Neptunium(III) chloride

Neptunium(III) chloride
Names
IUPAC name
Neptunium(III) chloride
Other names
Neptunium trichloride
Identifiers
3D model (JSmol)
  • InChI=1S/3ClH.Np/h3*1H;/q;;;+3/p-3
    Key: YCRHCDNZKKGRFF-UHFFFAOYSA-K
  • [Cl-].[Np+3].[Cl-].[Cl-]
Properties
NpCl3
Molar mass 343.41 g/mol
Appearance green solid[1]: 731 
Melting point 797 °C (1,467 °F; 1,070 K)[2]
Related compounds
Other anions
 Neptunium(III) fluoride
Neptunium(III) bromide
Neptunium(III) iodide
Other cations
 Uranium(III) chloride
Plutonium(III) chloride
Americium(III) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Neptunium(III) chloride or neptunium trichloride is a chemical compound of neptunium and chlorine with the chemical formula NpCl3. It is hygroscopic, absorbing moisture in air to form a hydrate. Hydrates can also be formed from solutions. The anhydrous form can be prepared in several ways, many involving the reduction of neptunium(IV) chloride (NpCl4), though other reactions can be used as well. It can be used in molten-salt reactors, and it is paramagnetic.

Anhydrous neptunium(III) chloride adopts the same hexagonal structure as uranium(III) chloride. The structure of its hydrates are apparently unknown, but it is predicted that it will form a hydrate of composition NpCl3·7H2O with the same structure as corresponding lanthanide compounds. Neptunium(III) chloride forms adducts with ligands such as pyridine (py; C5H5N), with the formula NpCl3(py)4. This adduct is a useful starting material for preparation of other neptunium compounds.

Synthesis

Hydrate

Neptunium(III) chloride hydrates can be produced from a neptunium chloride solution, prepared from dissolving neptunium compounds in hydrochloric acid (HCl). A reducing agent like hydroxylammonium chloride ([NH3OH]Cl) has to be added to convert neptunium to the +3 oxidation state. The hydrates precipitate upon letting the solution evaporate until dry.[3] Hydrates are also formed by the reaction of anhydrous neptunium(III) chloride with moisture.[4]: 2416 

Anhydrous

Anhydrous neptunium(III) chloride can be made by reacting neptunium(III) chloride hydrate that has been precipitated from solution with thionyl chloride (SOCl2). It is separated from SOCl2 by heating the product in a vacuum.[3] Hydrate reaction with thionyl chloride proceeds like so:[5]

NpCl3·xH2O + x SOCl2 → NpCl3 + x SOCl2 + 2x HCl

Neptunium(III) chloride is also produced from the reduction of neptunium(IV) chloride (NpCl4). Neptunium(IV) chloride can be prepared by the reaction of neptunium(IV) oxide (NpO2) with carbon tetrachloride (CCl4) or a combination of chlorine gas (Cl2) and CCl4. Alternatively, neptunium(IV) oxalate (Np(C2O4)2) can be reacted with CCl4 to make NpCl4. Oxide reaction with CCl4 proceeds like so:[2][6]

NpO2 + 2 CCl4 → NpCl4 + 2 COCl2

Reduction of NpCl4 with hydrogen gas (H2), ammonia (NH3), or zinc yields neptunium(III) chloride. Reacting neptunium(IV) oxide with a mixture of CCl4 and hydrogen gas produces NpCl3 as well.[2][6]

2 NpCl4 + H2 → 2 NpCl3 + 2 HCl
6 NpCl4 + 2 NH3 → 6 NpCl3 + 6 HCl + N2[7]

Carbon tetrachloride is corrosive, so other reagents may be used instead. For example, reaction of neptunium nitride (NpN) with cadmium chloride (CdCl2) by heating a ground mixture of the two compounds produces neptunium(III) chloride:[2]

2 NpN + 3 CdCl2 → 2 NpCl3 + 3 Cd + N2

Properties

Like other actinide(III) chlorides, neptunium(III) chloride is hygroscopic, absorbing moisture from the air to form a hydrate.[4]: 2416  While information as to the composition of neptunium(III) chloride hydrates is unavailable, comparisons with lanthanide trichlorides suggest that neptunium should form a heptahydrate (NpCl3·7H2O) based on neptunium's ionic radius.[8] Below 50 K, neptunium(III) chloride exhibits temperature-independent paramagnetism, and at higher temperatures, it shows Curie–Weiss paramagnetism.[9]

Structure

Anhydrous neptunium(III) chloride possesses the uranium(III) chloride-type crystal structure. This structure is hexagonal. It features neptunium bonding with nine chlorine atoms, where neptunium has a coordination geometry of tricapped trigonal prismatic; six chlorine atoms form a triangular prism around the neptunium atom, and the remaining three cap off the rectangular faces. The bases of the prisms join together to form infinite chains.[10]: 131 [11]: 1096–1097 

The crystal structure of NpCl3. Blue is neptunium, green is chlorine.
The coordination sphere of each neptunium atom in the structure of NpCl3. Blue is neptunium, green is chlorine.
The coordination sphere of each chlorine atom in the structure of NpCl3. Blue is neptunium, green is chlorine.

As for hydrates, neptunium(III) chloride is predicted to form a heptahydrate, NpCl3·7H2O, which would be isostructural with corresponding lanthanide compounds.[8] These compounds consist of dimeric units of formula M2Cl2(H2O)4+14 (M=metal), which feature each metal atom bonded to seven water molecules. Two chloride ions bridge the metal centers. These units are linked together by additional chloride ions, which bond to the water molecules through hydrogen bonds. This structure can be represented as [(H2O)7M(μ2-Cl2)M(H2O)4+7]Cl4.[12]

Complexes

With pyridine

An adduct of neptunium(III) chloride with pyridine (C5H5N), with the composition NpCl3(py)4 (py = pyridine) is known. The synthesis of this compound starts from the dimethoxyethane adduct of neptunium(IV) chloride, NpCl4(DME)2 (DME = dimethoxyethane). Dissolving this compound in tetrahydrofuran (C4H8O; THF) produces a tetrahydrofuran adduct, NpCl4(THF)3. Reducing this compound with caesium graphite forms a yellow powder, presumably NpCl3(THF)x. Dissolving this compound in pyridine and subsequently in ethyl ether, (C2H5)2O, affords the pyridine adduct.[13] This compound has replaced NpI3(THF)4 as a useful starting material for synthesizing other neptunium compounds, as NpI3(THF)4 requires the use of neptunium metal.[14]

Uses

Neptunium(III) chloride can be used in molten-salt reactors, a type of nuclear reactor in which the fuel and/or the coolant is a molten salt. In this case, neptunium(III) chloride is used as the fuel. Neptunium(III) chloride is combined with other salts, like other actinide chlorides or halides of alkali metals.[15][16]

References

  1. ^ Yoshida, Zenko; Johnson, Stephen; Kimura, Takaumi; Krsul, John (2011). "Neptunium". The Chemistry of the Actinide and Transactinide Elements. doi:10.1007/978-94-007-0211-0_6. ISBN 978-1-4020-3555-5.
  2. ^ a b c d Hayashi, Hirokazu; Takano, Masahide; Kurata, Masaki; Minato, Kazuo (2013). "Syntheses of neptunium trichloride and measurements of its melting temperature". Journal of Nuclear Materials. 440 (1–3): 477–479. Bibcode:2013JNuM..440..477H. doi:10.1016/j.jnucmat.2013.01.316.
  3. ^ a b "Dehydration of plutonium or neptunium trichloride hydrate".
  4. ^ a b Gutowski, Keith E.; Bridges, Nicholas J.; Rogers, Robin D. (2010). "Actinide Structural Chemistry". The Chemistry of the Actinide and Transactinide Elements. pp. 2380–2523. doi:10.1007/978-94-007-0211-0_22. ISBN 978-94-007-0210-3.
  5. ^ Pray, Alfred R.; Heitmiller, Richard F.; Strycker, Stanley; Aftandilian, Victor D.; Muniyappan, T.; Choudhury, D.; Tamres, Milton (1990). "Anhydrous Metal Chlorides". Inorganic Syntheses. Vol. 28. pp. 321–323. doi:10.1002/9780470132593.ch80. ISBN 978-0-471-52619-3.
  6. ^ a b Fried, S.; Davidson, N.R. "The Basic Dry Chemistry of Neptunium" (PDF).
  7. ^ Sheft, Irving; Fried, Sherman (1953). "New Neptunium Compounds". Journal of the American Chemical Society. 75 (5): 1236–1237. Bibcode:1953JAChS..75.1236S. doi:10.1021/ja01101a067.
  8. ^ a b Burns, John H.; Peterson, Joseph Richard (1971). "Crystal structures of americium trichloride hexahydrate and berkelium trichloride hexahydrate". Inorganic Chemistry. 10: 147–151. doi:10.1021/ic50095a029.
  9. ^ Jones, E. R.; Hendricks, M. E.; Stone, J. A.; Karraker, D. G. (1974). "Magnetic properties of the trichlorides, tribromides, and triiodides of U(III), Np(III), and Pu(III)". The Journal of Chemical Physics. 60 (5): 2088–2094. Bibcode:1974JChPh..60.2088J. doi:10.1063/1.1681318.
  10. ^ Brown, David (1972). "Compounds with Chlorine". Transurane. pp. 129–147. doi:10.1007/978-3-662-11547-3_7. ISBN 978-3-662-11548-0.
  11. ^ Clark, David L.; Hecker, Siegfried S.; Jarvinen, Gordon D.; Neu, Mary P. (2011). "Plutonium". The Chemistry of the Actinide and Transactinide Elements (PDF). doi:10.1007/978-94-007-0211-0_7. ISBN 978-94-007-0211-0.
  12. ^ Kandabadage, Thimira; Legnon, Beau; Baranets, Sviatoslav (2024). "Comprehensive structural study of lanthanide(III) chloride hydrates: [RECl3·xH2O (RE = La–Nd, Sm–Lu; x = 6, 7)]". Acta Crystallographica Section E. 80 (12): 1342–1349. Bibcode:2024AcCrE..80.1342K. doi:10.1107/S2056989024011319. PMC 11789172. PMID 39906789.
  13. ^ Pattenaude, Scott A.; Anderson, Nickolas H.; Bart, Suzanne C.; Gaunt, Andrew J.; Scott, Brian L. (2018). "Non-aqueous neptunium and plutonium redox behaviour in THF – access to a rare Np(III) synthetic precursor". Chemical Communications. 54 (48): 6113–6116. doi:10.1039/C8CC02611D. OSTI 1436357. PMID 29736543.
  14. ^ Myers, Alexander J.; Tarlton, Michael L.; Kelley, Steven P.; Lukens, Wayne W.; Walensky, Justin R. (2019). "Synthesis and Utility of Neptunium(III) Hydrocarbyl Complex". Angewandte Chemie International Edition. 58 (42): 14891–14895. Bibcode:2019ACIE...5814891M. doi:10.1002/anie.201906324. PMID 31412157.
  15. ^ "What are Molten Salt Reactors?". 11 March 2025.
  16. ^ "Salt compositions for molten salt reactors".
This article is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.