Creation of Gas-Phase Organo-Uranium Species by Removal of "yl" Oxo Ligands From UO2 2+ Carboxylate Precursor Ions.

Abstract

These experiments were conducted to measure the diversity of organo-U (IV) and U (III) ions created using multiple-stage tandem MS and collision-induced dissociation of halogen-substituted UVIO2-phenide complexes [UO2(C6H3FX)]+, X = Cl, Br, or I. Samples of UO2(O2C-C6H3FX)2 were prepared by digesting UO3 with appropriate halogen-substituted carboxylic acids in deionized water. Solutions for ESI were created by diluting the digested sample in 50:50 H2O/CH3OH. Precursor ions for multiple-stage tandem MS were generated by electrospray ionization (ESI). Multiple-stage collision-induced dissociation (He collision gas) in a linear quadrupole ion trap mass spectrometer was used to prepare species such as [UIVFX(C≡CH)]+ and UIIIF(C≡CH)]+ for subsequent study of ion-molecule reactions with adventitious neutrals in the ion trap. Multiple-stage CID of the [UO2(C6H3FX)]+, X = Cl, Br, or I, complexes caused removal of both "yl" oxo ligands from of the UO2 2+ moiety to create ions such as [UIVFX(C≡CH)]+ and [UIIIFX]+. For [UIVFXC≡CH]+ and [UIIIFC≡CH]+ products, hydrolysis to generate [UIVFX (OH)]+ and [UIIIF (OH)]+, with concomitant loss of HC≡CH, was observed. CID of [UO2(C6H3FBr)]+ and [UO2(C6H3FI)]+ caused reductive elimination of the respective halogen radicals to generate interesting organo-U (III) species such as [UIIIF(C≡CH)]+ and [UIIIC2]+. The use of "preparative" tandem mass spectrometry and a suite of halogen substituted benzoic acid ligands can be used to remove both oxo ligands of UO2 2+ and generate a group of homologous organo-U (IV) and organo-U (III) ions for studies of intrinsic reactivity.