The molecular structure of substituted cyclopentadienyl cations

Abstract

Internal or external substitution of the cyclopentadienyl cation brings about hetero- or carbocyclic compounds that differ greatly in their electronic and molecular structure. Depending on the substitution pattern and the nature of the heteroatoms the compounds constitute two series. Each series is related to one of the two Jahn—Teller distorted structures of the parent cyclopentadienyl cation. This classification follows from qualitative molecular orbital interaction schemes which are fully consistent with correlation diagrams obtained by molecular orbital analysis. Semiempirical MINDO/3, MNDO and STO-2G ab initio calculations of the molecular geometry of nitrogen and boron substituted cyclopentadienyl cations furnished evidence in favour of their classification into two series of distorted structures.