Periodic Trends in Actinide Phosphonates: Divergence and Convergence between Thorium, Uranium, Neptunium, and Plutonium Systems

The hydrothermal reactions of both PuO22+ and PuO2 with phosphonates results in the formation of Pu(IV) phosphonates. Pu(CH3PO3)2, Pu[CH2(PO3)2](H2O), and UO2Pu(H2O)2[CH2(PO3)(PO3H)]2 have been isolated from these reactions and structurally characterized. Pu(CH3PO3)2 contains six-coordinate Pu(IV) and adopts a structure closely related to that of α-Zr(HPO4)2. Pu[CH2(PO3)2](H2O) forms a novel three-dimensional network with seven-coordinate Pu(IV) and chelating/bridging [CH2(PO3)2]4− anions. The heterobimetallic U(VI)/Pu(IV) diphosphonate, UO2Pu(H2O)2[CH2(PO3)(PO3H)]2, also forms a three-dimensional network. To complete the An[CH2(PO3)2](H2O)n (An = Th, U, Np, Pu; n = 1, 2) and UO2An(H2O)2[CH2(PO3)(PO3H)]2 series, Th[CH2(PO3)2](H2O)2 and UO2Th(H2O)2[CH2(PO3)(PO3H)]2 have also been prepared. These compounds are isostructural with their Np(IV) analogues.

二氧钚(VI)离子（PuO₂²⁺）与二氧化钚（PuO₂）分别与膦酸盐（phosphonates）发生水热反应，均可生成四价钚（Pu(IV)）膦酸盐化合物。从该类反应体系中已分离得到Pu(CH₃PO₃)₂、Pu[CH₂(PO₃)₂](H₂O)以及UO₂Pu(H₂O)₂[CH₂(PO₃)(PO₃H)]₂，并完成了结构表征。Pu(CH₃PO₃)₂中的四价钚为六配位，其晶体结构与α-Zr(HPO₄)₂高度相似。Pu[CH₂(PO₃)₂](H₂O)形成了一种新型三维网络结构，其中四价钚为七配位，配体为兼具螯合与桥联作用的[CH₂(PO₃)₂]⁴⁻阴离子。该异双金属六价铀(U(VI))/四价钚二膦酸盐化合物UO₂Pu(H₂O)₂[CH₂(PO₃)(PO₃H)]₂同样构建出三维网络结构。为完善通式为An[CH₂(PO₃)₂](H₂O)ₙ（An=钍(Th)、铀(U)、镎(Np)、钚(Pu)；n=1,2）以及UO₂An(H₂O)₂[CH₂(PO₃)(PO₃H)]₂的化合物系列，还制备得到了Th[CH₂(PO₃)₂](H₂O)₂与UO₂Th(H₂O)₂[CH₂(PO₃)(PO₃H)]₂。上述化合物与其对应的四价镎(Np(IV))同系物为同构异构体。