Reactivity of Carbenes and Related Compounds towards Molecular Nitrogen

Article abstract of DOI:10.1002/hlca.19850680534

The thermal N2 exchange of a number of 15N-labelled diazo compounds was studied in solution.The compounds involved were 3-diazo-1-methylindolin-2-one (1), 9-diazafluorene (2), 5-diazo-1,3-cyclopentadiene-1,2,3,4-tetracarbonitrile (3), 2-diazo-2H-imidazole-4,5-dicarbonitrile (4), 4-diazocyclohexa-2,5-dienone (5), and the conjugate acids of 4 and 5, namely 4,5-dicyano-1H-imidazole-2-diazonium ion (6) and 4-hydroxybenzenediazonium ion (7).Only 1, 4, 6, and 7 exchange their diazo group with 'external' molecular N2.The results are explained on the hypothesis that only organic species which have an empty ? orbital and which are effective in ? electron back-donation are able to react with N2.Thus, reaction with carbenes is likely to occur only if the carbene is in the ¹A₂ singlet state and if its electrophilicity is high.