Gas-Phase Deconstruction of UO: Mass Spectrometry Evidence for Generation of [OUCH] by Collision-Induced Dissociation of [UO(C≡CH)].

Because of the high stability and inertness of the U=O bonds, activation and/or functionalization of UO and UO remain challenging tasks. We show here that collision-induced dissociation (CID) of the uranyl-propiolate cation, [UO(OC-C≡CH)], can be used to prepare [UO(C≡CH)] in the gas phase by decarboxylation. Remarkably, CID of [UO(C≡CH)] caused elimination of CO to create [OUCH], thus providing a new example of a well-defined substitution of an "yl" oxo ligand of UO in a unimolecular reaction. Relative energies for candidate structures based on density functional theory calculations suggest that the [OUCH] 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, [OUCH] appears to react spontaneously with O to produce [UO]. Graphical Abstract .