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Insight into the structural ambiguity of actinide(IV) oxalate sheet structures: a case for alternate coordination geometries

Journal Article · · Chemistry - A European Journal (Online)
 [1];  [2];  [1];  [3];  [1];  [1];  [1];  [1];  [3];  [1];  [1]
  1. University of Notre Dame, IN (United States)
  2. University of Notre Dame
  3. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
+ Show Author Affiliations
Plutonium(IV) oxalate hexahydrate (Pu(C2O4)2 ∙ 6H2O; PuOx) is an important intermediate in the recovery of plutonium from used nuclear fuel. Its formation via precipitation is well studied, yet its crystal structure remains unknown. Instead, the crystal structure of PuOx is assumed to be isostructural with neptunium(IV) oxalate hexahydrate (Np(C2O4)­2 ∙ 6H2O; NpOx) and uranium(IV) oxalate hexahydrate (U(C2O4)­2 ∙ 6H2O; UOx) despite the high degree of unresolved disorder that exists when determining water positions in the crystal structures of the latter two compounds. Such assumptions regarding the isostructural behavior of the actinide elements have been used to predict the structure of PuOx for use in a wide range of studies. Herein, we report the first crystal structures for PuOx and Th(C2O4)2 · 6H2O (ThOx). This data, along with new characterization of UOx and NpOx, has resulted in the full determination of the structures and resolution of the disorder around the water molecules. Specifically, we identify the coordination of two water molecules with each metal center, which necessitates a change in oxalate coordination mode from axial to equatorial that has not been reported in the literature. Here this work exemplifies the need to revisit previous assumptions regarding fundamental actinide chemistry, which are heavily relied upon within the current nuclear field.
Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); University of Notre Dame, IN (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
89233218CNA000001; AC05-00OR22725; NA0003763; SC0018231
OSTI ID:
1983863
Alternate ID(s):
OSTI ID: 1988690
OSTI ID: 1989665
OSTI ID: 2283878
Report Number(s):
LA-UR-23-23725
Journal Information:
Chemistry - A European Journal (Online), Journal Name: Chemistry - A European Journal (Online) Journal Issue: 47 Vol. 29; ISSN 1521-3765
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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