The structure of an aromatic 10π electron ‘dianion’: dilithium pentalenide

Abstract

In agreement with the predictions of MNDO calculations, a crystal structure determination shows that the metal atoms in a dilithium pentalenide–dimethoxyethane complex bridge opposite faces of the 10π aromatic system; this arrangement (5) is favoured because each carbon atom in the delocalized dianion moiety has a lithium neighbour, the lithium cations ‘communicate’ elctrostatically, and dipolar repulsion does not occur.