Uranium(IV) Sulfates: Investigating Structural Periodicity in the Tetravalent Actinides

Chemical trends within the periodic table are frequently
used as
guides for predicting reactivity, structure, and electronic properties
of the elements. While these trends have been rigorously investigated
for the transition metals, the understanding of trends within the
actinide series is elementary in comparison. Herein, we report the
synthesis and characterization of five new U­(IV) sulfate compounds
and discuss their relationship to previously reported An­(IV) sulfate
species, an analysis that allows for the elucidation of solid state
trends across the actinides. One such trend suggests the increase
in Lewis acidity that occurs when traversing the actinides from thorium
to plutonium promotes bidentate binding of the sulfate ligand as long
as complexation can outcompete the resulting increase in steric pressure.
This hypothesis correlates well with the experimental results previously
reported for the solution phase speciation in An­(IV) sulfate systems.