Extension of the Plutonium Oxide Nanocluster Family to Include {Pu₁₆} and {Pu₂₂}

Abstract

Plutonium(IV) oxide nanoclusters represent an interesting scientific problem regarding structure‐function relationships and are also relevant to global concerns surrounding plutonium reprocessing, the remediation of plutonium‐contaminated soils, and the storage or disposal of plutonium‐containing wastes. Here we report the synthesis of five unique PuIV oxide nanoclusters containing 38, 22, or 16 metal centers and capped only with inorganic ligands, such as chlorine and water, which prevent formation of the extended PuO2 structure. The products are interrogated through single‐crystal X‐ray diffraction, bond valence calculations, and comparisons to other known metal‐oxide nanoclusters. Of particular interest is the incorporation of hydroxide linkages into the smaller plutonium oxide nanoclusters, which underscores previous observations and hypotheses regarding the formation of plutonium polymers and colloids.

Mononuclear to Polynuclear UIV Structural Units: Effects of Reaction Conditions on U‐Furoate Phase Formation

“…Mazzanti and Hixon isolated {An 16 } units for U and Pu, respectively, but these clusters differ significantly from those reported by Loiseau et al. due in part to differences in the U IV coordination environment . Still, it remains unclear how the {U 4 } units isolated in this work relate to these larger oligomers and the {U 38 } cluster, in particular.…”

“…For related Pu 38 clusters, Hixon et al. recently proposed that {Pu 16 } and {Pu 22 } are building blocks for Pu 38 , and gas phase studies by Gibson and Haire show evidence for Pu 6 and Pu 16 species . Consistent with this, Loiseau et al.…”

“…The formation of oligomers has been shown to result from a delicate interplay of hydrolysis and condensation as well as ligand complexation. Recent literature has shown that organic ligands may be used to thwart hydrolysis and condensation, stabilize novel structural units, or otherwise direct the assembly of larger order oligomers from smaller order polynuclear species . As such, the effects of metal/ligand ratios on phase formation were examined.…”

“…The tetravalent state in particular is the most Lewis acidic and thus +4 actinides (An=Th–Pu) are particularly prone to hydrolysis and condensation, with the formation of polynuclear species occurring under even very acidic conditions . Plutonium, for example, has been shown to form large polyoxo clusters ranging from {Pu 16 } to {Pu 38 } oligomers from acidic HCl solutions . Uranium and neptunium similarly form polyoxo clusters; these clusters are often stabilized by organic carboxylates …”

A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles

“…[6][7][8][9][10] Them ost debated question is the structural nature of these NPs (crystalline vs.amorphous) as well as the presence of Pu V and other oxidation states in small NPs (< 3nm). [9,[11][12][13][14][15] Va rious studies used different synthetic approaches and different solution conditions to examine aprecipitated product, either amorphous or crystalline.T his has led to ac ontroversy which has not been resolved. Fore xample,W alther et al [14] observed evidence for multiple Pu oxidation states (III, IV,V )i nt he early stages of hydrolysis and polymerization of PuO 2 colloids at pH 0.5-1.0, while Rothe et al [9] reported Pu IV oxyhydroxide-colloid formation.…”