Gas-Phase Coordination Complexes of U^VIO₂²⁺, Np^VIO₂²⁺, and Pu^VIO₂²⁺ with Dimethylformamide

Abstract

Abstract, where An = U, Np, and Pu. Collision-induced dissociation confirmed the composition of the dipositive coordination complexes, and produced doubly-and singly-charged fragment ions. The fragmentation products reveal differences in underlying chemistries of uranyl, neptunyl, and plutonyl, including the lower stability of Np(VI) and Pu(VI) compared with U(VI).

Roles of Acetone and Diacetone Alcohol in Coordination and Dissociation Reactions of Uranyl Complexes

“…This work describes an integrated experimental and computational effort to study the role of acetone and diacetone alcohol molecules in uranyl coordination and dissociation reactions. The work presented here, which was proposed in the previous experimental report, 4 provides a detailed picture of the composition and water-elimination reactions observed in the poorly understood "[UO 2 -(ACO) 6,7,8 ] 2+ " species previously identified and disputes any speculation on the possibility of unusually high coordination numbers in gas-phase uranyl acetone coordination complexes. 4 None of the essential conclusions in ref 4 U) was performed in a radiological laboratory.…”

“…Water elimination reactions of diacetone alcohol ligands are shown to have two coordination-dependent reaction channels, through formation of mesityl oxide ligands or formation of alkoxide and protonated mesityl oxide species. The present results provide an explanation for the implausible observation of "[UO 2 (ACO) 6,7,8 ] 2+ " in and observed water-elimination reactions from purportedly uranyl− acetone complexes (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem.…”

“…Figure 2b and [UO 2 (DAA)- 8 ] 2+ " were even more problematic. 4 With the knowledge that DAA was present in other complexes, we speculated that DAA ligands also accounted for these complexes.…”

“…Recent mass spectrometry experiments by some of us were performed with the successful primary goal of producing the first gas-phase dipositive plutonyl complexes. 4 In that work, ESI of uranyl acetone solutions produced species with m/z ratios of 309, 338, and 367 for which there was no apparent explanation other than implausible "hypercoordinated" "[UO 2 (ACO) 6,7,8 ] 2+ " complexes. 4 Subsequent computational studies definitively showed that a first coordination shell (or inner sphere) with more than six acetones was energetically not feasible and that this explanation was incorrect.…”

“…ESI and ion−molecule reactions were studied using an Agilent 6340 Quadrupole Ion Trap Mass Spectrometer (QIT/MS) with the ion source located inside of a radiological containment glovebox, as described in detail elsewhere. 4,8 The sequential multistage mass spectrometry (MS n ) collision-induced dissociation (CID) capabilities of the QIT/MS allow for isolation of ions with a particular mass-to-charge ratio, m/z, followed by resonant variable-energy excitation, which results in multiple energetic collisions of the selected ion with the He bath gas and ultimately in ion decomposition/ fragmentation by one or more pathways. CID fragmentation products are determined by mass-selective ion ejection from the trap into an electron multiplier detector.…”