Reactivity of 3- and 4-pyridinylnitrene-n-oxide radical anions

• We have examined the ion–molecule reactions of pyridinylnitrene-n-oxide anions.
• CS2 reacts at the nitrene nitrogen in 3-pyridinylnitrene-n-oxide anion.
• With 4-pyridinylnitrene-n-oxide anion, CS2 reacts at both the nitrene N and at the O.
• Resonance interaction makes the n-oxide more reactive in the 4-isomer.

Ion–molecule reactions in a flowing afterglow are used to examine the electronic structure of 3- and 4-pyridinylnitrene-n-oxide radical anions. Reactions with nitric oxide are generally similar to those reported previously for other aromatic nitrene radical anions. In particular, phenoxide formation by nitrogen–oxygen exchange is observed with both isomers. Oxygen atom abstraction by NO is also observed with both isomers. Very significant differences in the reactivity are observed in the reactions of the two isomers with carbon disulfide. The reactivity of the 3-n-oxide isomer with CS2 is similar to that observed previously for nitrene radical anions, and reactions of the n-oxide moiety are not observed, similar to what is expected based on solution chemistry. The 4-n-oxide isomer, however, undergoes many reactions, including oxygen atom and oxygen ion transfer and sulfur–oxygen exchange, that involve the n-oxide oxygen. The increased reactivity of the oxygen is attributed to increased charge density at the oxygen due to pi electron donation of the nitrene anion in the para position.

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