Pentazoles

The synthesis and isolation of N5+ salts as the third homoleptic polynitrogen species that can be isolated and handled in bulk invigorated the chemistry of polynitrogen compounds. The high energy content of polynitrogen compounds makes them ideal candidates for energetic materials. The pentazole system received special attention because several pentazole compounds are known that can be isolated and handled. Computations predict that the pentazole anion could be another polynitrogen species that can be synthesized in bulk. In the last decade, computations have aimed to predict which pentazole species are the most stable. In general, electron-donating substituents increase the decomposition barrier of the pentazole compounds. New pentazole compounds like tetrazolylpentazole, where the pentazole ring system is attached to a five-membered ring system, and the dipentazole, 1,4-bis(p-pentazolylphenyl)butane, were identified. The mechanism of the synthesis and the mechanism of decomposition of phenylpentazole were determined by a combined NMR spectroscopical and theoretical study. Attempts to cleave the pentazole ring system from phenylpentazole compounds with mass spectrometry techniques were successful but as yet free pentazole or the pentazolate anion have not been isolated.