Silicon tetraazide

Tetraazidosilan

A white crystalline solid

Soluble in diethyl ether and benzene

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Silicon tetraazide is a thermally unstable silicon-nitrogen compound having a nitrogen content of 85.7 %. The high-energy substance tends to a spontaneous explosive decomposition and has so far been characterized only in solution. Another coordination to hexacoordinate structure as in Hexaazidosilicaten [Si (N3 ) 6] 2 -, or adducts with bivalent ligand Si ( N3) 4L2 leads to relatively stable, crystalline solids which can be handled normally at room temperature.

Representation and extraction

The synthesis of silicon tetraazide achieved by the reaction of silicon tetrachloride with sodium azide in benzene solution.

The reaction of silicon tetrachloride with an excess of sodium azide at room temperature in acetonitrile gives the first Natriumhexaazidosilicat, which can be converted by addition of the divalent ligand such as 2,2 ' -bipyridine and 1,10- phenanthroline in a stable silicon tetraazide adducts. Other bases such as pyridine and tetramethylethylenediamine not react with the Hexaazidosilicatanion.

Another representation of a bis ( triphenylphosphine) iminiumhexaazidosilicatsalzes ( ( PPN) 2 Si (N3 ) 6, [ Ph3P = NPPh3 ] [Si (N3 ) 6] ) by the reaction of bis ( triphenylphosphine ) iminiumazid ( PPNN3, [ Ph3P = NPPh3 ] N3 ) with silicon tetrachloride in acetonitrile.

Properties

Silicon tetraazide is a white crystalline substance that tends even at 0 ° C to explosive decomposition. The pure substance, but also with Siliciumchloridtriazid and Siliciumdichloriddiazid contaminated samples can apparently explode without external cause, for example, in storage spontaneous. The compound is susceptible to hydrolysis. The substance is soluble in diethyl ether and benzene.

The addition compound of 2,2 '-bipyridine is much more stable. Here, a melting point of 212 ° C with a melting enthalpy of 110 J · g -1 is observed. The DSC measurement shows from 265 ° C a strongly exothermic decomposition with a heat of decomposition of -2400 J · g -1. A similar behavior shows the addition compound with 1,10- phenanthroline. The incurred as Hemiacetonitrilsolvat connection is around 100 ° C from the bound solvent, then shows a DSC measurement from 240 ° C a strongly exothermic decomposition with a heat of decomposition of -2300 J · g -1. The decomposition heats are higher than those of sodium azide with -800 J · g -1, but still below the values ​​for conventional explosives like RDX with -4500 J · g -1. The addition compounds are stable in solution. As a result of IR Us 1H NMR spectroscopic data is no dissociation in Siliziumtetraazid and 2,2 ' -bipyridine or 1,10- phenanthroline. Bis (triphenylphosphine) iminiumhexaazidosilicatsalz ( (PPN) 2Si (N3 ) 6) is also relatively stable. The compound melts at 214 ° C, and shows, in a DSC measurement at 250 ° C, a decomposition reaction. A coupled with a mass spectrometer, thermogravimetric investigation revealed as decomposition products nitrogen, silicon tetraazide and hydrazoic acid.

Use

A practical use of free silicon tetraazide is excluded because of the high instability. In solution, the substance still offers an ideal starting material for the synthesis of nitrogen-rich compounds. An application as an adjuvant in the preparation of polyolefin polymers were patentiert.Die substantially stable adducts can be used as energetic compounds or as initiating explosives in replacement of the lead azide.