Xenon nitrate

Xenon nitrate is a transient compound made by reacting xenon difluoride with anhydrous nitric acid. Although xenon dinitrate (Xe(NO₃)₂) has not been isolated and characterised a related mononitrate: xenon fluoride nitrate has been made and studied.

Production

Attempted production has used this method:^[1]

XeF₂ + 2HNO₃ → Xe(NO₃)₂ + 2HF^[2][3]

This reaction made a red-brown solid, that turned blue temporarily as it decomposed spontaneously at 23°C.^[2]

However this decomposes rapidly: Xe(NO₃)₂ → Xe + O₂NOONO₂ (an unstable nitrogen peroxide)

However a nixed nitrate definitely exists FXeONO₂.^[1] This has been called fluoroxenonium nitrate^[4] and xenon fluoride nitrate.^[5]

This is formed via the reaction:^[1]

[FXeOXeFXeF][AsF₆] + 2NO₂F → FXeONO₂ +NO₂AsF₆.

Purification of FXeONO₂ can take place by dissolving in SO₂ClF which leaves the nitronium arsenic hexafluoride behind as a solid.^[1]

An alternate low yield method to make FXeONO₂ is to dissolve xenon difluoride in liquid dinitrogen tetroxide.^[1]

Xe₂ + NO⁺ + NO₃⁻ → FXeONO₂ + NOF at 0°C

This method is inefficient as not much nitrate ion exists in the liquid and the xenon nitrate decomposes.^[1]

Another method claimed to make this substance is:^[1]

XeF₂ + HNO₃ → FXeNO₃ + HF

Properties

FXeONO₂ is a white crystalline material.^[1] The space group of the crystals is P2₁/c which is monoclinic. The unit cell contains four molecules with a total volume of 386.6 Å³. The unit cell dimensions are a=4.6663, b=8.799 Å c=9.415 Å, and non-perpendicular angle β=90.325° and with other axes angles α and γ = 90°.^[1] With a molecular weight of 212.3 the crystal has density 3.648. (These measurements at -173°C.)^[1]

The molecule has bond lengths of xenon to fluorine 1.992 Å, xenon to oxygen 2.126 Å, xenon bonded oxygen to nitrogen 1.36 Å, and other nitrate oxygen bonds are 1.199 (cis) and 1.224 Å (trans).^[1] The bond angles are FXeO 177.6°, XeON 114.7°, (Xe)ONO 114.5° (cis), other (Xe)ONO 118.4° (trans) and (non-Xe)ONO is 127.1°.^[1] The bond lengths and angles on the xenon atom are similar to that in FXeOSO₂F and FXeOTeF₅ indicating a polar oxygen bond. The Xe-O-N angle is larger than halogen nitrates, which indicates a lower bond density for Xe-O bond. N-O_cis bond length is longer than the N-O_trans bond length, the opposite to other halogen nitrates.^[1]

FXeONO₂ is not particularly stable and slowly breaks down at -78°C yielding XeF₂.N₂O₄. This happens on a timescale of several days.^[1] At 0°C FXeONO₂ has a half life of seven hours decomposing to XeF₂.^[1]

References

1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Moran, Matthew D. (2007). Synthesis and Structural Characterization of new Xenon(II) Compounds and the Use of a Xenon(II) Cation as an Oxidant for the Preparation of Halogenated Hydrocarbons (PDF). McMaster University. pp. 42, 99–145. Retrieved 4 Oct 2014. 
2. 1 2 Eisenberg, Max; Darryl D. DesMarteau (1970). "The reaction of xenon difluoride with some strong oxy-acids". Inorganic and Nuclear Chemistry Letters 6 (1): 29–34. doi:10.1016/0020-1650(70)80279-3. ISSN 0020-1650. 
3. ↑ Zefirov, N. S; Gakh, A. A.; Zhdankin, V. V.; Stang, P. J. (1991). "Interaction of Fluoroxenonium Triflate, Fluorosulfate, and Νitrate with Alkenes. Stereochemical Evidence for the Electrophilic Noble Gas Cation Addition to the Carbon-Carbon Double Bond". J. Org. Chem 56: 1416–1418. 
4. ↑ Atta-ur-Rahman (2006-01-01). Advances in Organic Synthesis: Modern Organofluorine Chemistry-Synthetic Aspects. Bentham Science Publishers. p. 78. ISBN 9781608051984. Retrieved 5 October 2014. 
5. ↑ Moran, Matthew D.; David S. Brock; Hélène P. A. Mercier; Gary J. Schrobilgen (2010). "Xe3OF3+, a Precursor to a Noble-Gas Nitrate; Syntheses and Structural Characterizations of FXeONO2, XeF2·HNO3, and XeF2·N2O4". Journal of the American Chemical Society 132 (39): 13823–13839. doi:10.1021/ja105618w. ISSN 0002-7863. PMID 20843046.