“…The twist of the naphthalene bridges, common to 1,8-bismetallocenylsubstituted naphthalenes, is caused by the repulsion of the two naphthalene-bonded Cp ligands. [11,13,14,15,17,19] The magnitude of the twist correlates roughly with the relative electron density on the naphthalene bonded Cp rings, which is demonstrated by the angle between the best planes of the Cp ligands. It is smallest for the dicationic species 1 and 3, 20.3 and 22.18, respectively, and increases for the neutral compounds 2 and 5.…”