An electron spin resonance study of the photolysis of azide ions in liquid ammonia: formation of imine radical anions in the presence of alkenes

Abstract

U.v. photolysis of ammonia or ammonia-ethereal solutions containing sodium or tetra-n-butylammonium azide leads to the formation of the diazene radical anion [HNNH]^–˙, which is detectable by e.s.r. spectroscopy. The e.s.r. spectrum of the ammonia-solvated electron is also observed and the primary photochemical process is probably ejection of an electron from N₃^– to give the azido radical N₃˙. Addition of N₃˙ to ammonia and subsequent loss of nitrogen accompanied or followed by a hydrogen shift would give the hydrazyl radical, deprotonation of which gives [HNNH]^–˙. In the presence of mono- or 1,1-di-alkylated ethenes, R¹R²CCH₂, the spectrum of [HNNH]^–˙ is replaced by one assigned to the imine radical anion [R¹R²CH–C(H)NH]^–˙ possible routes for formation of such species following addition of N₃˙ to the alkene are discussed.