Sulfate Compounds of Hexavalent Neptunium and Plutonium

Abstract

Neptunium / Plutonium / Sulfate compounds / Crystallographic structure / Infra-red spectra / Optical spectra Summary Several techniques, X-ray diffraction, thermogravimetry, IR and optical spectroscopy were applied to study the formation of solid Np(VI) and Pu(VI) compounds with S0 4 2-oxoanions. In case of solutions containing equimolar amounts of Np0 2 2+ and cesium sulfate only one compound Cs 2 (Np0 2 ) 2 (S0 4 ), was obtained in crystalline form. But in solutions containing Np0 2 2+ (Pu0 2 2+ ) sulfates with a molar ratio [Cs]: [Np](Pu) higher than 2:1, Cs 2 Np0 2 (S0 4 ) 2 as well as Cs 2 Pu0 2 (S0 4 ) 2 were precipitated. The crystal structure of Cs 2 Np0 2 (S0 4 ) 2 is of layered type and is built up by anionic layers [Np0 2 (S0 4 ) 2 ]" 2 "~ linked together by Cs + ions. Each Np atom in the anionic layer is linked via the sulfateions to three other atoms by such a manner that the bonds form an hexagonal net. Attempts to synthesize hydrated sulfate compounds of Np(VI) and Pu(VI) with cesium via the slow solution evaporation procedure were unsuccessful.

A Novel Family of Np(VI) Oxysalts: Crystal Structures, Calorimetry, Thermal Behavior, and Comparison with U(VI) Compounds

“…Each of the linear actinyl ions is coordinated by five O atoms arranged in the equatorial plane of the corresponding pentagonal bipyramid and belong to sulfate or selenate groups with average bond lengths equal to 2.385 Å (at T = 150 K) for both Npt and Ur cations. Thus, it can be assumed that the decrease in the cation size with incorporation of an additional electron into the configuration of Np (in comparison with U) leads to reduction of the multiple actinyl bond lengths and slight elongation (0.01–0.02 Å) of the equatorial bond lengths, which results in the flattening of neptunyl pentagonal bipyramids slightly in comparison to the uranyl analogues, which is in agreement with previous studies. − …”

Crystal Structures and Magnetic Properties of NaK3(NpO2)4(SO4)4(H2O)2and NaNpO2SO4H2O: Cation−Cation Interactions in a Neptunyl Sulfate Framework

“…In solution the uranyl(VI), neptunyl(VI), and neptunyl(V) ions have AnO bond lengths of 1.77(1), 1.73(2), and 1.80(2) Å, respectively. , The dioxo cations are equatorially coordinated by H 2 O groups with bond lengths of 2.41(8), 2.44(3), and 2.36(3) Å for U 6+ , Np 5+ , and Np 6+ , respectively. , In solution Np 6+ tends to have shorter bonds than Np 5+ , and the same trend is also present in the solid state. In Cs 2 Np(VI)O 2 (SO 4 ) 2 , the bond lengths for Np 6+ are 1.75(1) Å for the neptunyl ion and 2.37(19) Å for equatorial coordination . The average bond lengths for the reported Np 5+ sulfates are 1.83(1) Å for the dioxo ion and 2.48(6) Å for the equatorial distances. − KS2-2 and NaS2-2 display average bond lengths of 1.84(1) Å for the neptunyl ion and 2.46(1) Å for the equatorial ligands, which is consistent with the pentavalent state of neptunium.…”

“…In Cs 2 Np(VI)O 2 (SO 4 ) 2 , the bond lengths for Np 6+ are 1.75-(1) Å for the neptunyl ion and 2.37 (19) Å for equatorial coordination. 21 The average bond lengths for the reported Np 5+ sulfates are 1.83(1) Å for the dioxo ion and 2.48(6) Å for the equatorial distances. [22][23][24][25] KS2-2 and NaS2-2 display average bond lengths of 1.84(1) Å for the neptunyl ion and 2.46(1) Å for the equatorial ligands, which is consistent with the pentavalent state of neptunium.…”

Crystallographic Insights into Uranyl Sulfate Minerals Formation: Synthesis and Crystal Structures of Three Novel Cesium Uranyl Sulfates

“…This topology is rather rare but has been observed in the structures of a few actinide-bearing compounds. It has been described at first in the structure of isotypic Cs neptunyl sulfate compound [25], and later in the structures of Ba uranyl selenite [26] and organically templated uranyl sulfate [27].…”