Cyclic pi Electron De localization in Fluoroborazines

Abstract

How does the most electronegative atom, fluorine, affect cyclic pi electron delocalization (aromaticity) of an inorganic counterpart of benzene, borazine? Previous studies have shown that N-fluorination decreases the aromatic character, whereas conclusions about the effect of B-fluorination oppose each other (I. Phys. Chem. A 1997, 101, 9410 and J. Mol. Struct.: THEOCHEM 2005, 715, 91). The aim of this study is to resolve this discrepancy and also to evaluate a degree of cyclic pi electron delocalization in all possible polyfluoroborazines. This was done by employing four aromaticity indices, HOMA, NICS, ECRE, and PDI. NICS, ECRE, and PDI gave a satisfactory description of aromaticity of the studied molecules. It was found that N-monofluoroborazine, N-difluoroborazine, and N-trifluoroborazine are the only fluorinated derivatives that exhibit a higher degree of aromaticity compared to borazine. This result opposes the previous ones regarding the influence of N-fluorination.