Silicon tetraazide

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Silicon tetraazide
Silicon tetraazide 01.svg
Silicon-tetraazide-3D-spacefill.png
Names
Other names
Tetraazidosilane
Identifiers
3D model (JSmol)
ChemSpider
PubChem CID
  • InChI=1S/N12Si/c1-5-9-13(10-6-2,11-7-3)12-8-4
    Key: SZJFGTWFLXTOHF-UHFFFAOYSA-N
  • [N-]=[N+]=N[Si](N=[N+]=[N-])(N=[N+]=[N-])N=[N+]=[N-]
Properties
Si(N3)4
Molar mass 196.1659 g/mol
AppearanceWhite crystals
Melting point 212 °C (414 °F; 485 K)
Reacts
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Silicon tetraazide is a thermally unstable binary compound of silicon and nitrogen with a nitrogen content of 85.7% (by molar mass). This high-energy compound combusts spontaneously and can only be studied in a solution. [1] [2] [3] A further coordination to a six-fold coordinated structure such as a hexaazidosilicate ion [Si(N3)6]2− [4] or as an adduct with bicationic ligands Si(N3)4·L2 [2] will result in relatively stable, crystalline solids that can be handled at room temperature.

Contents

Preparation

Silicon tetraazide is synthesized by conversion of silicon tetrachloride with sodium azide in benzene. [1] [3]

Silicon tetraazide synthesis 02.svg

The reaction of silicon tetrachloride with an excess of sodium azide at room temperature in acetonitrile will result in the formation of sodium hexaazidosilicate (Na2[Si(N3)6]) which by adding ligands such as 2,2′-bipyridine and 1,10-phenanthroline will result in stable silicon tetraazide adducts. [2] Other bases such as pyridine and tetramethylethylenediamine will not react with the hexaazidosilicate ion. [2]

Silicon tetraazide synthesis 01.svg

Another preparation of a bis(triphenylphosphine)iminium hexaazidosilicate salt [(Ph3P)2N]2[Si(N3)6] is possible by conversion of bis(triphenylphosphine)iminium azide [(Ph3P)2N]N3 with silicon tetrachloride in acetonitrile, where Ph is phenyl. [4]

Properties

Silicon tetraazide is a white crystalline compound that will detonate at even 0 °C. [1] The pure compound, and also silicon chloride triazide SiCl(N3)3 and silicon dichloride diazide SiCl2(N3)2 contaminated samples, can detonate spontaneously without clear cause. [5] The compound is susceptible to hydrolysis. [3] It is soluble in diethylether and benzene. [1]

The addition compound with 2,2′-bipyridine is much more stable. A melting point of 212 °C with a melting enthalpy of 110 J/g is recorded. The DSC measurement shows at 265 °C a sharp exothermic reaction with an enthalpy of −2400 J/g. Similar results are found for the addition compound with 1,10-phenanthroline. As the hemiacetonitrile solvatated isolated compound expels solvent at 100 °C, and shows then in the DSC measurement from 240 °C onwards a strong exothermic reaction with a generated heat of 2300 J/g. [2] The enthalpies are higher than that of sodium azide with −800 J/g, [6] but still lower than the values encountered with classic explosives such as RDX with −4500 J/g. [2] The addition compounds are stable in solution. It can be concluded from IR-spectroscopy and proton NMR data that no dissociation occurs in silicon tetraazide and 2,2'-bipyridine or for example 1,10-phenanthroline. [2] The bis(triphenylphosphino)iminium hexaazidosilicate salt [(Ph3P)2N]2[Si(N3)6] on the other hand is relatively stable. The compound melts at 214 °C and shows in the DSC measurement at 250 °C a reaction. [4] One mass spectrometry coupled thermogravimetric analysis investigation indicated as reaction products nitrogen, silicon tetraazide and hydrazoic acid. [4]

Applications

A practical application of free silicon tetraazide is unlikely due to the high instability. In solution the compound has potential uses as raw material for nitrogen-rich materials. [2] One application as reagent in the manufacture of polyolefins has been patented. [7] The stabilized adducts can serve as energetic compounds as a replacement for lead azide. [2]

Related Research Articles

In chemistry, azide is a linear, polyatomic anion with the formula N−3 and structure N=N+=N. It is the conjugate base of hydrazoic acid HN3. Organic azides are organic compounds with the formula RN3, containing the azide functional group. The dominant application of azides is as a propellant in air bags.

<span class="mw-page-title-main">Nitrous acid</span> Chemical compound

Nitrous acid is a weak and monoprotic acid known only in solution, in the gas phase and in the form of nitrite salts. Nitrous acid is used to make diazonium salts from amines. The resulting diazonium salts are reagents in azo coupling reactions to give azo dyes.

<span class="mw-page-title-main">Sodium azide</span> Chemical compound

Sodium azide is an inorganic compound with the formula NaN3. 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 an ionic substance, is highly soluble in water, and is very acutely poisonous.

<span class="mw-page-title-main">Terpyridine</span> Chemical compound

Terpyridine is a heterocyclic compound derived from pyridine. It is a white solid that is soluble in most organic solvents. The compound is mainly used as a ligand in coordination chemistry.

<span class="mw-page-title-main">1,10-Phenanthroline</span> Heterocyclic organic compound

1,10-Phenanthroline (phen) is a heterocyclic organic compound. It is a white solid that is soluble in organic solvents. The 1,10 refer to the location of the nitrogen atoms that replace CH's in the hydrocarbon called phenanthrene.

<span class="mw-page-title-main">Triphenylphosphine</span> Chemical compound

Triphenylphosphine (IUPAC name: triphenylphosphane) is a common organophosphorus compound with the formula P(C6H5)3 and often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature. It dissolves in non-polar organic solvents such as benzene and diethyl ether.

<span class="mw-page-title-main">Tetrasulfur tetranitride</span> Chemical compound

Tetrasulfur tetranitride is an inorganic compound with the formula S4N4. This gold-poppy coloured solid is the most important binary sulfur nitride, which are compounds that contain only the elements sulfur and nitrogen. It is a precursor to many S-N compounds and has attracted wide interest for its unusual structure and bonding.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most common oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

<span class="mw-page-title-main">Bis(triphenylphosphine)iminium chloride</span> Chemical compound

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [( 3P)2N]Cl, often abbreviated [(Ph3P)2N]Cl, where Ph is phenyl C6H5, or even abbreviated [PPN]Cl or [PNP]Cl or PPNCl or PNPCl, where PPN or PNP stands for (Ph3P)2N. This colorless salt is a source of the [(Ph3P)2N]+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. [(Ph3P)2N]+ is a phosphazene.

<span class="mw-page-title-main">Tetraazidomethane</span> Chemical compound

Tetraazidomethane, C(N3)4, is a colorless, highly explosive liquid. Its chemical structure consists of a carbon atom covalently bonded to four azide functional groups.

The Chichibabin reaction is a method for producing 2-aminopyridine derivatives by the reaction of pyridine with sodium amide. It was reported by Aleksei Chichibabin in 1914. The following is the overall form of the general reaction:

<span class="mw-page-title-main">Potassium azide</span> Chemical compound

Potassium azide is the inorganic compound having the formula KN3. It is a white, water-soluble salt. It is used as a reagent in the laboratory.

<span class="mw-page-title-main">Brookhart's acid</span> Chemical compound

Brookhart's acid is the salt of the diethyl ether oxonium ion and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BAr′4). It is a colorless solid, used as a strong acid. The compound was first reported by Volpe, Grant, and Brookhart in 1992.

<span class="mw-page-title-main">4-Chlorophenyl azide</span> Chemical compound

4-Chlorophenyl azide is an organic aryl azide compound with the chemical formula C6H4ClN3. The geometry between the nitrogen atoms in the azide functional group is approximately linear while the geometry between the nitrogen and the carbon of the benzene is trigonal planar.

<span class="mw-page-title-main">Cyanogen azide</span> Chemical compound

Cyanogen azide, N3CN or CN4, is an azide compound of carbon and nitrogen which is an oily, colourless liquid at room temperature. It is a highly explosive chemical that is soluble in most organic solvents, and normally handled in dilute solution in this form. It was first synthesised by F. D. Marsh at DuPont in the early 1960s. There had been earlier claims of discovering it as a crystalline solid, which were incorrect.

<span class="mw-page-title-main">Boron triazide</span> Chemical compound

Boron triazide, also known as triazidoborane, is a thermally unstable compound of boron and nitrogen with a nitrogen content of 92.1 %. Formally, it is the triazido derivative of borane and is a covalent inorganic azide. 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.

An organic azide is an organic compound that contains an azide functional group. Because of the hazards associated with their use, few azides are used commercially although they exhibit interesting reactivity for researchers. Low molecular weight azides are considered especially hazardous and are avoided. In the research laboratory, azides are precursors to amines. They are also popular for their participation in the "click reaction" between an azide and an alkyne and in Staudinger ligation. These two reactions are generally quite reliable, lending themselves to combinatorial chemistry.

Transition metal complexes of 2,2'-bipyridine are coordination complexes containing one or more 2,2'-bipyridine ligands. Complexes have been described for all of the transition metals. Although few have any practical value, these complexes have been influential. 2,2'-Bipyridine is classified as a diimine ligand. Unlike the structures of pyridine complexes, the two rings in bipy are coplanar, which facilitates electron delocalization. As a consequence of this delocalization, bipy complexes often exhibit distinctive optical and redox properties.

<span class="mw-page-title-main">Pentazenium tetraazidoborate</span> Chemical compound

Pentazenium tetraazidoborate is an extremely unstable chemical compound with the formula N5[B(N3)4]. It is a white solid that violently explodes at room temperature. This compound has a 95.7% nitrogen content which is the second highest known of a chemical compound, exceeding even that of ammonium azide (93.3%) and 1-diazidocarbamoyl-5-azidotetrazole (89.1%), being surpassed only by hydrazoic acid (97.7%).

Homoleptic azido compounds are chemical compounds in which the only anion or ligand is the azide group, -N3. The breadth of homoleptic azide compounds spans nearly the entire periodic table. With rare exceptions azido compounds are highly shock sensitive and need to be handled with the upmost caution. Binary azide compounds can take on several different structures including discrete compounds, or one- two, and three-dimensional nets, leading some to dub them as "polyazides". Reactivity studies of azide compounds are relatively limited due to how sensitive they can be. The sensitivity of these compounds tends to be correlated with the amount of ionic or covalent character the azide-element bond has, with ionic character being far more stable than covalent character. Therefore, compounds such as silver or sodium azide – which have strong ionic character – tend to possess more synthetic utility than their covalent counterparts. A few other notable exceptions include polymeric networks which possess unique magnetic properties, group 13 azides which unlike most other azides decompose to nitride compounds (important materials for semiconductors), other limited uses as synthetic reagents for the transfer for azide groups, or interest in high energy density materials.

References

  1. 1 2 3 4 Wilberg, E.; Michaud, H.: Z. Naturforsch. B 9 (1954) S. 500.
  2. 1 2 3 4 5 6 7 8 9 Portius, Peter; Filippou, Alexander C.; Schnakenburg, Gregor; Davis, Martin; Wehrstedt, Klaus-Dieter (2010). "Neutrale Lewis-Basen-Addukte des Siliciumtetraazids". Angewandte Chemie. 122 (43): 8185–8189. Bibcode:2010AngCh.122.8185P. doi:10.1002/ange.201001826.
  3. 1 2 3 Gmelins Handbook of Inorganic Chemistry, 8th Edition, Silicon Supplement Volume B4, Springer-Verlag 1989, S. 46.
  4. 1 2 3 4 Filippou, Alexander C.; Portius, Peter; Schnakenburg, Gregor (2002). "The Hexaazidosilicate(IV) Ion: Synthesis, Properties, and Molecular Structure". Journal of the American Chemical Society. 124 (42): 12396–12397. doi:10.1021/ja0273187. PMID   12381165.
  5. Bretherick's Handbook of Reactive Chemical Hazards, 7th revised edition, Academic Press 2006, ISBN   978-0-12-372563-9
  6. T. Grewer: Thermal Hazards of Chemical Reactions, Industrial Safety Series 4, Elsevier 1994.
  7. Nomura, M.; Tomomatsu, R.; Shimazaki, T.: EP 206 034 (1985) pdf-Download