Plutonium(III) oxalate

Last updated
Plutonium(III) oxalate
Pu2(C2O4)3 9H2O layer.png
Names
IUPAC name
Plutonium(III) oxalate
Identifiers
3D model (JSmol)
  • InChI=1S/3C2H2O4.2Pu/c3*3-1(4)2(5)6;;/h3*(H,3,4)(H,5,6);;/q;;;2*+3/p-6
    Key: PHGVNOKIRFLVGH-UHFFFAOYSA-H
  • C(=O)(C(=O)[O-])[O-].C(=O)(C(=O)[O-])[O-].C(=O)(C(=O)[O-])[O-].[Pu+3].[Pu+3]
Properties
Pu2(C2O4)3
Molar mass 752 g·mol−1
Related compounds
Other anions
Plutonium(III) carbonate
Other cations
Americium(III) oxalate
Curium(III) oxalate
Related plutonium oxalates
 Plutonium(IV) oxalate
Plutonyl oxalate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Plutonium(III) oxalate is a compound consisting of plutonium and oxalate with the formula Pu2(C2O4)3. It is produced by adding oxalic acid to plutonium solution, and is often used as a starting material for other plutonium compounds, like plutonium(IV) oxide, plutonium(III) fluoride, plutonium(III) chloride, or plutonium(III) bromide.

Contents

Synthesis

Upon carefully adding oxalic acid or adding sodium oxalate to an acidic solution containing plutonium(III), often nitric acid, plutonium(III) oxalate hydrates are precipitated. [1] [2] : 836 

Properties

It is a turquoise-blue solid which is quite insoluble, like the related compounds americium(III) oxalate and curium(III) oxalate, and it is easily filterable. [3] [2] : 836  It forms two main hydrates: the decahydrate, Pu2(C2O4)3·10H2O, and the hexahydrate, Pu2(C2O4)3·6H2O. [2] : 1174  Other hydrates are known, such as Pu2(C2O4)3·9H2O, Pu2(C2O4)3·2H2O, and Pu2(C2O4)3·H2O, as well as anhydrous Pu2(C2O4)3 (contains no water). Sources vary as to whether it is the decahydrate, Pu2(C2O4)3·10H2O, or the nonahydrate, Pu2(C2O4)3·9H2O, that is found upon precipitation from aqueous solution. [4] [5]

Decomposition

Data on the thermal decomposition of plutonium(III) oxalate is reported for the nonahydrate. Upon heating, it loses water between 30–225 °C (86–437 °F), going through various different hydrates of compositions Pu2(C2O4)3·8H2O, Pu2(C2O4)3·2H2O, and Pu2(C2O4)3·H2O before reaching anhydrous plutonium(III) oxalate (Pu2(C2O4)3): [6] [7]

Pu2(C2O4)3·9H2O → Pu2(C2O4)3·8H2O + H2O (between 30–80 °C (86–176 °F))
Pu2(C2O4)3·8H2O → Pu2(C2O4)3·2H2O + 6 H2O (between 80–140 °C (176–284 °F))
Pu2(C2O4)3·2H2O → Pu2(C2O4)3·H2O + H2O (between 140–180 °C (284–356 °F))
Pu2(C2O4)3·H2O → Pu2(C2O4)3 + H2O (between 180–225 °C (356–437 °F))

Starting at 225 °C (437 °F), Pu2(C2O4)3 begins to decompose to plutonium dioxide, PuO2, though complete conversion only occurs at 400 °C (752 °F). [6] [7] The intermediates in this process have been studied as part of the thermal decomposition of plutonium(IV) oxalate, which produces anhydrous plutonium(III) oxalate. The transition from Pu2(C2O4)3 to PuO2 goes through several carbonate oxalate phases, with compositions Pu2(C2O4)2CO3 and Pu2C2O4(CO3)2, releasing carbon monoxide, before forming plutonium(IV) oxycarbonate PuOCO3. The compound then finally decomposes to from plutonium dioxide: [8] [9]

Pu2(C2O4)3 → Pu2(C2O4)2CO3 + CO
Pu2(C2O4)2CO3 → Pu2C2O4(CO3)2 + CO
Pu2C2O4(CO3)2 → 2 PuOCO3 + 2 CO
PuOCO3 → PuO2 + CO2
Diagram of the reactions which occur in the thermal decomposition of plutonium(III) oxalate and plutonium(IV) oxalate Decomposition of plutonium oxalates.svg
Diagram of the reactions which occur in the thermal decomposition of plutonium(III) oxalate and plutonium(IV) oxalate

At room temperature in air, plutonium(III) oxalate also decomposes, albeit much more slowly. It eventually degrades to a product proposed to be either a colloidal PuO2 polymer or PuOCO3. [10]

Structure

While the structure of anhydrous plutonium(III) oxalate is unknown, two structures have been predicted by density functional theory (DFT) calculations. One structure consists of plutonium-oxalate layers in a honeycomb-like arrangement, and the other consists of 2D sheets which are connected into a 3D network via bridging oxalate groups. Both of these structures have been calculated to be stable. [8] [11]

On the other hand, the structures of plutonium(III) oxalate nonahydrate (Pu2(C2O4)3·9H2O) and decahydrate (Pu2(C2O4)3·10H2O) are known. Plutonium(III) oxalate decahydrate has been determined to adopt the same structure as lanthanum(III) oxalate decahydrate, La2(C2O4)3·10H2O. [12] Both it and the nonahydrate, Pu2(C2O3)3·9H2O, are made up of repeating honeycomb-like layers of composition Pu2(C2O3)3(H2O)6. Within these layers, each plutonium atom is bonded to nine oxygen atoms, and has a coordination geometry of distorted tricapped trigonal prismatic. Three oxygen atoms come from three water molecules, and six oxygen atoms come from three oxalate groups. Per formula unit, there are either three or four water molecules disjoint from each layer (three for the nonahydrate, four for the decahydrate). [5] [13]

Pu coordination in Pu2(C2O4)3 9H2O.png
Coordination of plutonium in plutonium(III) oxalate nonahydrate. Blue is plutonium, grey is carbon, red is oxygen in oxalate, and sea green is oxygen in water. Hydrogen atoms are omitted.
Pu2(C2O4)3 9H2O layer.png
Single layer of plutonium(III) oxalate nonahydrate. Blue is plutonium, grey is carbon, and red is oxygen. Hydrogen atoms are omitted.

Uses

Plutonium(III) oxalate is frequently used as a starting material for the preparation of other plutonium compounds. [2] : 836–837, 1031–1032, 1077, 1093, 1095  For example, plutonium(IV) oxide is mainly produced by the high-temperature heating of either plutonium(III) oxalate or the related compound plutonium(IV) oxalate. During this process, it is slowly heated up to 700 °C (1,292 °F) to avoid rapid decomposition and evolution of gases, and afterwards it is heated to 1,000 °C (1,830 °F) to remove any carbon left behind. [2] : 1031–1032  For information about the reactions which occur, see above.

Plutonium(III) oxalate can also be used to produce plutonium halides. The compound plutonium(III) fluoride has been prepared at the 150–300 gram scale by heating plutonium(III) oxalate in a stream of hydrogen between 150–600 °C (302–1,112 °F), and then in a stream of hydrogen fluoride between 200–300 °C (392–572 °F): [2] : 1077–1078 

Pu2(C2O4)3 + 6 HF → 2 PuF3 + 3 CO + 3 CO2 + 3 H2O

Plutonium(III) oxalate, in the form of the decahydrate (Pu2(C2O4)3·10H2O), can also be used to prepare plutonium(III) chloride (PuCl3) by reaction with chlorinating agents. Reaction with hydrogen chloride is considered the best method for PuCl3 for medium-scale reactions (between 1 to 10 grams): [2] : 1093 

Pu2(C2O4)3·10H2O + 6 HCl → 2 PuCl3 + 3 CO2 + 3 CO + 13 H2O

Alternatively, the liquid hexachloropropene can be used as a chlorinating agent to avoid working with hazardous gases: [14]

Pu2(C2O4)3·10H2O + 3 C3Cl6 → 2 PuCl3 + 3 C3Cl4O + 3 CO2 + 3 CO + 10 H2O

To prepare plutonium(III) bromide, it can be reacted with hydrogen bromide between 400 °C (752 °F) and 600 °C (1,112 °F). [2] : 1095  Plutonium(III) oxalate can also be used to synthesize various other compounds; e.g. it reacts with rhenium(VII) oxide to produce plutonium(III) perrhenate, Pu(ReO4)3. [2] : 1065 

References

  1. ↑ Kirk-Othmer Encyclopedia of Chemical Technology. Vol. 19. p. 203.
  2. 1 2 3 4 5 6 7 8 9 Clark, David L.; Hecker, Siegfried S.; Jarvinen, Gordon D.; Neu, Mary P. (2011). "Plutonium". The Chemistry of the Actinide and Transactinide Elements (PDF). doi:10.1007/978-94-007-0211-0_7. ISBN   978-94-007-0211-0.
  3. ↑ Burney, G.A.; Porter, J.A. (1967). "Solubilities of Pu(III), Am(III), and Cm(III) oxalates" . Inorganic and Nuclear Chemistry Letters. 3 (3): 79–85. doi:10.1016/0020-1650(67)80128-4.
  4. ↑ Lacount, Michael D.; Meier, David E.; Ritzmann, Andrew M.; Muller, Scott E.; Clark, Richard A.; Buck, Edgar C.; Abrecht, David G. (2023). "Ab initio modeling and thermodynamics of hydrated plutonium oxalates". Journal of Nuclear Materials. 583 154504. Bibcode:2023JNuM..58354504L. doi:10.1016/j.jnucmat.2023.154504. OSTI   1988226.
  5. 1 2 Runde, Wolfgang; Brodnax, Lia F.; Goff, George; Bean, Amanda C.; Scott, Brian L. (2009). "Directed Synthesis of Crystalline Plutonium(III) and (IV) Oxalates: Accessing Redox-Controlled Separations in Acidic Solutions" (PDF). Inorganic Chemistry. 48 (13): 5967–5972. doi:10.1021/ic900344u. OSTI   956410. PMID   19485387.
  6. 1 2 Christian, Jonathan H.; Foley, Bryan J.; Ciprian, Elodia; Darvin, Jason; Dick, Don D.; Hixon, Amy E.; Villa-Aleman, Eliel (2023). "Probing the thermal decomposition of plutonium (III) oxalate with IR and Raman spectroscopy, X-ray diffraction, and electron microscopy". Journal of Nuclear Materials. 584 154596. Bibcode:2023JNuM..58454596C. doi:10.1016/j.jnucmat.2023.154596. OSTI   1993013.
  7. 1 2 De Almeida, Lucie; Grandjean, Stephane; Vigier, Nicolas; Patisson, Fabrice (2012). "Insights into the Thermal Decomposition of Lanthanide(III) and Actinide(III) Oxalates – from Neodymium and Cerium to Plutonium". European Journal of Inorganic Chemistry (31): 4986–4999. arXiv: 1402.3046 . Bibcode:2012EJIC.2012.4986D. doi:10.1002/ejic.201200469.
  8. 1 2 South, Christopher J.; Roy, Lindsay E. (2021). "Insights into the thermal decomposition of plutonium(IV) oxalate – a DFT study of the intermediate structures". Journal of Nuclear Materials. 549 152864. Bibcode:2021JNuM..54952864S. doi:10.1016/j.jnucmat.2021.152864. OSTI   1805215.
  9. ↑ Orr, R.M.; Sims, H.E.; Taylor, R.J. (2015). "A review of plutonium oxalate decomposition reactions and effects of decomposition temperature on the surface area of the plutonium dioxide product" . Journal of Nuclear Materials. 465: 756–773. Bibcode:2015JNuM..465..756O. doi:10.1016/j.jnucmat.2015.06.058.
  10. ↑ Corbey, Jordan F.; Sweet, Lucas E.; Sinkov, Sergey I.; Reilly, Dallas D.; Parker, Cyrena M.; Lonergan, Jason M.; Johnson, Timothy J. (2021). "Quantitative Microstructural Characterization of Plutonium Oxalate Auto-Degradation and Evidence for PuO2 Nanocrystal Formation". European Journal of Inorganic Chemistry (32): 3277–3291. Bibcode:2021EJIC.2021.3277C. doi:10.1002/ejic.202100511. OSTI   1808901.
  11. ↑ Isbill, Sara B.; Miskowiec, Andrew J. (2025). "Computational insights into the structure of anhydrous Pu(III) oxalate". Journal of Nuclear Materials. 605 155583. Bibcode:2025JNuM..60555583I. doi:10.1016/j.jnucmat.2024.155583. OSTI   2491455.
  12. ↑ Chackraburtty, D. M. (1963). "X-ray evidence of plutonium(III) oxalate decahydrate" . Acta Crystallographica. 16 (8): 834. Bibcode:1963AcCry..16..834C. doi:10.1107/S0365110X63002127.
  13. ↑ Uríková, Daniela Veronika; Kampitakis, Giannis; Císařová, Ivana; Alemayehu, Adam; Kloda, Matouš; Zákutná, Dominika; Lang, Kamil; Demel, Jan; Tyrpekl, Václav (2025). "Lanthanide Oxalates: From Single Crystals to 2D Functional Honeycomb Nanosheets". Inorganic Chemistry. 64 (8): 3686–3695. doi:10.1021/acs.inorgchem.4c04293. PMC   11881034 . PMID   39964120.
  14. ↑ "Preview" (PDF).
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