Syntheses, structures, and spectroscopic properties of plutonium and americium phosphites and the redetermination of the ionic radii of Pu(III) and Am(III)

A series of isotypic rare earth phosphites (RE = Ce(III), Pr(III), Nd(III), Pu(III), or Am(III)) with the general formulas RE ₂(HPO ₃) ₃(H ₂O) along with a Pu(IV) phosphite, Pu[(HPO ₃) ₂(H ₂O) ₂], have been prepared hydrothermally via reactions of RECl ₃ with phosphorous acid. The structure of RE ₂(HPO ₃) ₃(H ₂O) features a face-sharing interaction of eight- and nine-coordinate rare earth polyhedra. By use of the crystallographic data from the isotypic series along with data from previously reported isotypic series, the ionic radii for higher coordinate Pu(III) and Am(III) were calculated. The ^VIIIPu(III) radius was calculated as 1.112 ± 0.004 Å, and the ^IXPu(III) radius was calculated to be 1.165 ± 0.002 Å. The ^VIIIAm(III) radius was calculated as 1.108 ± 0.004 Å, and the ^IXAm(III) radius was calculated as 1.162 ± 0.002 Å.