Cation
The cyclic pentazolium cation (N5+) is not known due to its probable antiaromatic character; whereas the open chained pentazenium cation (N5+) is known. The mass spectrometer signal for the pentazolide anion (N5-) has been detected from the decomposition of substituted phenyl pentazoles. There was a first report of the synthesis of pentazole and pentazole anion in solution as evidenced by their 15N isotope labeled azide product, but the evidence for the formation of pentazole anion was disputed. Later experiments that involved the detailed analysis of decomposition products demonstrated the generation of pentazole. The experimental conclusions were supported by high level theoretical calculations. However, pentazole is not expected to last longer than a few seconds in aqueous solution without the aid of complexing agents. The discovery of pentazoles spurred attempts to create all-nitrogen salts, which should be highly potent propellants for space travel.
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