rubidium superoxide
{{Chembox
| ImageFile =
| ImageSize =
| Name =
| OtherNames = Rubidium hyperoxide
|Section1 = {{Chembox Identifiers
| CASNo = 12137-25-6
| CASNo_Ref =
| SMILES = O=[O-].[Rb+]
| StdInChI=1S/O2.Rb/c1-2;/q-1;+1
| StdInChIKey=AFEOXRVICKHWAE-UHFFFAOYSA-N
}}
|Section2 = {{Chembox Properties
| Formula = {{chem2|RbO2}}
| Rb=1|O=2
| Density=
| MeltingPt=
}}
|Section3 = {{Chembox Structure
| Structure_ref =
| CrystalStruct = Distorted Calcium acetylide structure{{cite journal | last=Labhart | first=M. | last2=Raoux | first2=D. | last3=Känzig | first3=W. | last4=Bösch | first4=M. A. | title=Magnetic order in 2p-electron systems: Electron paramagnetic resonance and antiferromagnetic resonance in the alkali hyperoxides KO2, RbO2, and CsO2 | journal=Physical Review B | publisher=American Physical Society (APS) | volume=20 | issue=1 | date=1979-07-01 | issn=0163-1829 | doi=10.1103/physrevb.20.53 | pages=53–70}}
| SpaceGroup =
| LattConst_a =
| LattConst_Comment =
| UnitCellVolume =
| UnitCellFormulas =
| Coordination =
}}
|Section8={{Chembox Related
| OtherAnions =
| OtherCations = {{ubl|Lithium superoxide|Sodium superoxide|Potassium superoxide|Caesium superoxide}}
| OtherFunction = {{ubl|Rubidium suboxide|Rubidium oxide|Rubidium sesquioxide|Rubidium peroxide|Rubidium ozonide}}
| OtherFunction_label = rubidium oxides
}}
}}
Rubidium superoxide or rubidium hyperoxide is a chemical compound with the chemical formula {{chem2|RbO2}}. In terms of oxidation states, the negatively charged superoxide and positively charged rubidium give it a structural formula of {{chem2|Rb+[O2]−}}.
Chemistry
It can be created by slowly exposing elemental rubidium to oxygen gas:{{cite journal | last=Kraus | first=D. L. | last2=Petrocelli | first2=A. W. | title=The Thermal Decomposition of Rubidium Superoxide | journal=The Journal of Physical Chemistry | publisher=American Chemical Society (ACS) | volume=66 | issue=7 | year=1962 | issn=0022-3654 | doi=10.1021/j100813a003 | pages=1225–1227}}
:{{chem2|Rb(s) + O2(g) → RbO2(s)}}
Like other alkali metal hyperoxides, crystals can also be grown in liquid ammonia.{{cite book | editor-last=Busch | editor-first=G. | editor-last2=Strässler | editor-first2=S. | title=Physics of Condensed Matter | publisher=Springer Berlin Heidelberg | publication-place=Berlin, Heidelberg | year=1974 | isbn=978-3-662-38713-9 | doi=10.1007/978-3-662-39595-0 | pages=267–291|chapter=Magnetische und kalorische Eigenschaften von Alkali-Hyperoxid-Kristallen}}
Between 280 and 360 °C, Rubidium superoxide will decompose, leaving not rubidium sesquioxide ({{chem2|Rb2O3}}), but rather rubidium peroxide ({{chem2|Rb2O2}}).
:{{chem2|2 RbO2(s) → Rb2O2(s) + O2(g)}}
An even more oxygen rich compound, that of rubidium ozonide ({{chem2|RbO3}}) can be created using {{chem2|RbO2}}.{{cite journal | last=Vol'nov | first=I. I. | last2=Dobrolyubova | first2=M. S. | last3=Tsentsiper | first3=A. B. | title=Synthesis of rubidium ozonide via rubidium superoxide | journal=Bulletin of the Academy of Sciences, USSR Division of Chemical Science | publisher=Springer Science and Business Media LLC | volume=15 | issue=9 | year=1966 | issn=0568-5230 | doi=10.1007/bf00848934 | pages=1611–1611}}
Properties
Roughly speaking, {{chem2|RbO2}} has a crystal structure similar to tetragonal calcium carbide, but is rather distorted due to the Jahn–Teller effect, which makes the crystal structure less symmetrical.
{{chem2|RbO2}} is stable in dry air, but is extremely hygroscopic.
The compound has been studied as an example of magnetism arising intrinsically from the p-shell.{{cite journal | last=Kováčik | first=Roman | last2=Ederer | first2=Claude | title=Correlation effects in p-electron magnets: Electronic structure of RbO2 from first principles | journal=Physical Review B | publisher=American Physical Society (APS) | volume=80 | issue=14 | date=2009-10-26 | issn=1098-0121 | doi=10.1103/physrevb.80.140411 | page=140411|arxiv=0905.3721}} {{chem2|RbO2}} has been predicted to be a paramagnetic Mott insulator.{{cite journal | last=Kováčik | first=Roman | last2=Werner | first2=Philipp | last3=Dymkowski | first3=Krzysztof | last4=Ederer | first4=Claude | title=Rubidium superoxide: A p-electron Mott insulator | journal=Physical Review B | publisher=American Physical Society (APS) | volume=86 | issue=7 | date=2012-08-17 | issn=1098-0121 | doi=10.1103/physrevb.86.075130 | page=075130|arxiv=1206.1423}} At low temperatures, it transitions to antiferromagnetic order, with a Neel temperature of 15 K.