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Neptunocene

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Neptunocene
Names
IUPAC name Bis(η-cyclooctatetraenyl)neptunium(IV)
Other names Neptunium cyclooctatetraenide
Np(COT)2
Identifiers
CAS Number
3D model (JSmol)
InChI
  • InChI=1S/2C5H5.Np/c2*1-2-4-5-3-1;/h2*1-5H;/q2*-1;+2Key: FXDJOXAJBKYPFW-UHFFFAOYSA-N
SMILES
  • c1=cc=cc=c1..c1=cc=cc=c1
Properties
Chemical formula C16H16Np
Molar mass 445 g·mol
Appearance dark brown crystals as a solid, yellow in dilute solution
Solubility in water insoluble, does not react with water
Solubility in chlorocarbons sparingly soluble (ca. 0.5 g/L)
Hazards
Occupational safety and health (OHS/OSH):
Main hazards radiation hazard, pyrophoric
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). Infobox references
Chemical compound

Neptunocene, Np(C8H8)2, is an organoneptunium compound composed of a neptunium atom sandwiched between two cyclooctatetraenide (COT) rings. As a solid it has a dark brown/red colour but it appears yellow when dissolved in chlorocarbons, in which it is sparingly soluble. The compound is quite air-sensitive.

It was one of the first organoneptunium compounds to be synthesised, and is a member of the actinocene family of actinide-based metallocenes.

Structure

The sandwich structure of neptunocene has been determined by single crystal XRD. The COT rings are found to be planar with 8 equivalent C–C bonds of 1.385 Å length, and sit parallel in an eclipsed conformation. The Np–COT distance (to the ring centroid) is 1.909 Å and the individual Np–C distances are 2.630 Å.

Neptunocene assumes a monoclinic crystal structure (P21/n space group) which is isomorphous to uranocene and thorocene but not to plutonocene.

Synthesis and properties

Neptunocene was first synthesised in 1970 by reacting neptunium(IV) chloride (NpCl4) with dipotassium cyclooctatetraenide (K2(C8H8)) in diethyl ether or THF:

NpCl4 + 2 K2(C8H8) → Np(C8H8)2 + 4 KCl

The same reaction conditions have been routinely reproduced since then for the synthesis of the compound.

The three actinocenes uranocene, neptunocene, and plutonocene share virtually identical chemistry: they do not react in the presence of water or dilute base, but are very air-sensitive, quickly forming oxides. All three are only slightly soluble (up to about 10 M concentrations) in aromatic or chlorinated solvents such as benzene, toluene, carbon tetrachloride or chloroform.

References

  1. ^ Karraker, David G.; Stone, John Austin.; Jones, Erwin Rudolph.; Edelstein, Norman. (1970). "Bis(cyclooctatetraenyl)neptunium(IV) and bis(cyclooctatetraenyl)plutonium(IV)". Journal of the American Chemical Society. 92 (16): 4841–4845. doi:10.1021/ja00719a014. ISSN 0002-7863. Archived from the original on 2024-05-03. Retrieved 2021-03-22.
  2. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1278–1280. ISBN 9780750633659.
  3. ^ Eisenberg, David C.; Streitwieser, Andrew; Kot, Wing K. (1990). "Electron transfer in organouranium and transuranium systems". Inorganic Chemistry. 29 (1): 10–14. doi:10.1021/ic00326a004. ISSN 0020-1669. Archived from the original on 2024-05-03. Retrieved 2021-03-22.
  4. ^ Ridder, D. J. A. De; Rebizant, J.; Apostolidis, C.; Kanellakopulos, B.; Dornberger, E. (1996). "Bis(cyclooctatetraenyl)neptunium(IV)". Acta Crystallographica Section C. 52 (3): 597–600. doi:10.1107/S0108270195013047. ISSN 1600-5759. Archived from the original on 2021-06-12. Retrieved 2021-03-22.
  5. ^ Yoshida, Zenko; Johnson, Stephen G.; Kimura, Takaumi; Krsul, John R. (2006). "Neptunium". In Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean (eds.). The Chemistry of the Actinide and Transactinide Elements (PDF). Vol. 3 (3rd ed.). Dordrecht, the Netherlands: Springer. pp. 699–812. doi:10.1007/1-4020-3598-5_6. Archived from the original (PDF) on 2018-01-17. Retrieved 2016-08-07.
Neptunium compounds
Np(III)
Np(IV)
Organoneptunium(IV) compounds
Np(V)
Np(VI)
Np(VII)
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