Electron transfer chemistry of some unusual nitrogen compounds: From stable nitrenium ions to the corresponding nitrogen centered radicals

Nitrogen-centered radicals (1b^., 2b^., 3b^., 4b^.) have been generated upon electron transfer from the corresponding stable nitrenium ions (1b⁺, 2b⁺, 3b⁺, 4b⁺) and characterized by electrochemistry and simultaneous spectro-electrochemistry. Reactivity of the radicals is strongly influenced by the substituents attached to the two nitrogen atoms that are directly linked to the ion nitrenium center. While 1b^. and 2b^. are stable on the timescale of the electrochemical experiment, 3b^. and 4b^. have half-lifetimes of ca. 1.2-1.25 and 0.9-1 μs, respectively, in acetonitrile, as determined with ultramicroelectrodes. Redox properties of the nitrenium ion/radical couples and relative stability of the radicals are discussed in light of both experimental results and ab initio calculations.