Dicaesium hexachloroplutonate
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3D model (JSmol)
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| Properties | |||
| Cs2PuCl6 | |||
| Molar mass | 723 g·mol−1 | ||
| Density | 4.10 g/cm3 | ||
| Solubility | Soluble in dilute acids[2] | ||
| Related compounds | |||
Other anions
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Caesium hexachloroplatinate | ||
Other cations
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Tetramethylammonium hexachloroplutonate(IV) | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Dicaesium hexachloroplutonate (or DCHP)[1] is a compound of caesium, plutonium, and chlorine with formula Cs2PuCl6. It has been used in the synthesis of other plutonium compounds,[3]: 1184, 1190–1191 and in the purification of plutonium metal.[1]
Synthesis
[edit]DCHP is prepared by first suspending a plutonium sample in water. Then, concentrated hydrochloric acid is added to the mixture. To ensure that all the plutonium is in the +4 oxidation state, an aqueous solution containing sodium chlorite is mixed in with the plutonium solution. Immediately upon adding caesium chloride solution, Cs2PuCl6 is precipitated, and is left to sit for 12 hours. The Cs2PuCl6 powder is then isolated by vacuum filtration, washed with concentrated HCl, and then left to dry for 8 hours at 120 °C in an oven.[4]
Properties
[edit]Dicaesium hexachloroplutonate forms pale yellow crystals[3]: 1109 which adopt the K2GeF6-type structure, forming trigonal crystals. Each plutonium atom is bonded to six chlorine atoms as discrete hexachloroplutonate anions (PuCl2−6), and each caesium atom is bonded to twelve chlorine atoms. The hexachloroplutonate ion has octahedral molecular geometry, and in DCHP, the Pu-Cl bond length is 2.62 Å. The Cs-Cl bonds have a length of 3.71 Å.[3]: 1190 [5]
DCHP is a stoichiometric compound, and unlike other plutonium compounds, such as plutonium(IV) nitrate, DCHP is non-hygroscopic.[2]
Reactions
[edit]Dicaesium hexachloroplutonate can undergo several reactions, and as such, it is used to prepare other plutonium compounds. For example, upon reaction with cyclopentadienylthallium in acetonitrile solution, it forms the coordination complex (η5-C5H5)3PuCl:
It also reacts with magnesium cyclopentadienide in tetrahydrofuran to give an emerald green product, most likely (η5-C5H5)3Pu(THF) (THF=tetrahydrofuran), which loses its tetrahydrofuran ligand upon sublimation to form (η5-C5H5)3Pu. Plutonium(III) chloride, PuCl3, also reacts with magnesium cyclopentadienide, though the reaction occurs much more slowly, likely because PuCl3 has a polymeric structure while Cs2PuCl6 contains discrete PuCl2−6 groups.[3]: 1190–1191
Dicaesium hexachloroplutonate can also be used to synthesize plutonium tetrachloride adducts. Upon reaction with amides or phosphine oxides, it forms the adducts PuCl4L2 or PuCl4L3 (L=amide or phosphine oxide).[3]: 1184
Dicaesium hexachloroplutonate reacts with ammonia to form the complex PuCl4·~7–8NH3. It is an ammine complex, meaning the ammonia groups are bonded to the plutonium atom. The complex decomposes over time to give the solid PuCl4·~5NH3, which is stable at room temperature.[6]
Uses
[edit]As a standard
[edit]Because of several of its properties, such as its non-hygroscopicity, high equivalent weight, and an absence of non-stoichiometry, it has been proposed for use as a plutonium primary standard. It has been used as a reference for plutonium in its +4 oxidation state.[2][4]
In plutonium separation
[edit]Before it shut down, DCHP was used at Rocky Flats Plant in the separation of americium from plutonium metal. It was used as an oxidant to oxidize plutonium metal to plutonium(III) chloride in a molten calcium chloride matrix. Any americium would then react with plutonium(III) chloride and be extracted into the calcium chloride matrix.[1]
References
[edit]- ^ a b c d https://www.osti.gov/servlets/purl/6107759
- ^ a b c d Miner, F. J.; Degrazio, R. P.; Byrne, J. T. (1963). "Dicesium Plutonium Hexachloride, a Proposed Primary Standard for Plutonium". Analytical Chemistry. 35 (9): 1218–1223. doi:10.1021/ac60202a003.
- ^ a b c d e 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.
- ^ a b Wang, Yufei; Rice, Natalie T.; Knapp, Julia G.; Adelman, Sara L.; Aldrich, Kelly E.; Arko, Brian T.; Besmer, Manuel L.; Gilhula, J. Connor; Godt, Christopher J.; Klouda, Jan; Kozimor, Stosh A.; Long, Brian N.; MacInnes, Molly M.; Marshall-Roth, Travis; Nagelski, Alexandra L.; Piedmonte, Ida D. (2025). "Insights for controlling plutonium behavior in hydrochloric acid solutions". Inorganic Chemistry Frontiers. 12 (14): 4392–4408. doi:10.1039/D5QI00409H.
- ^ Zachariasen, W. H. (1948). "Crystal chemical studies of the 5f-series of elements. II. The crystal structure of Cs2PuCl6". Acta Crystallographica. 1 (5): 268–269. Bibcode:1948AcCry...1..268Z. doi:10.1107/S0365110X48000715.
- ^ Cleveland, J.M.; Bryan, G.H.; Sironen, R.J. (1972). "Ammoniates of plutonium(III) and (IV) halides". Inorganica Chimica Acta. 6: 54–58. doi:10.1016/S0020-1693(00)91758-4.