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.
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Stezowski et al. (1985) studied this question.