Neptunium (VI) and neptunium (VI/V) mixed valence cluster compounds
- Los Alamos National Laboratory
Neptunium has three readily accessible oxidation states, IV, V and VI, which can coexist under certain conditions, with the aqueous soluble neptunyl(V) moiety, {l_brace}NpO{sub 2}{r_brace}{sup +}, of most environmental relevance. Careful control of Np chemistry is required during actinide separation processes. In addition, the long half life of the major alpha emitting isotope ({sup 237}Np, t{sub 1/2} = 2.144 x 10{sup 6} years) renders Np a major contributor to the radiotoxicity of nuclear waste as a function of time. Significant quantities of neptunium are generated in nuclear reactors and the current surge in interest in nuclear power will lead to an increase in our need to further understand the chemistry of this element. It is clearly of importance that Np chemistry is well understood and there have been several recent investigations into the structural, spectroscopic and magnetic properties of Np compounds. However, the vast majority of this chemistry has been performed in aqueous solution, prohibiting the use of air and moisture sensitive ligands. This is in stark contrast to uranium and thorium where inert atmosphere chemistry with moisture sensitive donor ligands has flourished, yielding greater insight into the structural and electronic properties of these early actinides. For the uranyl(VI) moiety, {l_brace}UO{sub 2}{r_brace}{sup 2+}, UO{sub 2}Cl{sub 2}(thf){sub 3} (and the desolvated dimer [UO{sub 2}Cl{sub 2}(thf)]{sub 2}) have proven to be excellent moisture-free reagents for inert atmosphere uranyl chemistry. These starting reagents have been used extensively within our group to study soft donor ligand coordination in the uranyl equatorial plane and oxo-activation to Lewis acid coordination. However, until now the absence of such a starting reagent for Np has limited our ability to extend this chemistry any further across the actinide series, which is required if we are to gain a more complete understanding of 5f element chemistry. The synthesis of [Np{sup VI}O{sub 2}Cl{sub 2}(thf)]{sub n} offers the potential for more detailed exploration of neptunyl(VI) chemistry while the synthesis of the mixed valence cluster complex [{l_brace}Np{sup VI}O{sub 2}Cl{sub 2}{r_brace}{l_brace}Np{sup V}O{sub 2}Cl(thf){sub 3}{r_brace}{sub 2}] allows neptunyl(V) 'cation-cation' interactions to be proved in a molecular system.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC52-06NA25396
- OSTI ID:
- 956688
- Report Number(s):
- LA-UR-08-08089; LA-UR-08-8089; TRN: US1006250
- Journal Information:
- Chemical Communications, Journal Name: Chemical Communications
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ACTINIDES
AIR
AQUEOUS SOLUTIONS
DIMERS
HALF-LIFE
INERT ATMOSPHERE
INTERACTIONS
ISOTOPES
LEWIS ACIDS
LIGANDS
MAGNETIC PROPERTIES
MOISTURE
NEPTUNIUM
NEPTUNIUM 237
NEPTUNYL COMPLEXES
RADIOACTIVE WASTES
REAGENTS
SEPARATION PROCESSES
THORIUM
URANIUM
VALENCE