Hydrothermal synthesis and structure of K6[(UO2)4(CrO4)7]·6H2O: A layered uranyl chromate with a new uranyl sheet topology
2003; Elsevier BV; Volume: 177; Issue: 4-5 Linguagem: Inglês
10.1016/j.jssc.2003.11.025
ISSN1095-726X
AutoresRichard E. Sykora, Steven M. McDaniel, Thomas E. Albrecht‐Schmitt,
Tópico(s)Nuclear materials and radiation effects
ResumoThe layered uranyl chromate, K6[(UO2)4(CrO4)7]·6H2O (1), has been synthesized by reacting UO3 with K2Cr2O7 under mild hydrothermal conditions. The structure of 1 is formed from UO22+ cations that are bound by chromate anions to yield a pentagonal bipyramidal geometry around the uranium centers. These polyhedra are bridged by chromate anions to yield one-dimensional ∞1[UO2(CrO4)2]2− chains. The chains are similar to the ∞1[UO2(CrO4)2(H2O)]2− chains found in the previously reported one-dimensional uranyl chromate, K2[UO2(CrO4)2(H2O)]·3H2O, a phase that forms concomitantly with 1. These chains are condensed with the loss of the coordinated water molecules into two-dimensional ∞2[(UO2)4(CrO4)7]6− layers with additional one-dimensional ∞1[(UO2)2(CrO4)3]2− chains. These anionic layers form a new type of anionic sheet topology and are charge balanced by both intra- and interlayer K+ cations. Crystallographic data (193 K): 1, orthorhombic, space group P21212, a=10.9583(5) Å, b=22.582(1) Å, c=7.9552(4) Å, Z=2, MoKα, λ=0.71073, R(F)=1.77% for 268 parameters with 4657 reflections with I>2σ(I).
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