Perfluoro-2,2 -diazaheptafulvalene

Banks and co-workers found that gas-phase pyrolysis of pentafluorophenyl azide yields a diazaheptafulvalene (Scheme 16).50 The formation of the product was viewed as dimerization of the perfluoro analogue of 4b, although it is possible that it could, instead, have been formed by dimerization of the corresponding cyclic ketenimine. 

The formation of seven-membered ring intermediates has been ascertained by the isolation of a dimer, perfluoro-2,7 -diazaheptafulvalene, from the pyrolysis of azidopentafluorobenzene [R. E. Banks, N. D. Venayak, and T. A. Hamor, Chem. Commun., 900 (1980)]. 

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