Lewis acid-base behavior of hypervalent halogen fluorides in gas phase

Abstract

Theoretical studies on Lewis acid-base behavior of hypervalent halogen fluorides, F3X and F5X (X = Cl, Br, I) have been instrumental in guiding this work. We have also examined whether the hole-lump concept explains the formation of the F5X∙∙∙CO complexes. Calculations of proton affinities (PA) and gas-phase basicity (GB) on hypervalent halogen fluorides show that F3X and F5X molecules can act as Lewis bases in gas phase. Moreover, theoretical calculations indicate that F3X and F5X molecules can act as Lewis acids forming stable complexes with a Lewis base as CO. The quantum theory of atoms in molecules (QTAIM) shows that the electrostatic interaction between the lone pair of the Lewis base (CO) and nucleus of the hypervalent halogen atom (X) plays a key role in stabilizing and determining the optimal geometry of the F5X∙∙∙CO complexes, as in conventional XBs. The localized molecular orbital energy decomposition analysis (LMOEDA) reveals that electrostatic component plays an important role in the stability of the FnX···CO complexes.