Rubidium superoxide

Rubidium superoxide

Names
Other names Rubidium hyperoxide
Identifiers
CAS Number	12137-25-6
3D model (JSmol)	Interactive image
CompTox Dashboard (EPA)	DTXSID201315494
InChI InChI=1S/O2.Rb/c1-2;/q-1;+1 Key: AFEOXRVICKHWAE-UHFFFAOYSA-N
SMILES O=[O-].[Rb+]
Properties
Chemical formula	RbO2
Molar mass	117.466 g·mol^−1
Appearance	Bright yellow[1]
Structure
Crystal structure	Distorted CaC2 structure[2]
Related compounds
Other cations	Lithium superoxide Sodium superoxide Potassium superoxide Caesium superoxide
Related rubidium oxides	Rubidium suboxide Rubidium oxide Rubidium sesquioxide Rubidium peroxide Rubidium ozonide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Rubidium superoxide or rubidium hyperoxide is a chemical compound with the chemical formula RbO₂. In terms of oxidation states, the negatively charged superoxide and positively charged rubidium give it a structural formula of Rb⁺[O₂]⁻.^[2]

Chemistry

It can be created by slowly exposing elemental rubidium to oxygen gas:^[3]

Rb(s) + O₂(g) → RbO₂(s)

Like other alkali metal hyperoxides, crystals can also be grown in liquid ammonia.^[4]

Between 280 and 360 °C, Rubidium superoxide will decompose, leaving not rubidium sesquioxide (Rb₂O₃), but rather rubidium peroxide (Rb₂O₂).^[3]

2 RbO₂(s) → Rb₂O₂(s) + O₂(g)

An even more oxygen rich compound, that of rubidium ozonide (RbO₃) can be created using RbO₂.^[5]

Properties

Roughly speaking, 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.^[2]

RbO₂ is stable in dry air, but is extremely hygroscopic.^[3]

The compound has been studied as an example of magnetism arising intrinsically from the p-shell.^[6] RbO₂ has been predicted to be a paramagnetic Mott insulator.^[7] At low temperatures, it transitions to antiferromagnetic order, with a Neel temperature of 15 K.^[2]

See also

• Rubidium sesquioxide
• Rubidium oxide

References

1. Astuti, Fahmi; Miyajima, Mizuki; Fukuda, Takahito; Kodani, Masashi; Nakano, Takehito; Kambe, Takashi; Watanabe, Isao (2019). "Synthesis and Characterization of Magnetic Rubidium Superoxide, RbO₂". Materials Science Forum. 966. Trans Tech Publications, Ltd.: 237–242. doi:10.4028/www.scientific.net/msf.966.237. ISSN 1662-9752.
2. Labhart, M.; Raoux, D.; Känzig, W.; Bösch, M. A. (1979-07-01). "Magnetic order in 2p-electron systems: Electron paramagnetic resonance and antiferromagnetic resonance in the alkali hyperoxides KO₂, RbO₂, and CsO₂". Physical Review B. 20 (1). American Physical Society (APS): 53–70. doi:10.1103/physrevb.20.53. ISSN 0163-1829.
3. Kraus, D. L.; Petrocelli, A. W. (1962). "The Thermal Decomposition of Rubidium Superoxide". The Journal of Physical Chemistry. 66 (7). American Chemical Society (ACS): 1225–1227. doi:10.1021/j100813a003. ISSN 0022-3654.
4. Busch, G.; Strässler, S., eds. (1974). "Magnetische und kalorische Eigenschaften von Alkali-Hyperoxid-Kristallen". Physics of Condensed Matter. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 267–291. doi:10.1007/978-3-662-39595-0. ISBN 978-3-662-38713-9.
5. Vol'nov, I. I.; Dobrolyubova, M. S.; Tsentsiper, A. B. (1966). "Synthesis of rubidium ozonide via rubidium superoxide". Bulletin of the Academy of Sciences, USSR Division of Chemical Science. 15 (9). Springer Science and Business Media LLC: 1611–1611. doi:10.1007/bf00848934. ISSN 0568-5230.
6. Kováčik, Roman; Ederer, Claude (2009-10-26). "Correlation effects in p-electron magnets: Electronic structure of RbO₂ from first principles". Physical Review B. 80 (14). American Physical Society (APS): 140411. arXiv:0905.3721. doi:10.1103/physrevb.80.140411. ISSN 1098-0121.
7. Kováčik, Roman; Werner, Philipp; Dymkowski, Krzysztof; Ederer, Claude (2012-08-17). "Rubidium superoxide: A p-electron Mott insulator". Physical Review B. 86 (7). American Physical Society (APS): 075130. arXiv:1206.1423. doi:10.1103/physrevb.86.075130. ISSN 1098-0121.