Tetranitratoborate is an anion composed of boron with four nitrate groups. It has formula . It can form salts with large cations such as
tetramethylammonium
Tetramethylammonium (TMA) or (Me4N+) is the simplest quaternary ammonium cation, consisting of four methyl groups attached to a central nitrogen atom, and is isoelectronic with neopentane. It is positively charged and can only be isolated in asso ...
nitratoborate,
or
tetraethylammonium tetranitratoborate.
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, ,
which has resisted attempts to make it; if it exists, it is unstable above −78 °C.
Other related ions are the slightly more stable
tetraperchloratoborates, with perchlorate groups instead of nitrate, and
tetranitratoaluminate with the next atom down the periodic table, aluminium instead of boron ().
Formation
Tetramethylammonium chloride
Tetramethylammonium chloride is one of the simplest quaternary ammonium salts, with four methyl groups tetrahedrally attached to the central N. The chemical formula (CH3)4N+Cl− is often abbreviated further as Me4N+Cl−. It is a hygroscopic colo ...
reacts with
to make . Then the tetrachloroborate is reacted with
at around −20 °C to form tetramethylammonium nitratoborate, and other gases such as
and
.
Another mechanism to make tetranitratoborate salts is to shake a metal nitrate with in chloroform at 20 °C for several days.
Trichloronitratoborate is an unstable intermediate.
:
:
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 ''v''
4. Also prominent is 1,297 and 1,311 cm
−1 attributed to ''v''
1, with these vibrations due to the nitrate bonded via one oxygen.
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.
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
Dimethylformamide is an organic compound with the formula ( CH3)2NC(O)H. Commonly abbreviated as DMF (although this initialism is sometimes used for dimethylfuran, or dimethyl fumarate), this colourless liquid is miscible with water and the majo ...
.
It reacts with liquid
sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
.
At room temperature tetramethylammonium nitratoborate is stable for months. It does not explode with impact.
Alkali metal tetranitratoborates are unstable at room temperature and decompose.
1-Ethyl-3-methyl-imidazolimium tetranitratoborate was discovered in 2002. It is an ionic liquid that turns solid at −25 °C.
References
{{boron compounds
Nitrates
Boron compounds
Borates
Anions