Ab initio MO and DFT study of syn-sesquinorbornatrienyl dication and its isoelectronic boron analogue

Abstract

The structure of dication 3, derived by replacement of the CH₂ bridges in syn-sesquinorbornatriene (5) by the ⁺CH groups and its isoelectronic boron analogue 4 were investigated using ab initio MP2/6-31G* and density functional B3LYP/6-31G* methods. Three energy minima were found in both species, all of them exhibiting strong bis-homoaromatic interaction of the electron deficient bridges with either central or peripheral double bond(s). The calculated ¹³C and ¹¹B chemical shifts support this conclusion.