Two Dihydroxo-Bridged Plutonium(IV) Nitrate Dimers
and Their Relevance to Trends in Tetravalent Ion Hydrolysis and Condensation
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Abstract
We report the room temperature synthesis
and structural characterization of a μ<sub>2</sub>-hydroxo-bridged
Pu<sup>IV</sup> dimer obtained from an acidic nitric acid solution.
The discrete Pu<sub>2</sub>(OH)<sub>2</sub>(NO<sub>3</sub>)<sub>6</sub>(H<sub>2</sub>O)<sub>4</sub> moiety crystallized with two distinct
crystal structures, [Pu<sub>2</sub>(OH)<sub>2</sub>(NO<sub>3</sub>)<sub>6</sub>(H<sub>2</sub>O)<sub>4</sub>]<sub>2</sub>·11H<sub>2</sub>O (<b>1</b>) and Pu<sub>2</sub>(OH)<sub>2</sub>(NO<sub>3</sub>)<sub>6</sub>(H<sub>2</sub>O)<sub>4</sub>·2H<sub>2</sub>O (<b>2</b>), which differ primarily in the number of incorporated
water molecules. High-energy X-ray scattering (HEXS) data obtained
from the mother liquor showed evidence of a correlation at 3.7(1)
Å but only after concentration of the stock solution. This distance
is consistent with the dihydroxo-bridged distance of 3.799(1) Å
seen in the solid-state structure as well as with the known Pu–Pu
distance in PuO<sub>2</sub>. The structural characterization of a
dihydroxo-bridged Pu moiety is discussed in terms of its relevance
to the underlying mechanisms of tetravalent metal-ion condensation
