PuIV

Pu(IV) refers to plutonium in the +4 oxidation state, commonly written as Pu4+. In aqueous solution, Pu4+ is highly charge dense and undergoes hydrolysis, forming a series of hydroxo species and often aging into polymeric complexes or insoluble solids such as Pu(OH)4 as pH increases. In strongly acidic media, solvated Pu4+ species prevail, while at higher pH the chemistry shifts toward hydrolyzed and precipitated forms.

In coordination chemistry, Pu(IV) forms a variety of complexes with ligands such as fluoride, oxalate, citrate, carbonate, and phosphate. Fluoride coordination can stabilize Pu(IV) species and alter their solubility, whereas carbonate and other ligands can promote mixed hydroxo–carbonate complexes that affect mobility in solution. Pu(IV) also participates in solid-state chemistry, where it occurs in oxide and salt forms, including PuO2, a fluorite-structured solid, and PuF4, among other compounds.

Redox behavior is an important aspect of Pu(IV) chemistry. Pu4+ can be oxidized to Pu(V) or Pu(VI) under oxidative conditions, though Pu(IV) is relatively more stable than Pu(III) in many environments. In nuclear fuel reprocessing and related technologies, maintaining plutonium in the +4 state is a feature of certain separation schemes, while reductants can be used to convert higher oxidation states back to Pu(IV).

Safety and handling: Pu(IV) compounds are highly radiotoxic alpha emitters. They require specialized facilities, strict containment, and regulatory controls to minimize inhalation, ingestion, and environmental release risks.