to the stability of the resulting complexes, high loadings of the material with both metals were achieved.:To elucidate the chemistry of complexation, X-ray structures of compound (I) as well as ESI-MS investigations of the complex of I with Pd(2+) were performed. I crystallized in the monoclinic space group P2(1)/c, and forms 1:1 complexes with Pd(2+) under conditions identical to the SPE experiments.