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

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 C-13 and B-11 chemical shifts support this conclusion.