Creation of [OUF]+ using gas-phase reactions of [UO2(C6F5)]+

While the strong axial U=O bonds confer high stability and inertness to UO22+, it has been shown that the axial oxo ligands can be eliminated or replaced in the gas-phase using collision-induced dissociation (CID) reactions. In this study, CID of the pentafluorobenzoate precursor ion [UO2(O2C-C6F5)](+) was used to produce the organo-uranyl ion [UO2(C6F5)](+) by decarboxylation. Subsequent CID of [UO2(C6F5)](+) created [UO2(F)](+) by fluoride transfer and elimination of C6F4, rather than UO2+ by elimination of pentafluorophenyl radical (as has been observed for similar species). Moreover, upon reaction of [UO2(C6F5)](+) with H2O, apparent substitution of OH for F to create [UO3HC6F4](+) is favored over hydrolysis to produce [UO2(OH)](+) and (neutral) C6F5H. Subsequent CID of [UO3HC6F4](+) generates [UO2(F)](+) and [OUF](+). When [OUF](+) is isolated to react with H2O and O-2 in the ion trap, the principal product ions observed are [UO2(F)](+) and [UO2(OH)](+). Experiments conducted with labeled reagent suggest that reaction with (H2O)-O-18 leads to exchange of the oxo ligand and incorporation of the O-18 label into [OUF](+) while reaction with O-2 likely creates [UO2(F)](+). Formation of [UO2(OH)](+) from [OUF](+) is the result of a cascade of reactions, with initial formation of [UO2(F)](+) by reaction with O-2, followed by hydrolysis to create the hydroxide species. (C) 2021 Elsevier B.V. All rights reserved.