| Abstract
| - The origins of the lengthening of the N−F bonds of FNO2 and FNO relative to that of NH2F are examinedvia STO-6G valence bond calculations. The calculations were parametrized to reproduce approximately theUHF/cc-pVQZ molecular orbital estimates for the nitrogen and oxygen spin densities of NO2 and NO. Thisprocedure was used in a recent valence-bond study of asym N2O3. The results of the calculations show thatthe N−F lengthening for FNO2 arises from the delocalization of oxygen lone-pair electrons into the AOs ofthe N−F σ bond, whereas this effect and the presence of a “bent” N−F σ bond are primarily responsible forthe N−F lengthening in FNO. For comparison with the experimental geometries of FNO2, FNO, and NH2F,B3LYP/6-31+G(d) molecular orbital estimates of their geometries and those for related systems are reported.Consideration is also given to a spin-coupled valence-bond representation of the electronic structure of FNO2,and a valence-bond representation for the reaction FNO2 + O3 → FNO + 2O2 is provided via the use ofincreased-valence structures for the reactants.
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