ThePuCl2−6 ion features a slightly distortedoctahedral molecular geometry, with three distinct Pu-Cl bonds. The Pu-Clbond lengths vary between 2.574 and 2.598 Å, and the Cl-Pu-Clbond angles range between 88.54° and 91.46°.[3]
The Pu-Cl bonds inPuCl2−6 are primarilyionic; however, they feature small but important amounts ofcovalent bonding. Thechlorideligands bond using theirs andp electrons, while plutonium bonds using its s,d, andf electrons. The Pu-Clbond order is less than 1, and the shape of the Pu-Cl bond slightly deviates fromcylindrical, possibly indicating a small amount ofpi bonding.[3] The 5f electrons in thePuCl2−6 have a largenephelauxetic effect[4] (decrease in electron-electron repulsion).
ThePuCl2−6 ion forms severalsalts.Dicaesium hexachloroplutonate (Cs2PuCl6) is a pale yellow solid which is precipitated from concentrated HCl solution by the addition ofcaesium chloride.Cs2PuCl6 can be used to prepare other plutonium compounds, such as thecyclopentadienide 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 aprimary standard for plutonium.[2]: 839, 1104, 1191 [5]Potassium andrubidium hexachloroplutonates,K2PuCl6 andRb2PuCl6, are also known. They are prepared by heating mixtures ofplutonium(III) chloride and the respective alkali metalchlorides under high chlorine pressures.[6]
^abWang, 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.
