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

Abstract

AbstractWe 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.