Destruction and reconstruction of UO using gas-phase reactions

Michael J. Van Stipdonk, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Ave., 308 Mellon Hall, Pittsburgh, PA 15282, USA. vanstipdonkm@duq.edu.
Evan H. Perez, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Ave., 308 Mellon Hall, Pittsburgh, PA 15282, USA. vanstipdonkm@duq.edu.
Luke J. Metzler, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Ave., 308 Mellon Hall, Pittsburgh, PA 15282, USA. vanstipdonkm@duq.edu.
Amanda R. Bubas, Department of Chemistry and Biochemistry, Duquesne University, 600 Forbes Ave., 308 Mellon Hall, Pittsburgh, PA 15282, USA. vanstipdonkm@duq.edu.
Theodore Corcovilos, Department of Physics, Duquesne University, Pittsburgh, PA 15282, USA. corcovilost@duq.edu.
Arpad Somogyi, Campus Chemical Instrument Center, The Ohio State University, Columbus, OH 43210, USA.

Abstract

While the strong axial U[double bond, length as m-dash]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. We report here tandem mass spectrometry experiments initiated with a gas-phase complex that includes UO22+ coordinated by a 2,6-difluorobenzoate ligand. After decarboxylation to form a difluorophenide coordinated uranyl ion, [UO2(C6F2H3)]+, CID causes elimination of CO, and then CO and C2H2 in sequential dissociation steps, to leave a reactive uranium fluoride ion, [UF2(C2H)]+. Reaction of [UF2(C2H)]+ with CH3OH creates [UF2(OCH3)]+, [UF(OCH3)2]+ and [UF(OCH3)2(CH3OH)]+. Cleavage of C-O bonds within these species results in the elimination of methyl cation (CH3+). Subsequent CID steps convert [UF(OCH3)2]+ to [UO2(F)]+ and similarly, [U(OCH3)3]+ to [UO2(OCH3)]+. Our experiments show removal of both uranyl oxo ligands in "top-down" CID reactions and replacement in "bottom-up" ion-molecule and dissociation steps.