Americium compounds

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Americium compounds are compounds containing the element americium (Am). These compounds can form in the +2, +3, and +4, although the +3 oxidation state is the most common. The +5, +6 and +7 oxidation states have also been reported.

Contents

Oxides

Three americium oxides are known, with the oxidation states +2 (AmO), +3 (Am2O3), and +4 (AmO2). Americium(II) oxide was prepared in minute amounts and has not been characterized in detail. [1] Americium(III) oxide is a red-brown solid with a melting point of 2205 °C. [2] Americium(IV) oxide is the main form of solid americium which is used in nearly all its applications. Like most other actinide dioxides, it is a black solid with a cubic (fluorite) crystal structure. [3]

The oxalate of americium(III), vacuum dried at room temperature, has the chemical formula Am2(C2O4)3·7H2O. Upon heating in vacuum, it loses water at 240 °C and starts decomposing into AmO2 at 300 °C, the decomposition completes at about 470 °C. [4] The initial oxalate dissolves in nitric acid with the maximum solubility of 0.25 g/L. [5]

Halides

Halides of americium are known for the oxidation states +2, +3, and +4, [6] where the +3 is most stable, especially in solutions. [7]

Oxidation stateFClBrI
+4 Americium(IV) fluoride
AmF4
pale pink
+3 Americium(III) fluoride
AmF3
pink		 Americium(III) chloride
AmCl3
pink		 Americium(III) bromide
AmBr3
light yellow		 Americium(III) iodide
AmI3
light yellow
+2 Americium(II) chloride
AmCl2
black		 Americium(II) bromide
AmBr2
black		 Americium(II) iodide
AmI2
black

Reduction of Am(III) compounds with sodium amalgam yields Am(II) salts – the black halides AmCl2, AmBr2, and AmI2. They are very sensitive to oxygen and oxidize in water, releasing hydrogen and converting back to the Am(III) state. Specific lattice constants are:

Am + HgX2 (mercury halide) → AmX2 + Hg (at 400–500 °C)

Americium(III) fluoride (AmF3) is poorly soluble and precipitates upon reaction of Am+3 and fluoride ions in weak acidic solutions:

Am+3 + 3F− → AmF3↓

The tetravalent americium(IV) fluoride (AmF4) is obtained by reacting solid americium(III) fluoride with molecular fluorine: [10] [11]

2AmF3 + F2 → 2AmF4

Another known form of solid tetravalent americium fluoride is KAmF5. [10] [12] Tetravalent americium has also been observed in the aqueous phase. For this purpose, black Am(OH)4 was dissolved in 15-M NH4F with the americium concentration of 0.01 M. The resulting reddish solution had a characteristic optical absorption spectrum which is similar to that of AmF4 but differed from other oxidation states of americium. Heating the Am(IV) solution to 90 °C did not result in its disproportionation or reduction, however a slow reduction was observed to Am(III) and assigned to self-irradiation of americium by alpha particles. [13]

Most americium(III) halides form hexagonal crystals with slight variation of the color and exact structure between the halogens. So, chloride (AmCl3) is reddish and has a structure isotypic to uranium(III) chloride (space group P63/m) and the melting point of 715 °C. [6] The fluoride is isotypic to LaF3 (space group P63/mmc) and the iodide to BiI3 (space group R3). The bromide is an exception with the orthorhombic PuBr3-type structure and space group Cmcm. [7] Crystals of americium chloride hexahydrate (AmCl3·6H2O) can be prepared by dissolving americium dioxide in hydrochloric acid and evaporating the liquid. Those crystals are hygroscopic and have yellow-reddish color and a monoclinic crystal structure. [14]

Oxyhalides of americium in the form AmVIO2X2, AmVO2X, AmIVOX2, and AmIIIOX can be obtained by reacting the corresponding americium halide with oxygen or Sb2O3, and AmOCl can also be produced by vapor phase hydrolysis: [9]

AmCl3 + H2O → AmOCl + 2HCl

Other inorganic compounds

Hydroxide

The only known hydroxide of americium is Am(OH)3, which is the first compound of americium, discovered in 1944 as part of the Manhattan project. Americium hydroxide is a pink solid [15] which is sparingly soluble in water. [16]

Due to self-irradiation, the crystal structure of 241Am(OH)3 decomposes within 4 to 6 months (241Am has a half-life of 432.2 years); for 244Cm(OH)3 the same process takes less than a day (244Cm has a half-life of 18.11 years). [15]

When ozone is bubbled through a slurry of americium(III) hydroxide in 0.03 M potassium bicarbonate at 92 °C, hexagonal KAmO2CO3 (potassium dioxoamericium(V) carbonate) can be obtained. Potassium carbonate can also be used. The resulting KAmO2CO3 reacts with dilute acids to produce americium dioxide: [17]

O3 + Am(OH)3 + KHCO3 + H2O → KAmO2CO3 + 3H2O + O2

Chalcogenides and pnictides

The known chalcogenides of americium include the sulfide AmS2, [18] selenides AmSe2 and Am3Se4, [18] [19] and tellurides Am2Te3 and AmTe2. [20] The pnictides of americium (243Am) of the AmX type are known for the elements phosphorus, arsenic, [21] antimony, and bismuth. They crystallize in the rock-salt lattice. [19]

Silicides and borides

Americium monosilicide (AmSi) and "disilicide" (nominally AmSix, with 1.87 < x < 2.0) were obtained by reduction of americium(III) fluoride with elementary silicon in vacuum at 1050 °C (AmSi) and 1150−1200 °C (AmSix). AmSi is a black solid isomorphic with LaSi, it has an orthorhombic crystal symmetry. AmSix has a bright silvery lustre and a tetragonal crystal lattice (space group I41/amd), it is isomorphic with PuSi2 and ThSi2. [22] Borides of americium include AmB4 and AmB6. The tetraboride can be obtained by heating an oxide or halide of americium with magnesium diboride in vacuum or inert atmosphere. [23] [24]

Organoamericium compounds

Predicted structure of amerocene, (e -C8H8)2Am Uranocene-3D-balls.png
Predicted structure of amerocene, (η -C8H8)2Am

Analogous to uranocene, americium forms the organometallic compound amerocene with two cyclooctatetraene ligands, with the chemical formula (η8-C8H8)2Am, [25] but it is still hypothetical up to date. An anionic complex KAm(COT)2 can be prepared by reacting K2COT and AmI3 in THF. [26] A cyclopentadienyl complex is also known that is likely to be stoichiometrically AmCp3. [27] [28]

Formation of the complexes of the type Am(n−C3H7−BTP)3, where BTP stands for 2,6-di(1,2,4-triazin-3-yl)pyridine, in solutions containing n−C3H7−BTP− and Am+3 ions has been confirmed by EXAFS. Some of these BTP-type complexes selectively interact with americium and therefore are useful in its selective separation from lanthanides and another actinides. [29]

See also

Related Research Articles

<span class="mw-page-title-main">Americium</span> Chemical element, symbol Am and atomic number 95

Americium is a synthetic radioactive chemical element with the symbol Am and atomic number 95. It is a transuranic member of the actinide series, in the periodic table located under the lanthanide element europium and was thus named after the United States by analogy.

The actinide or actinoid series encompasses the 14 metallic chemical elements with atomic numbers from 89 to 102, actinium through nobelium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.

<span class="mw-page-title-main">Berkelium</span> Chemical element, symbol Bk and atomic number 97

Berkelium is a transuranic radioactive chemical element with the symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

<span class="mw-page-title-main">Curium</span> Chemical element, symbol Cm and atomic number 96

Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.

<span class="mw-page-title-main">Curium(III) oxide</span> Chemical compound

Curium(III) oxide is a compound composed of curium and oxygen with the chemical formula Cm2O3. It is a crystalline solid with a unit cell that contains two curium atoms and three oxygen atoms. The simplest synthesis equation involves the reaction of curium(III) metal with O2−: 2 Cm3+ + 3 O2− ---> Cm2O3. Curium trioxide can exist as five polymorphic forms. Two of the forms exist at extremely high temperatures, making it difficult for experimental studies to be done on the formation of their structures. The three other possible forms which curium sesquioxide can take are the body-centered cubic form, the monoclinic form, and the hexagonal form. Curium(III) oxide is either white or light tan in color and, while insoluble in water, is soluble in inorganic and mineral acids. Its synthesis was first recognized in 1955.

<span class="mw-page-title-main">Organoactinide chemistry</span> Study of chemical compounds containing actinide-carbon bonds

Organoactinide chemistry is the science exploring the properties, structure, and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.

<span class="mw-page-title-main">Americium(III) chloride</span> Chemical compound

Americium(III) chloride or americium trichloride is the chemical compound composed of americium and chlorine with the formula AmCl3. This salt forms pink hexagonal crystals. In the solid state each americium atom has nine chlorine atoms as near neighbours, at approximately the same distance, in a tricapped trigonal prismatic configuration.

<span class="mw-page-title-main">BTBP</span> A class of tetradentate ligand compounds

The bis-triazinyl bipyridines (BTBPs) are a class of chemical compounds which are tetradentate ligands similar in shape to quaterpyridine. The BTBPs are made by the reaction of hydrazine and a 1,2-diketone with 6,6'-dicyano-2,2'-bipyridine. The dicyanobipy can be made by reacting 2,2'-bipy with hydrogen peroxide in acetic acid, to form 2,2'-bipyridine-N,N-dioxide. The 2,2'-bipyridine-N,N-dioxide is then converted into the dicyano compound by treatment with potassium cyanide and benzoyl chloride in a mixture of water and THF.

<span class="mw-page-title-main">Californium compounds</span>

Few compounds of californium have been made and studied. The only californium ion that is stable in aqueous solutions is the californium(III) cation. The other two oxidation states are IV (strong oxidizing agents) and II (strong reducing agents). The element forms a water-soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide. If problems of availability of the element could be overcome, then CfBr2 and CfI2 would likely be stable.

<span class="mw-page-title-main">Berkelium compounds</span> Any chemical compound having at least one berkelium atom

Berkelium forms a number of chemical compounds, where it normally exists in an oxidation state of +3 or +4, and behaves similarly to its lanthanide analogue, terbium. Like all actinides, berkelium easily dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the trivalent oxidation state. This trivalent state is the most stable, especially in aqueous solutions, but tetravalent berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum chloride-strontium chloride melts. Aqueous solutions of Bk3+ ions are green in most acids. The color of the Bk4+ ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid. Berkelium does not react rapidly with oxygen at room temperature, possibly due to the formation of a protective oxide surface layer; however, it reacts with molten metals, hydrogen, halogens, chalcogens and pnictogens to form various binary compounds. Berkelium can also form several organometallic compounds.

<span class="mw-page-title-main">Americium(III) hydroxide</span> Chemical compound

Americium(III) hydroxide is a radioactive inorganic compound with the chemical formula Am(OH)3. It consists of one americium atom and three hydroxy groups. It was first discovered in 1944, closely related to the Manhattan Project. However, these results were confidential and were only released to the public in 1945. It was the first isolated sample of an americium compound, and the first americium compound discovered.

Curium compounds are compounds containing the element curium (Cm). Curium usually forms compounds in the +3 oxidation state, although compounds with curium in the +4, +5 and +6 oxidation states are also known.

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium in the +3 oxidation state, or in some cases in the +2 and +4 oxidation states. Although einsteinium is relatively stable, with half-lives ranging from 20 days upwards, these compounds have not been studied in great detail.

<span class="mw-page-title-main">Berkelium(III) chloride</span> Chemical compound

Berkelium(III) chloride also known as berkelium trichloride, is a chemical compound with the formula BkCl3. It is a water-soluble green salt with a melting point of 603 °C. This compound forms the hexahydrate, BkCl3·6H2O.

<span class="mw-page-title-main">Terbium compounds</span> Chemical compounds with at least one terbium atom

Terbium compounds are compounds formed by the lanthanide metal terbium (Tb). Terbium generally exhibits the +3 oxidation state in these compounds, such as in TbCl3, Tb(NO3)3 and Tb(CH3COO)3. Compounds with terbium in the +4 oxidation state are also known, such as TbO2 and BaTbF6. Terbium can also form compounds in the 0, +1 and +2 oxidation states.

Protactinium compounds are compounds containing the element protactinium. These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states.

<span class="mw-page-title-main">Berkelium(III) oxide</span> Chemical compound

Berkelium(III) oxide is a binary inorganic compound of berkelium and oxygen with the chemical formula Bk
2O
3.

Einsteinium fluoride is a binary inorganic chemical compound of einsteinium and fluorine with the chemical formula EsF3.

<span class="mw-page-title-main">Curium(IV) oxide</span> Chemical compound

Curium(IV) oxide is an inorganic chemical compound of curium and oxygen with the chemical formula CmO2. Since all isotopes of curium are man-made, the compound does not occur in nature.

<span class="mw-page-title-main">Curium(III) iodide</span> Chemical compound

Curium(III) iodide is the chemical compound with the formula CmI3. Since all isotopes of curium are only artificially produced, the compound has no natural occurrence.

References

  1. ↑ Akimoto, Y. (1967). "A note on AmN and AmO". Journal of Inorganic and Nuclear Chemistry. 29 (10): 2650–2652. doi:10.1016/0022-1902(67)80191-X.
  2. ↑ Wiberg, p. 1972
  3. ↑ Greenwood, p. 1267
  4. ↑ Penneman, p. 4
  5. ↑ Penneman, p. 5
  6. 1 2 Wiberg, p. 1969
  7. 1 2 Asprey, L. B.; Keenan, T. K.; Kruse, F. H. (1965). "Crystal Structures of the Trifluorides, Trichlorides, Tribromides, and Triiodides of Americium and Curium". Inorganic Chemistry. 4 (7): 985. doi:10.1021/ic50029a013. S2CID   96551460.
  8. ↑ Baybarz, R. D. (1973). "The preparation and crystal structures of americium dichloride and dibromide". Journal of Inorganic and Nuclear Chemistry. 35 (2): 483. doi:10.1016/0022-1902(73)80560-3.
  9. 1 2 Greenwood, p. 1272
  10. 1 2 Asprey, L. B. (1954). "New Compounds of Quadrivalent Americium, AmF4, KAmF5". Journal of the American Chemical Society. 76 (7): 2019. doi:10.1021/ja01636a094.
  11. ↑ Greenwood, p. 1271
  12. ↑ Penneman, p. 6
  13. ↑ Asprey, L. B.; Penneman, R. A. (1961). "First Observation of Aqueous Tetravalent Americium1". Journal of the American Chemical Society. 83 (9): 2200. doi:10.1021/ja01470a040.
  14. ↑ Burns, John H.; Peterson, Joseph Richard (1971). "Crystal structures of americium trichloride hexahydrate and berkelium trichloride hexahydrate". Inorganic Chemistry. 10: 147. doi:10.1021/ic50095a029.
  15. 1 2 Krivovichev, Sergey; Burns, Peter; Tananaev, Ivan (2006). Structural Chemistry of Inorganic Actinide Compounds. Elsevier. p. 67. ISBN   978-0-08-046791-7.
  16. ↑ Runde, Wolfgang (2011), "Americium and Curium: Radionuclides", Encyclopedia of Inorganic and Bioinorganic Chemistry, American Cancer Society, doi:10.1002/9781119951438.eibc0438, ISBN   978-1-119-95143-8 , retrieved 2020-03-21
  17. ↑ Penneman, R. A.; Keenan, T. K. (1960-01-01). The Radiochemistry of Americium and Curium (Technical report). doi:10.2172/4187189. OSTI   4187189.
  18. 1 2 Damien, D.; Jove, J. (1971). "Americium disulfide and diselenide". Inorganic and Nuclear Chemistry Letters. 7 (7): 685. doi:10.1016/0020-1650(71)80055-7.
  19. 1 2 Roddy, J. (1974). "Americium metallides: AmAs, AmSb, AmBi, Am3Se4, and AmSe2". Journal of Inorganic and Nuclear Chemistry. 36 (11): 2531. doi:10.1016/0022-1902(74)80466-5.
  20. ↑ Damien, D. (1972). "Americium tritelluride and ditelluride". Inorganic and Nuclear Chemistry Letters. 8 (5): 501. doi:10.1016/0020-1650(72)80262-9.
  21. ↑ Charvillat, J.; Damien, D. (1973). "Americium monoarsenide". Inorganic and Nuclear Chemistry Letters. 9 (5): 559. doi:10.1016/0020-1650(73)80191-6.
  22. ↑ Weigel, F.; Wittmann, F.; Marquart, R. (1977). "Americium monosilicide and "disilicide"". Journal of the Less Common Metals. 56: 47. doi:10.1016/0022-5088(77)90217-X.
  23. ↑ Lupinetti, A. J. et al. U.S. Patent 6,830,738 "Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions", Filed 4 Apr 2002, Issued 14 December 2004
  24. ↑ Eick, Harry A.; Mulford, R. N. R. (1969). "Americium and neptunium borides". Journal of Inorganic and Nuclear Chemistry. 31 (2): 371. doi:10.1016/0022-1902(69)80480-X.
  25. ↑ Elschenbroich, Christoph (2008). Organometallchemie. Vieweg+teubner Verlag. p. 589. ISBN   978-3-8351-0167-8.
  26. ↑ Mueller, Werner; Lindner, Roland. Potassium bis(cyclooctatetraenyl)americium(III). Transplutonium 1975, Proc. Int. Transplutionium Elem. Symp., 4th [Conference]. 1976. pp 131-137.
  27. ↑ Albrecht-Schmitt, Thomas E. (2008). Organometallic and Coordination Chemistry of the Actinides. Springer. p. 8. ISBN   978-3-540-77836-3.
  28. ↑ Dutkiewicz, Michał S.; Apostolidis, Christos; Walter, Olaf; Arnold, Polly L. (30 January 2017). "Reduction chemistry of neptunium cyclopentadienide complexes: from structure to understanding". Chemical Science. 2017 (8): 2553–61. doi:10.1039/C7SC00034K. PMC   5431675 . PMID   28553487.
  29. ↑ Girnt, Denise; Roesky, Peter W.; Geist, Andreas; Ruff, Christian M.; Panak, Petra J.; Denecke, Melissa A. (2010). "6-(3,5-Dimethyl-1H-pyrazol-1-yl)-2,2'-bipyridine as Ligand for Actinide(III)/Lanthanide(III) Separation" (PDF). Inorganic Chemistry. 49 (20): 9627–35. doi:10.1021/ic101309j. PMID   20849125.
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