Studies of the Reaction Behavior of Nitryl Compounds Towards Azides: Evidence for Tetranitrogen Dioxide, N4O2

The reaction behavior of NaN3, AgN3, and Me3SiN3 towards FNO2, CINO2, NO2SbF6, and NO2BF4 was investigated. At ‐30°C or below in a solvent‐free system sodium azide did not react with CINO2, NO2BF4, or NO2SbF6. Below ‐30°C silver azide did not react either with neat C1NO2. Treatment of Me3SiN3 with pure C1NO2 led to the formation of C1N3, N2O, and Me3SiOSiMe3. A mechanism for this reaction has been proposed. Pure chlorine azide was isolated by fractional condensation and identified by its low‐temperature Raman spectrum (liquid state). The reaction of Cp2Ti(N3)2 with C1NO2 also yielded C1N3 as the only azide‐containing reaction product. Treatment of FNO2 with NaN3 at temperatures as low as ‐78°C always ended in an explosion which was probably due to the formation of FN3 as one of the reaction products. The reaction of NO2SbF6 with NaN3 in liquid CO2 (‐55°C· T· ‐35°C) as the solvent afforded a new azide species which was stable at low temperature in solution only and was investigated by means of low‐temperature Raman spectroscopy. The obtained vibrational data give strong evidence for the presence of tetranitrogen dioxide, N4O2, which can be regarded as nitryl azide (NO2N3). The structure and vibrational frequencies of N4O2 were computed ab initio at correlated level (MP2/6‐31 + G*). In liquid xenon (‐100°C· T· ‐60°C) NaN3 did not react with NO2SbF6. A previous literature report on the preparation of N4O2 could not be established.