Síntese e caracterização de complexos de rênio e tecnécio contendo ligantes arilcalcogenolatos (Se, Te)

Abstract

Rhenium and technetium coordination chemistry containing arylthiolate ligands are long known in the literature. However, there is a limited understanding regarding the correlates containing heavier chalcogens (Se and Te), which is primarily due to the instability of the ArEH species. In order to improve the state of the art of this field, this thesis presents a study concerning the coordination chemistry of the elements rhenium and technetium with arylchalcogenolate ligands (Se,Te). The applied methodology involves the production of the ligands in situ, by the reduction of the diaryldichalcogenides with LiBH4 solution, resulting in the formation of lithium arylchalcogenolates (LiEAr). Halide substitution reactions with metals in different oxidation states, containing several ancillary ligands, resulted in 16 new complexes with fair yields, in the range of 51% to 74%. Although the complexes are stable in solid state, they exhibit moderate to high decomposition when in solution. Among the obtained results, two classes are highlighted, the first complexes featuring the Tc–Te bond and the first arylselenolate Tc complexes. Since methods of crystallization employed were successful, X-ray diffraction was used as main characterization method, revealing the coordination environment of the complexes. Additional analysis such as infrared spectroscopy, nuclear magnetic resonance and mass spectroscopy confirm the obtained results. Due to the nature of the technetium compounds, DFT (Density Functional Theory) calculations were performed, unveiling details of the bonding structure in such compounds. From the positive outcome of the employed methodology, with assorted examples, this study paves the way for future research, either with more sophisticated arylchalcogenolate ligands, having additional coordination sites, as well the use of additional classes of rhenium and technetium complexes.