Chemistry:Tetranitratoborate

Tetranitratoborate is an anion composed of boron with four nitrate groups. It has formula [B(NO
3)
4]−
. It can form salts with large cations such as tetramethylammonium nitratoborate,^[1] or tetraethylammonium tetranitratoborate.^[2] The ion was first discovered by C. R. Guibert and M. D. Marshall in 1966 after failed attempts to make neutral (non-ionic) boron nitrate, B(NO
3)
3,^[1] which has resisted attempts to make it; if it exists, it is unstable above −78 °C.^[2]

Other related ions are the slightly more stable tetraperchloratoborates, with perchlorate groups instead of nitrate, and tetranitratoaluminate^[3] with the next atom down the periodic table, aluminium instead of boron ([Al(NO
3)
4]−
).

Formation

Tetramethylammonium chloride reacts with BCl
3 to make [N(CH
3)
4]+
[BCl
4]−
. Then the tetrachloroborate is reacted with N
2O
4 at around −20 °C to form tetramethylammonium nitratoborate, and other gases such as NO
2Cl and Cl
2.^[2]

Another mechanism to make tetranitratoborate salts is to shake a metal nitrate with BCl
3 in chloroform at 20 °C for several days. Trichloronitratoborate [BCl
3(NO
3)]−
is an unstable intermediate.

M+
NO−
3 + BCl
3 → M+
[BCl
3(NO
3)]−

4 M+
[BCl
3(NO
3)]−
→ 3 M+
[BCl
4]−
+ M+
[B(NO
3)
4]−
^[4]

Properties

The infrared spectrum of tetramethylammonium nitratoborate includes a prominent line at 1,612 cm⁻¹ with shoulders at 1582 and 1,626 cm⁻¹ attributed to v₄. Also prominent is 1,297 and 1,311 cm⁻¹ attributed to v₁, with these vibrations due to the nitrate bonded via one oxygen.^[1]

The density of tetramethylammonium nitratoborate is 1.555 g·cm⁻³. It is colourless and crystalline. As tetramethylammonium nitratoborate is heated it has some sort of transition between 51 and 62 °C. It decomposes above 75 °C producing gas. Above 112 °C it is exothermic, and a solid is left if it is heated to 160 °C.^[2]

Tetramethylammonium nitratoborate is insoluble in cold water but slightly soluble in hot water. It does not react with water. It also dissolves in liquid ammonia, acetonitrile, methanol, and dimethylformamide.^[1] It reacts with liquid sulfur dioxide.^[1]^[5]

At room temperature tetramethylammonium nitratoborate is stable for months. It does not explode with impact.^[1]

Alkali metal tetranitratoborates are unstable at room temperature and decompose.^[4]

1-Ethyl-3-methyl-imidazolimium tetranitratoborate was discovered in 2002. It is an ionic liquid that turns solid at −25 °C.^[6]

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 Guibert, C. R.; M. D. Marshall (1966). "Synthesis of the Tetranitratoborate Anion". Journal of the American Chemical Society 88 (1): 189–190. doi:10.1021/ja00953a051. ISSN 0002-7863.
↑ ^2.0 ^2.1 ^2.2 ^2.3 Titova, K. V.; V. Ya. Rosolovskii (1970). "Tetraalkylammonium nitratoborates". Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 19 (12): 2515–2519. doi:10.1007/BF00854900. ISSN 0568-5230.
↑ Jones, CJ Bigler (2007). Transition and Main Group Metals Applied to Oxidative Functionalization of Methane and Use as High Oxygen Carriers for Rocket Propellants. p. 139. ISBN 9780549231066. https://books.google.com/books?id=ELjafGhBa3EC&pg=PA139. Retrieved 3 February 2014.
↑ ^4.0 ^4.1 Titova, K. V.; V. Ya. Rosolovskii (1975). "Reaction of nitrates of monovalent cations with BCl₃". Bulletin of the Academy of Sciences of the USSR Division of Chemical Science 24 (10): 2246–2248. doi:10.1007/BF00929774. ISSN 0568-5230.
↑ C.C. Addison; D. Sutton. Progress in Inorganic Chemistry. 8. p. 216.
↑ Jones, C. Bigler; Ralf Haiges; Thorsten Schroer; Karl O. Christe (2006). "Oxygen-Balanced Energetic Ionic Liquid". Angewandte Chemie International Edition 45 (30): 4981–4984. doi:10.1002/anie.200600735. ISSN 1433-7851. PMID 16819744.