Complexation of rhenium with ethylenediaminetetraacetic acid: Studies of technetium analogue using Raman spectroscopy

摘要

The complexation of rhenium, to the polyaminopolycarboxylate EDTA was investigated using Raman spectroscopy. Complexation occurred when Re ~(VII)O_4 - was placed in the presence of a Sn(II) reducing agent and EDTA. Rhenium complexation was confirmed by the Raman and UV/Vis spectra of the solution samples. Binding modes were assigned using the Raman spectra of a solid-phase sample. Three complexes are proposed, a sixcoordinate dimer H_4[Re_2(μ-O)_2(EDTA)_2], a seven-coordinate monomer H_2[ReO(EDTA)(OH_2)_2] and a mono-oxorhenium [ReO(EDTA)]_~(2-). The solubility of Re(IV)-EDTA complexes is greater than that of ReO_4. If this behaviour is analogous to Tc, it is proposed that complexation to EDTA by Tc(IV) may increase the solubility and enhance the environmental transport of 99Tc from geological repositories.