syn-Sesquinorbornenyl carbocations and their boron analogues: an ab initio and DFT study

Abstract

MP2 and DFT calculations employing 6-31G* were carried out to investigate the structure of some of the carbocations and their boron analogues embedded in the syn-sesquinorbornene framework, hitherto not observed experimentally. The calculated minimum energy structures of all species provide evidence for homoconjugative interaction between the electron deficient center(s) and the carbon–carbon double bond. The use of isodesmic reactions based upon MP2(fc)/6-31G* energies indicates that the homoconjugative stabilisation of mono- and di-cations is greater than those of the isoelectronic boron compounds. The calculated ¹³C and ¹¹B NMR chemical shifts support this conclusion.