Boron triazide, also known as triazidoborane, is a thermally unstable compound of
boron
Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three ...
and
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
with a nitrogen content of 92.1 % (by the
standard atomic weight
The standard atomic weight of a chemical element (symbol ''A''r°(E) for element "E") is the weighted arithmetic mean of the relative isotopic masses of all isotopes of that element weighted by each isotope's abundance on Earth. For example, ...
). Formally, it is the triazido derivative of
borane
Borane is an inorganic compound with the chemical formula . Because it tends to dimerize or form adducts, borane is very rarely observed. It normally dimerizes to diborane in the absence of other chemicals. It can be observed directly as a c ...
and is a covalent inorganic
azide
In chemistry, azide (, ) is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant ...
. The high-energy compound, which has the propensity to undergo spontaneous explosive decomposition, was first described in 1954 by
Egon Wiberg and Horst Michaud of the
University of Munich
The Ludwig Maximilian University of Munich (simply University of Munich, LMU or LMU Munich; ) is a public university, public research university in Munich, Bavaria, Germany. Originally established as the University of Ingolstadt in 1472 by Duke ...
.
Preparation
The first method is by the addition of
diborane
Diborane(6), commonly known as diborane, is the chemical compound with the formula . It is a highly toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has att ...
to a solution of
hydrazoic acid
Hydrazoic acid, also known as hydrogen azide, azic acid or azoimide, This also contains a detailed description of the contemporaneous production process. is a compound with the chemical formula . It is a colorless, volatile, and explosive liquid ...
in
diethyl ether
Diethyl ether, or simply ether, is an organic compound with the chemical formula , sometimes abbreviated as . It is a colourless, highly Volatility (chemistry), volatile, sweet-smelling ("ethereal odour"), extremely flammable liquid. It belongs ...
at a temperature range between −20 °C and −10 °C. This synthesis proceeds via the intermediates monoazidoborane, , and diazidoborane, .
:
The compound can also be obtained by passing
boron tribromide
Boron tribromide, BBr3, is a colorless, fuming liquid compound containing boron and bromine. Commercial samples usually are amber to red/brown, due to weak bromine contamination. It is decomposed by water and alcohols.
Chemical properties
Boron ...
vapor over solid
silver azide
Silver azide is the chemical compound with the chemical formula, formula . It is a silver(I) salt of hydrazoic acid. It forms a colorless crystals. Like most azides, it is a primary explosive.
Structure and chemistry
Silver azide can be prepared ...
in high vacuum.
:
A similar gas-phase synthesis uses the spontaneous reaction of
boron trichloride
Boron trichloride is the inorganic compound with the formula BCl3. This colorless gas is a reagent in organic synthesis. It is highly reactive towards water.
Production and structure
Boron reacts with halogens to give the corresponding trihalides ...
with hydrazoic acid.
:
Properties
The compound forms colorless crystals that are only stable at low temperatures. Above −35 °C, an explosive decomposition may occur.
In the gas phase, generated boron triazide decomposes at
room temperature
Room temperature, colloquially, denotes the range of air temperatures most people find comfortable indoors while dressed in typical clothing. Comfortable temperatures can be extended beyond this range depending on humidity, air circulation, and ...
within 60 minutes via loss of nitrogen gas to form boron nitrides with formulas and
BN. These reactions can also be initiated
photochemically
Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible (400–750&nb ...
by UV radiation in the compounds absorption range at about 230 nm.
:
:
In contact with water, it undergoes hydrolysis to hydrazoic acid and
boron trioxide
Boron trioxide or diboron trioxide is the oxide of boron with the formula . It is a colorless transparent solid, almost always glassy (amorphous), which can be crystallized only with great difficulty. It is also called boric oxide or boria. It h ...
.
:
Reaction with other azides like
sodium azide
Sodium azide is an inorganic compound with the formula . This colorless salt is the gas-forming component in some car airbag systems. It is used for the preparation of other azide compounds. It is highly soluble in water and is acutely poisonou ...
or
lithium azide
Lithium azide is the lithium salt of hydrazoic acid. It is an unstable and toxic compound that decomposes into lithium and nitrogen when heated.
Preparation
It can be prepared by metathesis reaction between sodium azide and lithium nitrate or ...
yields the corresponding tetraazidoborate complexes.
:
:
The parent tetraazidoboric acid, , can be obtained at temperatures lower than −60 °C.
Uses
Due to the low stability, the compound itself is not used as a high-energy substance. However, the tetraazidoborate derivatives and adducts with bases such as
quinoline
Quinoline is a heterocyclic aromatic organic compound with the chemical formula C9H7N. It is a colorless hygroscopic liquid with a strong odor. Aged samples, especially if exposed to light, become yellow and later brown. Quinoline is only sl ...
,
pyrazine
Pyrazine is a heterocyclic aromatic organic compound with the chemical formula C4H4N2. It is a symmetrical molecule with point group D2h. Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a ''"deliquescent crystal or wax-lik ...
or
2,2,6,6-tetramethylpiperidine
2,2,6,6-Tetramethylpiperidine, abbreviated TMP, HTMP, or TMPH, is an organic compound of the amine class. In appearance, it is a colorless liquid and has a "fishy", amine-like odor. This amine is used in chemistry as a hindered base ( hindered am ...
have potential for this usage.
The gas-phase decomposition of the compound is also of interest as a method of coating surfaces with boron nitride.
References
Further reading
*
{{Azides
Azido compounds
Boron–nitrogen compounds
Substances discovered in the 1950s