Polynitrogen isolable ions

N+ and N+, have been observed only as free gaseous or matrix-isolated ions or radicals. The only polynitrogen species synthesized on a macroscopic scale thus far is the pentanitrogen cation Nj by Christe and co-workers in 1999. 

The experimental aspect will be presented first, to emphasize the dearth of such results. We can put polynitrogens into four classes neutral molecules, extended-molecular allotropes, isolable ions, and ephemeral ions mainly of mass-spectrometric interest. This fourth class will not be discussed. 

Isolable ions, i.e. polynitrogen cations and anions, have met with more synthetic success than have neutral molecules. Although there is experimental evidence (above) for neutral N4 and Ng species, none have been isolated in contrast, the azide ion Ns" has been known for well over a century, an N5 cation has been made in macroscopic amounts, and an N5 anion has been detected. 

The synthesis of the pentanitrogen cation (6) marks a milestone in polynitrogen chemistry [32], because this is only the second poly nitrogen to have been actually isolated, as (hstinct from just spectroscopically detected. Salts of the azide ion were first reported in 1890 [27], and salts of the pentanitrogen cation in 1999 [18], The hiatus suggests that the synthesis of polynitrogens involves problems. The first Ns salt used the hexafluoroarsenate counterion ... 

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