Gas-Phase Reactions of Molecular Oxygen with Uranyl(V) Anionic Complexes—Synthesis and Characterization of New Superoxides of Uranyl(VI)

Abstract

Gas-phase complexes of uranyl(V) ligated to anions X(-) (X = F, Cl, Br, I, OH, NO3, ClO4, HCO2, CH3CO2, CF3CO2, CH3COS, NCS, N3), [UO2X2](-), were produced by electrospray ionization and reacted with O2 in a quadrupole ion trap mass spectrometer to form uranyl(VI) anionic complexes, [UO2X2(O2)](-), comprising a superoxo ligand. The comparative rates for the oxidation reactions were measured, ranging from relatively fast [UO2(OH)2](-) to slow [UO2I2](-). The reaction rates of [UO2X2](-) ions containing polyatomic ligands were significantly faster than those containing the monatomic halogens, which can be attributed to the greater number of vibrational degrees of freedom in the polyatomic ligands to dissipate the energy of the initial O2-association complexes. The effect of the basicity of the X(-) ligands was also apparent in the relative rates for O2 addition, with a general correlation between increasing ligand basicity and O2-addition efficiency for polyatomic ligands. Collision-induced dissociation of the superoxo complexes showed in all cases loss of O2 to form the [UO2X2](-) anions, indicating weaker binding of the O2(-) ligand compared to the X(-) ligands. Density functional theory computations of the structures and energetics of selected species are in accord with the experimental observations.

Formation and hydrolysis of gas‐phase [UO2(R)]+: R═CH3, CH2CH3, CH═CH2, and C6H5

“…When cooled, 20 μL of the resulting solution was diluted with 800 μL of 50:50 (by volume) H 2 O:CH 3 CH 2 OH and used without further work up as the spray solution for ESI‐MS. CH 3 CH 2 OH is used as co‐solvent in most of our experiments to avoid any ambiguity when looking for potential molecular O 2 adducts to product ions . With the limited mass measurement accuracy of the LIT, O 2 and CH 3 OH adducts cannot be distinguished.…”

Heptavalent Actinide Tetroxides NpO4– and PuO4–: Oxidation of Pu(V) to Pu(VII) by Adding an Electron to PuO4

“…Although the isotopic purity of the 18 O 2 was unknown, the relative pressure of 18 O 2 and 16 O 2 was determined by monitoring the previously reported reaction of UO 2 (CH 3 CO 2 ) 2 − with O 2 to yield UO 2 (O 2 )(CH 3 CO 2 ) 2 − . 27…”

Gas Phase Reactions of Ions Derived from Anionic Uranyl Formate and Uranyl Acetate Complexes

“…When cooled, 20 μL of the resulting solution was diluted with 800 μL of 50:50 (by volume) H 2 O/EtOH and used without further work-up as the spray solution for ESI-MS. Ethanol was used for these experiments to avoid any ambiguity when looking for potential molecular O 2 adducts to product ions [32][33][34][35]. With the limited mass measurement accuracy of the LIT, O 2 and CH 3 OH adducts cannot be distinguished.…”