Gas-phase synthesis of [OU-X]+ (X = Cl, Br and I) from a UO22+ precursor using ion-molecule reactions and an [OUCH]+ intermediate

Abstract

Difficulty in the preparation of gas-phase ions that include U in middle oxidation states(III,IV) have hampered efforts to investigate intrinsic structure, bonding and reactivity of model species. Our group has used preparative tandem mass spectrometry (PTMS) to synthesize a gas-phase U-methylidyne species, [OUCH]⁺, by elimination of CO from [UO₂(CCH)]⁺ [M. J. van Stipdonk, I. J. Tatosian, A. C. Iacovino, A. R. Bubas, L. Metzler, M. C. Sherman and A. Somogyi, J. Am. Soc. Mass Spectrom., 2019, 30, 796-805], which has been used as an intermediate to create products such as [OUN]⁺ and [OUS]⁺ by ion-molecule reactions. Here, we investigated the reactions of [OUCH]⁺ with a range of alkyl halides to determine whether the methylidyne is a also a useful intermediate for production and study of the oxy-halide ions [OUX]⁺, where X = Cl, Br and I, formally U(IV) species for which intrinsic reactivity data is relatively scarce. Our experiments demonstrate that [OUX]⁺ is the dominant product ion generated by reaction [OUCH]⁺ with neutral regents such as CH₃Cl, CH₃CH₂Br and CH₂CHCH₂I.