Gas-Phase Deconstruction of UO22+: Mass Spectrometry Evidence for Generation of [OUVICH]+ by Collision-Induced Dissociation of [UVIO2(C≡CH)]

Abstract

Because of the high stability and inertness of the U=O bonds, activation and/or functionalization of UO₂²⁺ and UO₂⁺ remain challenging tasks. We show here that collision-induced dissociation (CID) of the uranyl-propiolate cation, [U^VIO₂(O₂C-C≡CH)]⁺, can be used to prepare [U^VIO₂(C≡CH)]⁺ in the gas phase by decarboxylation. Remarkably, CID of [U^VIO₂(C≡CH)]⁺ caused elimination of CO to create [OU^VICH]⁺, thus providing a new example of a well-defined substitution of an "yl" oxo ligand of U^VIO₂²⁺ in a unimolecular reaction. Relative energies for candidate structures based on density functional theory calculations suggest that the [OU^VICH]⁺ ion is a uranium-methylidyne product, with a U≡C triple bond composed of one σ-bond with contributions from the U df and C sp hybrid orbitals, and two π-bonds with contributions from the U df and C p orbitals. Upon isolation, without imposed collisional activation, [OU^VICH]⁺ appears to react spontaneously with O₂ to produce [U^VO₂]⁺. Graphical Abstract .

Keywords: Collision-induced dissociation; Density functional theory; Ion trap mass spectrometry; Oxo ligand substitution; Uranyl ion.