Hexachloroplutonate

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Hexachloroplutonate
The hexachloroplutonate dianion
Identifiers
3D model (JSmol)
  • InChI=1S/6ClH.Pu/h6*1H;/q;;;;;;+4/p-6
    Key: QYJYVEJBCPQDNB-UHFFFAOYSA-H
  • Cl[Pu-2](Cl)(Cl)(Cl)(Cl)Cl
Properties
PuCl2−6
Molar mass 457 g·mol−1
Related compounds
Other anions
 Hexafluoroplutonate
Other cations
 Hexachloroplatinate; Hexachloropalladate; Hexachlorogermanate(IV)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

The hexachloroplutonate ion, PuCl2−6, is an ion containing plutonium and chlorine. It forms several salts, which are called hexachloroplutonates.[1][2]: 1104 

Structure and bonding

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The PuCl2−6 ion features a slightly distorted octahedral molecular geometry, with three distinct Pu-Cl bonds. The Pu-Cl bond lengths vary between 2.574 to 2.598 Å, and the Cl-Pu-Cl bond angles range between 88.54° to 91.46°.[3]

The Pu-Cl bonds in PuCl2−6 are primarily ionic; however, they feature small but important amounts of covalent bonding. The chloride ligands bond using their s and p electrons, while plutonium bonds using its s, d, and f electrons. The Pu-Cl bond order is less than 1, and the shape of the Pu-Cl bond slightly deviates from cylindrical, possibly indicating a small amount of pi bonding.[3] The 5f electrons in the PuCl2−6 have a large nephelauxetic effect[4] (decrease in electron-electron repulsion).

In aqueous solution

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It is the dominant species of plutonium(IV) in 11 M hydrochloric acid solution.[5]

Salts

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The PuCl2−6 ion forms several salts. Dicaesium hexachloroplutonate (Cs2PuCl6) is a pale yellow solid which is precipitated from concentrated HCl solution by the addition of caesium chloride. Cs2PuCl6 can be used to prepare other plutonium compounds, such as the cyclopentadienide complex (η5-C5H5)3PuCl, and it has been proposed for use in the purification of plutonium metal. It has been used as a reference for plutonium(IV), and due to its stability, it has been proposed for use as a primary standard for plutonium.[2]: 839, 1104, 1191 [5] Potassium and rubidium hexachloroplutonates, K2PuCl6 and Rb2PuCl6, are also known. They are prepared by heating mixtures of plutonium(III) chloride and the respective alkali metal chlorides under high chlorine pressures.[6]

PuCl2−6 is also known to form salts with quaternary ammonium cations, including tetramethylammonium, tetraethylammonium,[2]: 1104  and tetrabutylammonium.[7] The tetramethylammonium and tetraethylammonium salts, [NMe4]2[PuCl6] and [NEt4]2[PuCl6], form orange-yellow crystals.[2]: 1109  [NEt4]2[PuCl6] was used in the first synthesis of plutonocene.[8] The tetrabutylammonium salt, [N(n-Bu)4]2[PuCl6], is prepared by the addition of tetrabutylammonium chloride to plutonium(IV) in HCl aqueous solution. It is soluble in several organic solvents.[7]

PuCl2−6 is also known to form salts with pyridinium, pyridinium dervatives,[3][9] and tetraphenylphosphonium.[10]

References

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  1. ^ Wilson, Richard E. (2015). "Structure, Phase Transitions, and Isotope Effects in [(CH3)4N]2PuCl6". Inorganic Chemistry. 54 (21): 10208–10213. doi:10.1021/acs.inorgchem.5b01288. PMID 26225472.
  2. ^ a b c d 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. ^ a b c Surbella, Robert G.; Ducati, Lucas C.; Schofield, Mark H.; McNamara, Bruce K.; Pellegrini, Kristi L.; Corbey, Jordan F.; Schwantes, Jon M.; Autschbach, Jochen; Cahill, Christopher L. (2022). "Plutonium Hybrid Materials: A Platform to Explore Assembly and Metal–Ligand Bonding". Inorganic Chemistry. 61 (45): 17963–17971. doi:10.1021/acs.inorgchem.2c02084. OSTI 1957814. PMID 36305869. (Supporting information: https://pubs.acs.org/doi/suppl/10.1021/acs.inorgchem.2c02084/suppl_file/ic2c02084_si_001.pdf)
  4. ^ Ryan, J.L.; Jørgensen, Chr. Klixbüll (1964). "Electron transfer and 5f→6f transitions in uranium(IV), neptunium(IV), plutonium(IV) hexahalides". Molecular Physics. 7 (1): 17–29. Bibcode:1964MolPh...7...17R. doi:10.1080/00268976300100781.
  5. ^ 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.
  6. ^ Morss, Lester R.; Fujino, Takeo (1988). "Preparation and crystal structures of plutonium(IV) hexachloro complexes, Rb2PuCl6 and K2PuCl6". Journal of Solid State Chemistry. 72 (2): 338–352. doi:10.1016/0022-4596(88)90038-2.
  7. ^ a b Reilly, Sean D.; Scott, Brian L.; Gaunt, Andrew J. (2012). "[N(n-Bu)4]2[Pu(NO3)6] and [N(n-Bu)4]2[PuCl6]: Starting Materials to Facilitate Nonaqueous Plutonium(IV) Chemistry". Inorganic Chemistry. 51 (17): 9165–9167. doi:10.1021/ic301518g. PMID 22900742.
  8. ^ Karraker, David G.; Stone, John Austin; Jones, Erwin Rudolph; Edelstein, Norman (1970-08-01). "Bis(cyclooctatetraenyl)neptunium(IV) and bis(cyclooctatetraenyl)plutonium(IV)". Journal of the American Chemical Society. 92 (16): 4841–4845. Bibcode:1970JAChS..92.4841K. doi:10.1021/ja00719a014. ISSN 0002-7863.
  9. ^ Wilson, Richard E.; Schnaars, David D.; Andrews, Michael B.; Cahill, C. L. (2014). "Supramolecular Interactions in PuO2Cl42– and PuCl62– Complexes with Protonated Pyridines: Synthesis, Crystal Structures, and Raman Spectroscopy". Inorganic Chemistry. 53 (1): 383–392. doi:10.1021/ic4023294. PMID 24328217.
  10. ^ Minasian, Stefan G.; Boland, Kevin S.; Feller, Russell K.; Gaunt, Andrew J.; Kozimor, Stosh A.; May, Iain; Reilly, Sean D.; Scott, Brian L.; Shuh, David K. (2012). "Synthesis and Structure of (Ph4P)2MCL6(M = Ti, Zr, Hf, Th, U, Np, Pu)". Inorganic Chemistry. 51 (10): 5728–5736. doi:10.1021/ic300179d. PMID 22554112.