The study of transition elements: Synthesis of rhenium tetra hydride complex and ion exchange of molybdenum with resins.

摘要

In this thesis, we studied the chemistry of two transition metals: Rhenium and Molybdenum. In the first project, we synthesized rhenium silyl complexes from silanes and metal hydrides of rhenium to explore the chemistry of the resulting silyl-stabilized compounds; in the second project, we studied the chemistry of molybdenum in uranium barren solutions, particularly the ion-exchange of molybdenum with three different types of resins.;In studying the chemistry of rhenium complex, we developed a simple synthetic technique for the preparation of rheniumtetrahydride complex. We started with ReH7(PPh3)2, which reacted with triphenylsilane to form an intermediate, ReH6(SiPh3)(PPh3) 2. This intermediate reacted further with pyridine to form the final product, ReH4(SiPh3)(PPh3)2Py. In 1H NMR a broad triplet splitting at -4.45 ppm indicates the four hydrogens bonded directly to the central rhenium atom, while the two small resonances in the aromatic region of (7.1 ppm & 7.7 ppm) indicate the presence of pyridine bound to rhenium. The triplet pattern at -4.45 ppm (which is broad at room temperature, unlike the starting material) suggests the presence of two triphenylphosphine ligands close to the hydride ligands bound to rhenium.;In studying the ion-exchange of molybdenum, three polymer based resins are tested for the removal of molybdenum from alkaline leach Uranium barren solutions. The three resins, DOWEX 21K, DOWEX 21K XLT and XUR-1525, are copolymer of styrene and divinyl benzene, with tertiary amine and bis-picolylamine functional groups. Our experiment shows that resin XUR-1525 had the greatest loading capacity and most affinity for the molybate ions in the stream, with a concentration of 6500 ppm of molybdenum in its eluant solution after stripping. We conclude that a pH value of 1.7 is the most favorable condition for molybdenum to precipitate as ferrimolybdite. The solution composition and structure of the solids are confirmed by ICP and XRD analyses.