USING PHOSPHONATES TO PROBE STRUCTURAL DIFFERENCES BETWEEN TRANSURANIUM ELEMENTS AND THEIR PROPOSED SURROGATES

Abstract

A variety of transuranium phosphonates have now been prepared and structurally characterized allowing for comparisons to be made with other metal ions that have been proposed to be surrogates for transuranics (e.g., Zr⁴⁺, Ce⁴⁺, Th⁴⁺, and U⁴⁺). The phosphonates that will be discussed in this work include Np(CH₃PO₃)(CH₃PO₃H)(NO₃)(H₂O)·H₂O, Pu(CH₃PO₃)₂, M[CH₂(PO₃)₂](H₂O)_n (M=Ce, Th, U, Np, Pu; n = 0 − 2), and UO₂An(H₂O)₂[CH₂(PO₃)(PO₃H)]₂ (An = Th, Np, Pu). Through the examination of these structures, rare coordination geometries for actinides have been uncovered. Simple periodic trends based solely on ionic radii are absent. However, there are examples where surrogate elements adopt the same composition and structure as transuranics, such as Pu(CH₃PO₃)₂ versus Zr(CH₃PO₃)₂.

Keywords:

• actinide phosphonates
• cerium phosphonates
• mixed-actinide phosphonates
• surrogates

Notes

^a .

^b .