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Heptavalent Neptunium in a Gas-Phase Complex: (NpVIIO3+)(NO3–)2

Journal Article · · Inorganic Chemistry
 [1];  [2];  [3];  [1]
  1. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Chemical Sciences Division
  2. Laboratory of Subatomic Physics and Associated Technologies (SUBATECH), UMR CNRS 6457, IN2P3/EMN Nantes, Univ. of Nantes (France)
  3. Lab. of Chemical Interdisciplinarity, Synthesis, Analysis and Modeling (CEISAM), UMR CNRS 6230, Univ. of Nantes (France)
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A central goal of chemistry is to achieve ultimate oxidation states, including in gas-phase complexes with no condensed phase perturbations. In the case of the actinide elements, the highest established oxidation states are labile Pu(VII) and somewhat more stable Np(VII). We have synthesized and characterized gas-phase AnO3(NO3)2- complexes for An = U, Np, and Pu by endothermic NO2 elimination from AnO2(NO3)3-. It was previously demonstrated that the PuO3+ core of PuO3(NO3)2- has a Pu—O• radical bond such that the oxidation state is Pu(VI); it follows that in UO3(NO3)2- it is the stable U(VI) oxidation state. On the basis of the relatively more facile synthesis of NpO3(NO3)2-, a Np(VII) oxidation state is inferred. This interpretation is substantiated by reactivity of the three complexes: NO2 spontaneously adds to UO3(NO3)2- and PuO3(NO3)2- but not to NpO3(NO3)2-. This unreactive character is attributed to a Np(VII)O3+ core with three stable Np=O bonds, this in contrast to reactive U—O• and Pu—O• radical bonds. The computed structures and reaction energies for the three AnO3(NO3)2- support the conclusion that the oxidation states are U(VI), Np(VII), and Pu(VI). These results establish the extreme Np(VII) oxidation state in a gas-phase complex, and demonstrate the inherently greater stability of Np(VII) versus Pu(VII).
Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
Intensive Calculation Center of Pays de la Loire (CCIPL); National Large Intensive Computing Equipment (GENCI); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1436600
Journal Information:
Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 19 Vol. 55; ISSN 0020-1669
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY