Pentazenium tetraazidoborate
# Pentazenium tetraazidoborate

Pentazenium tetraazidoborate is an extremely unstable chemical compound with the formula $N_5[B(N_3)_4].$ 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%).

## Production and properties

The production of $N_5[B(N_3)_4]$ requires a multi-step synthesis, first, hydrazoic acid and sodium borohydride is reacted in diethyl ether at -78 °C to produce sodium tetraazidoborate (which decomposes at 76 °C):

    $NaBH_4$ + $4HN_3$ → $Na[B(N_3)_4]$ + $4H_2$

The other reactant, pentazenium hexafluoroantimonate, its produced by the reaction of $N_2F^+$ and antimony(V) fluoride. Then, two reactants that are produced are mixed at -64 °C under sulfur dioxide:

    $Na[B(N_3)_4]$ + $N_5SbF_6$ → $N_5[B(N_3)_4]$ + $NaSbF_6↓$

to produce the pentazenium tetraazidoborate. If heated, it decomposes into nitrogen gas and boron triazide; the boron triazide further decomposes into boron nitride and nitrogen. The overall reaction is the following:

    $N_5[B(N_3)_4]$ → $8N_2$ + BN

The compound is extremely sensitive, an attempted Raman spectroscopy of a 500 mg sample of the compound resulted in an explosion.

