Synthesis, Structure, and Magnetism of Np<sub>2</sub>O<sub>5</sub>

Forbes, Tori Z.; Burns, Peter C.; Skanthakumar, S.; Soderholm, L.

doi:10.1021/ja069250r

Cited by 69 publications

(78 citation statements)

References 12 publications

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“…Moreover, as clearly shown in Figure 1 b, the smaller values of the U = O distances (1.804(12) and 1.862 (14) ) found for U1 with respect to the distances of the other uranyl groups (1.833(12)-2.022(11) , 1.797(14)-1.941 (12) , and 1.863(13)-1.964 (12) for U4, U2, and U3 respectively) suggest that the valence is localized, with U1 identified as a U VI ion. Very similar values of the U VI =O distances were found in extended frameworks that contain UO 2 2+ ···UO 2 2+ cation-cation interactions.…”

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confidence: 67%

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

et al. 2009

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Cation-cation interactions are a key feature of actinide chemistry. These interactions can be used in two areas that currently attract great interest, namely the expansion of felement supramolecular chemistry and the enhancement of magnetic interactions in actinide compounds. [1][2][3][4][5][6][7][8][9][10][11][12] Moreover, oligomeric cation-cation species that present mutually coordinated actinyl ions are likely to play a crucial role in nuclear waste reprocessing and in the migration of radioactive actinides in the environment. [1] Cation-cation interactions are known to be important in neptunyl(V) structural chemistry, [13] but are more rarely found in uranyl(VI) compounds because of the lower basicity of the UO 2 2+ oxygen atoms. Dimeric compounds formed through the mutual binding of pentavalent uranyl(V) ions have been proposed as intermediates in the disproportionation of pentavalent uranyl ions to UO 2 2+ and U IV species. [14] As a result, bulky ligands have been used in the past few years to disfavor cation-cation interactions and allow the synthesis of rare UO 2 + complexes, [15][16][17][18][19][20][21] which have been the subject of two recent reviews. [21] In some of the reported UO 2 + systems, the ligand bulk does not prevent cation-cation interactions and results in decomposition. However, only two examples of UO 2 + ···UO 2 + intermediate complexes have been reported to date: the tetrameric [UO 2 (dbm) 2 ] 4 [K 4 (CH 3 CN) 4 ] (1) and the dimeric [{UO 2 (dbm) 2 K(18C6)} 2 ] (dbm À = dibenzoylmethanate, 18C6 = [18]crown-6) complexes. [8] The presence of antiferromagnetic coupling between the oxo-bridged uranium centers was unambiguously demonstrated for the dimetallic complex but is less evident for the tetrametallic complex. [8] The decomposition of these polymetallic complexes of pentavalent uranyl ions to UO 2 2+ and U IV species starts rapidly after dissolution in organic solvents and is accelerated by traces of water. From these reactivity studies, it occurred to us that the stability of these polymeric systems could possibly be modulated by fine-tuning the electronic and steric proper-ties of the ligand and coordinating cation. Herein, we report the first example of a UO 2 + ···UO 2 + complex that is highly stable in organic solvents and, significantly, is stable toward hydrolysis. We also describe the selective synthesis and the structure of the first mixed-valent UO 2 + ···UO 2 2+ molecular complex, which provides a rare example of functionalization of the U VI =O group. [20,22] By breaking away from the current trend of using steric bulk to prevent dimer formation and the associated disproportionation of UO 2 + complexes, we show that the non-bulky Schiff base ligand salen 2À (N,N'-bis(salicylidene)ethylenediamine) can stabilize pentavalent uranyl ions through the formation of a highly stable cation-cation complex. Moreover, we demonstrate that the resulting tetrameric uranyl(V) complex exhibits unambiguous antiferromagnetic coupling between the uranium centers.The reaction of the recentl...

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confidence: 67%

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

et al. 2009

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“…The compounds marked in red have not been identified in the present studies but should exist. Np 2 O 5 [28] exists and is mentioned here as an indication of the possible pentavalent state of neptunium. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)…”

Section: The Na-np-o Phase Diagrammentioning

confidence: 93%

Synthesis and crystal structure characterisation of sodium neptunate compounds

Smith

Raison²,

Konings³

2011

Journal of Nuclear Materials

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“…[69] With respect to Np, the only known stable binary oxide, apart from NpO 2 , is Np 2 O 5 , with a structure that can no longer be described as underlying fluorite. [70] In particular, the fluorite derived Np 4 O 9 does not seem to exist. With respect to PuO 2+x , the present calculations confirm the stability of PuO 2 , in line with the majority of experimental investigations on this material.…”

Section: Oxidation and Reduction Energiesmentioning

confidence: 99%

Electronic structure and ionicity of actinide oxides from first principles

et al. 2010

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The ground state electronic structures of the actinide oxides AO, A2O3 and AO2 (A=U, Np, Pu, Am, Cm, Bk, Cf) are determined from first-principles calculations, using the self-interaction corrected local spin-density (SIC-LSD) approximation. Emphasis is put on the degree of f-electron localization, which for AO2 and A2O3 is found to follow the stoichiometry, namely corresponding to A 4+ ions in the dioxide and A 3+ ions in the sesquioxides. In contrast, the A 2+ ionic configuration is not favorable in the monoxides, which therefore become metallic. The energetics of the oxidation and reduction of the actinide dioxides is discussed, and it is found that the dioxide is the most stable oxide for the actinides from Np onwards. Our study reveals a strong link between preferred oxidation number and degree of localization which is confirmed by comparing to the ground state configurations of the corresponding lanthanide oxides. The ionic nature of the actinide oxides emerges from the fact that only those compounds will form where the calculated ground state valency agrees with the nominal valency expected from a simple charge counting.

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Synthesis, Structure, and Magnetism of Np₂O₅

Cited by 69 publications

References 12 publications

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Synthesis and crystal structure characterisation of sodium neptunate compounds

Electronic structure and ionicity of actinide oxides from first principles

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Synthesis, Structure, and Magnetism of Np2O5

Cited by 69 publications

References 12 publications

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Stable Pentavalent Uranyl Species and Selective Assembly of a Polymetallic Mixed‐Valent Uranyl Complex by Cation–Cation Interactions

Synthesis and crystal structure characterisation of sodium neptunate compounds

Electronic structure and ionicity of actinide oxides from first principles

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Synthesis, Structure, and Magnetism of Np₂O₅