FN+Cl Ions from Ionized F2NCl: a Computational Investigation on the Structure and Reactivity toward H2O

We have used various ab initio methods and basis sets to ascertain that the FN⁺Cl cation has a singlet ground state, ¹A′, which is more stable than the triplet state ³A″ by ca. 30 kcal mol^?1. We have subsequently used the Gaussian‐3 (G3) theory to explore the potential‐energy profile for the reaction between singlet FN⁺Cl and H₂O. The process commences by the effortless formation of a FN⁺Cl/H₂O complex, which, in principle, can undergo several alternative processes, including isomerization to N‐protonated FN(Cl)OH, 1,2‐elimination of HX (X=F or Cl), and 1,1‐loss of H₂. However, the energy barriers of all these processes are invariably larger than the energy (+18.1 kcal mol^?1) required for the formation of FN⁺Cl/H₂O from FN⁺Cl and H₂O, thus suggesting that, under gas‐phase thermal conditions, FN⁺Cl should be essentially unreactive toward H₂O. Comparing these theoretical findings with those concerning the reaction between FN⁺H, ClN⁺H, F₂N⁺, and H₂O, the reactivity order FN⁺H>F₂N⁺>ClN⁺H>FN⁺Cl, was derived, which parallels the trend we recently found by G2MS calculations concerning the Lewis acidity of these ions. This suggests the conceivable occurrence of correlations between the reactivity and thermochemical properties of these simple halonitrenium ions.