Plutonium compounds
{{Short description|Chemical compounds containing the element plutonium}}
[[File:Plutonium in solution.jpg|thumb|Various oxidation states of plutonium in
solution|alt=Five fluids in glass test tubes: violet, Pu(III); dark brown, Pu(IV)HClO4; light purple, Pu(V); light brown, Pu(VI); dark green, Pu(VII)]]
Plutonium compounds are compounds containing the element plutonium (Pu). At room temperature, pure plutonium is silvery in color but gains a tarnish when oxidized.{{cite book |last = Heiserman |first = David L. |title = Exploring Chemical Elements and their Compounds |chapter-url = https://archive.org/details/exploringchemica01heis |chapter-url-access = registration |location = New York (NY) |year = 1992 |publisher = TAB Books |isbn = 0-8306-3018-X |chapter = Element 94: Plutonium |pages = [https://archive.org/details/exploringchemica01heis/page/339 339] }} The element displays four common ionic oxidation states in aqueous solution and one rare one:{{cite book |title = Handbook of Chemistry and Physics |editor-first = David R. |editor-last=Lide |edition = 87th |date = 2006 |publisher = CRC Press, Taylor & Francis Group |location = Boca Raton |isbn = 0-8493-0487-3 |pages=4–27}}
- Pu(III), as Pu3+ (blue lavender)
- Pu(IV), as Pu4+ (yellow brown)
- Pu(V), as {{chem|PuO|2|+}} (light pink){{efn|group = note|The {{chem|PuO|2|+}} ion is unstable in solution and will disproportionate into Pu4+ and {{chem|PuO|2|2+}}; the Pu4+ will then oxidize the remaining {{chem|PuO|2|+}} to {{chem|PuO|2|2+}}, being reduced in turn to Pu3+. Thus, aqueous solutions of {{chem|PuO|2|+}} tend over time towards a mixture of Pu3+ and {{chem|PuO|2|2+}}. Uranium#Aqueous chemistry is unstable for the same reason.{{cite web
|title = Nuclear Criticality Safety Engineering Training Module 10 – Criticality Safety in Material Processing Operations, Part 1
|url = http://ncsp.llnl.gov/ncset/Module10.pdf
|access-date = February 15, 2006
|date = 2002
|last = Crooks
|first = William J.
|url-status = dead
|archive-url = https://web.archive.org/web/20060320153404/http://ncsp.llnl.gov/ncset/Module10.pdf
|archive-date = March 20, 2006
}}}}
- Pu(VI), as {{chem|PuO|2|2+}} (pink orange)
- Pu(VII), as {{chem|PuO|5|3-}} (green)-the heptavalent ion is rare.
The color shown by plutonium solutions depends on both the oxidation state and the nature of the acid anion.{{cite book
|last = Matlack
|first = George
|title = A Plutonium Primer: An Introduction to Plutonium Chemistry and its Radioactivity
|publisher = Los Alamos National Laboratory
|date = 2002
|id = LA-UR-02-6594
}} It is the acid anion that influences the degree of complexing—how atoms connect to a central atom—of the plutonium species. Additionally, the formal +2 oxidation state of plutonium is known in the complex [K(2.2.2-cryptand)] [PuIICp″3], Cp″ = C5H3(SiMe3)2.{{cite journal|doi=10.1021/jacs.7b00706|pmid=28235179|title=Identification of the Formal +2 Oxidation State of Plutonium: Synthesis and Characterization of
A +8 oxidation state is possible as well in the volatile tetroxide {{chem|Pu|O|4}}.{{cite journal |last1=Zaitsevskii |first1=Andréi |last2=Mosyagin |first2=Nikolai S. |last3=Titov |first3=Anatoly V. |last4=Kiselev |first4=Yuri M. |title=Relativistic density functional theory modeling of plutonium and americium higher oxide molecules |journal=The Journal of Chemical Physics |date=21 July 2013 |volume=139 |issue=3 |pages=034307 |doi=10.1063/1.4813284|pmid=23883027 |bibcode=2013JChPh.139c4307Z }} Though it readily decomposes via a reduction mechanism similar to {{chem|Fe|O|4}}, {{chem|Pu|O|4}} can be stabilized in alkaline solutions and chloroform.{{cite journal |last1=Kiselev |first1=Yu. M. |last2=Nikonov |first2=M. V. |last3=Dolzhenko |first3=V. D. |last4=Ermilov |first4=A. Yu. |last5=Tananaev |first5=I. G. |last6=Myasoedov |first6=B. F. |title=On existence and properties of plutonium(VIII) derivatives |journal=Radiochimica Acta |date=17 January 2014 |volume=102 |issue=3 |pages=227–237 |doi=10.1515/ract-2014-2146|s2cid=100915090 }}
Metallic plutonium is produced by reacting plutonium tetrafluoride with barium, calcium or lithium at 1200 °C.{{cite book |title = Concise Encyclopedia Chemistry |url = https://archive.org/details/conciseencyclope00eagl |url-access = registration |last = Eagleson |first = Mary |location = Berlin |publisher = Walter de Gruyter |isbn = 978-3-11-011451-5 |date = 1994 |page = 840}} Metallic plutonium is attacked by acids, oxygen, and steam but not by alkalis and dissolves easily in concentrated hydrochloric, hydroiodic and perchloric acids.{{cite book |title = The Encyclopedia of the Chemical Elements |chapter-url = https://archive.org/details/encyclopediaofch00hamp |chapter-url-access = registration |publisher = Reinhold Book Corporation |location = New York (NY) |year = 1968 |editor = Clifford A. Hampel |last = Miner |first = William N. |author2 = Schonfeld, Fred W. |chapter = Plutonium |pages = [https://archive.org/details/encyclopediaofch00hamp/page/545 540–546] |lccn = 68029938 }} Molten metal must be kept in a vacuum or an inert atmosphere to avoid reaction with air. At 135 °C the metal will ignite in air and will explode if placed in carbon tetrachloride.
File:Plutonium pyrophoricity.jpg can cause it to look like a glowing ember under certain conditions.|alt=Black block of Pu with red spots on top and yellow powder around it]]
Plutonium is a reactive metal. In moist air or moist argon, the metal oxidizes rapidly, producing a mixture of oxides and hydrides.{{cite web
|url = http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419&displaySubstanceName=Plutonium,%20Radioactive&UNNAID=&STCCID=&selectedDataMenuItemID=44
|publisher = U.S. National Library of Medicine, National Institutes of Health
|location = Bethesda (MD)
|title = Plutonium, Radioactive
|work = Wireless Information System for Emergency Responders (WISER)
|access-date = November 23, 2008
|archive-url = https://web.archive.org/web/20110813103852/http://webwiser.nlm.nih.gov/getSubstanceData.do;jsessionid=89B673C34252C77B4C276F2B2D0E4260?substanceID=419&displaySubstanceName=Plutonium,%20Radioactive&UNNAID=&STCCID=&selectedDataMenuItemID=44
|archive-date = August 13, 2011
|url-status = dead
}} (public domain text) If the metal is exposed long enough to a limited amount of water vapor, a powdery surface coating of PuO2 is formed. Also formed is plutonium hydride but an excess of water vapor forms only PuO2.
Plutonium shows enormous, and reversible, reaction rates with pure hydrogen, forming plutonium hydride.{{cite journal
|first = Siegfried S.
|last = Hecker
|title = Plutonium and its alloys: from atoms to microstructure
|journal = Los Alamos Science
|volume = 26
|date = 2000
|pages = 290–335
|url = https://fas.org/sgp/othergov/doe/lanl/pubs/00818035.pdf
|access-date = February 15, 2009
|archive-date = February 24, 2009
|archive-url = https://web.archive.org/web/20090224204042/http://www.fas.org/sgp/othergov/doe/lanl/pubs/00818035.pdf
|url-status = live
}} It also reacts readily with oxygen, forming PuO and PuO2 as well as intermediate oxides; plutonium oxide fills 40% more volume than plutonium metal. The metal reacts with the halogens, giving rise to compounds with the general formula PuX3 where X can be F, Cl, Br or I and PuF4 is also seen. The following oxyhalides are observed: PuOCl, PuOBr and PuOI. It will react with carbon to form PuC, nitrogen to form PuN and silicon to form PuSi2.{{cite book |title = Nature's Building Blocks: An A–Z Guide to the Elements |last = Emsley |first = John |publisher = Oxford University Press |year = 2001 |location = Oxford (UK) |isbn = 0-19-850340-7 |chapter = Plutonium |pages = 324–329}}
The organometallic chemistry of plutonium complexes is typical for organoactinide species; a characteristic example of an organoplutonium compound is plutonocene.{{cite book |last = Greenwood |first = N. N. |author2=Earnshaw, A. |title = Chemistry of the Elements |edition = 2nd |publisher = Butterworth-Heinemann |location = Oxford (UK) |year = 1997 |isbn = 0-7506-3365-4 |page = 1259}}{{Cite journal|last1=Apostolidis|first1=Christos|last2=Walter|first2=Olaf|last3=Vogt|first3=Jochen|last4=Liebing|first4=Phil|last5=Maron|first5=Laurent|last6=Edelmann|first6=Frank T.|date=2017|title=A Structurally Characterized Organometallic Plutonium(IV) Complex|url= |journal=Angewandte Chemie International Edition|language=en|volume=56|issue=18|pages=5066–5070|doi=10.1002/anie.201701858|issn=1521-3773|pmc=5485009|pmid=28371148}} Computational chemistry methods indicate an enhanced covalent character in the plutonium-ligand bonding.
Powders of plutonium, its hydrides and certain oxides like Pu2O3
are pyrophoric, meaning they can ignite spontaneously at ambient temperature and are therefore handled in an inert, dry atmosphere of nitrogen or argon. Bulk plutonium ignites only when heated above 400 °C. Pu2O3 spontaneously heats up and transforms into PuO2, which is stable in dry air, but reacts with water vapor when heated.{{cite web|url=http://www.hss.energy.gov/NuclearSafety/techstds/standard/hdbk1081/hbk1081d.html#ZZ281 |archive-url=https://web.archive.org/web/20070428220410/http://www.hss.energy.gov/NuclearSafety/techstds/standard/hdbk1081/hbk1081d.html |archive-date=April 28, 2007 |title=Primer on Spontaneous Heating and Pyrophoricity – Pyrophoric Metals – Plutonium |publisher=U.S. Department of Energy, Office of Nuclear Safety, Quality Assurance and Environment |date=1994 |location=Washington (DC) |url-status=dead }}
Crucibles used to contain plutonium need to be able to withstand its strongly reducing properties. Refractory metals such as tantalum and tungsten along with the more stable oxides, borides, carbides, nitrides and silicides can tolerate this. Melting in an electric arc furnace can be used to produce small ingots of the metal without the need for a crucible.
Cerium is used as a chemical simulant of plutonium for development of containment, extraction, and other technologies.{{cite journal|title=Low Temperature Reaction of ReillexTM HPQ and Nitric Acid|author=Crooks, W. J.|display-authors=etal|url=http://sti.srs.gov/fulltext/ms2000068/ms2000068.html|doi=10.1081/SEI-120014371|journal=Solvent Extraction and Ion Exchange|volume=20|date=2002|pages=543–559|issue=4–5|s2cid=95081082 |access-date=January 24, 2010|archive-date=June 14, 2011|archive-url=https://web.archive.org/web/20110614053034/http://sti.srs.gov/fulltext/ms2000068/ms2000068.html|url-status=live|url-access=subscription}}
See also
Notes
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