Boron triazide

Structural formula
General
Surname	Boron triazide
other names	Triazidoborane
Molecular formula	B (N 3 ) 3
Brief description	colorless crystals
External identifiers / databases
CAS number 21884-15-1 Wikidata Q24287578
properties
Molar mass	136.87 g mol −1
Physical state	firmly
solubility	soluble in diethyl ether
safety instructions
GHS hazard labeling no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Boron triazide (or triazidoborane) is a thermally unstable boron - nitrogen compound with a nitrogen content of 92.1%. Formally it is the triazido derivative of borane . The substance belongs to the group of covalent inorganic azides . The high-energy substance tending to spontaneously explosive decomposition was first described in 1954 by Egon Wiberg and Horst Michaud from the University of Munich .

Extraction and presentation

The first preparation was carried out by adding diborane to a solution of hydrazoic acid in diethyl ether in the temperature range between −20 ° C and −10 ° C. The synthesis proceeds via the intermediate compounds monoazidoborane BH ₂ N ₃ and diazidoborane BH (N ₃ ) ₂ .

${\displaystyle \mathrm {B_{2}H_{6}+6\,HN_{3}\rightarrow 2\,B(N_{3})_{3}+6\,H_{2}} }$

The connection can also be obtained by passing boron tribromide vapor over solid silver azide in a high vacuum.

${\displaystyle \mathrm {BBr_{3}+3\,AgN_{3}\rightarrow B(N_{3})_{3}+3\,AgBr} }$

A similar gas-phase synthesis is achieved by the spontaneous reaction of boron trichloride with hydrogen azide .

${\displaystyle \mathrm {BCl_{3}+3\,HN_{3}\rightarrow B(N_{3})_{3}+3\,HCl} }$

properties

The compound forms colorless crystals that are only stable at lower temperatures. Explosive decomposition can take place above −35 ° C. Boron triazide generated in the gas phase decomposes at room temperature within 60 minutes with elimination of nitrogen to form boron nitrides with the composition BN ₃ or BN, which are deposited on the reactor wall. These reactions can also be realized photochemically by irradiation with UV light in the absorption range of the compound around 230 nm.

${\displaystyle \mathrm {B(N_{3})_{3}\rightarrow BN_{3}+3\,N_{2}} }$

${\displaystyle \mathrm {B(N_{3})_{3}\rightarrow BN+4\,N_{2}} }$

In the presence of water, hydrolysis occurs to form hydrazoic acid and boron trioxide .

${\displaystyle \mathrm {2\,B(N_{3})_{3}+3\,H_{2}O\rightarrow 6\,HN_{3}+B_{2}O_{3}} }$

The reaction with azides , such as sodium azide or lithium azide, gives the corresponding tetraazidoborate complexes.

${\displaystyle \mathrm {B(N_{3})_{3}+NaN_{3}\rightarrow NaB(N_{3})_{4}} }$

${\displaystyle \mathrm {B(N_{3})_{3}+LiN_{3}\rightarrow LiB(N_{3})_{4}} }$

The tetraazidoboric acid HB (N ₃ ) ₄ on which the tetraazidoborates are based can be obtained in the free state at low temperatures below −60 ° C.

use

Use as a high-energy substance is not relevant because of its poor stability. In contrast, the derived tetraazidoborates or adducts with bases, such as quinoline , pyrazine or 2,2,6,6-tetramethylpiperidine, are more interesting. The compound is interesting as a starting material due to decomposition from the gas phase for coating surfaces with boron nitrides.

Individual evidence

1. ^ ^{A b c d e f g} E. Wiberg, H. Michaud: On the knowledge of a boron triazide. In: Z. Naturforsch. B . Volume 9, 1954, pp. 497-499. doi: 10.1515 / znb-1954-0715 (accessed via De Gruyter Online).
2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
3. ↑ F. Lui, X. Zeng, J. Zhang, L. Meng, S. Zhang, M. Ge, D. Wang, D. Kam Wah Mok, F. Chau: A simple method to generate B (N ₃ ) ₃ . In: Chem. Phys. Lett. Volume 419, 2006, pp. 213-216, doi: 10.1016 / j.cplett.2005.11.082 .
4. ↑ ^{a b c d} R. L. Mulinax, GS Okin, RD Coombe: Gas Phase Synthesis, Structure, and Dissociation of Boron Triazide. In: J. Phys. Chem. Vol. 99, 1995, pp. 6294-6300, doi: 10.1021 / j100017a007 .
5. ↑ ^{a b} I. A. Al-Jihad, B. Liu, CJ Linnen, JV Gilbert: Gereration of NNBN via Photolysis of B (N ₃ ) ₃ in Low-Temperature Argon Matrices: IR spectra and from Initio Calculations. In: J. Phys. Chem. A . Volume 102, 1998, pp. 6220-6226, doi: 10.1021 / jp9812684 .
6. ↑ MJ Travers, JV Gilbert: UV Absorption Spectra of Intermediates Generated via Photolysis of B (N ₃ ) ₃ , BCl (N ₃ ) ₂ , and BCl ₂ (N ₃ ) in Low-Temperature Argon Matrices. In: J. Phys. Chem. A . Volume 104, 2000, pp. 3780-3785, doi: 10.1021 / jp993939j .
7. ↑ E. Wiberg, H. Michaud: On the knowledge of an ether-soluble lithium borazide LiB (N ₃ ) ₄ . In: Z. Naturforsch. B . Volume 9, 1954, p. 499, doi: 10.1515 / znb-1954-0716 (accessed via De Gruyter Online).
8. ↑ W. Fraenk, T. Habereder, A. Hammerl, TM Klapötke, B. Krumm, P. Mayer, H. Nöth, M. Warchhold: Highly Energetic Tetraazidoborate anion and Boron Triazide Adducts. In: Inorg. Chem. Vol. 40, 2001, pp. 1334-1340, doi: 10.1021 / ic001119b .

literature

• W. Fraenk, TM Klapötke : Recent Developments in the Chemistry of Covalent Main Group Azides. In: G. Meyer, D. Naumann, L. Wesemann (Eds.): Inorganic Chemistry Highlights. Wiley-VCH Verlag, 2002, ISBN 3-527-30265-4 , pp. 259-265.