Stable polycyclic anions: dianions from overcrowded ethylenes

Abstract

Stable overcrowded ethylene dianions, viz. bifluoren-9-ylidene dianion (1)2– and bi-(4H-cyclopenta[def]phenanthren-4-ylidene) dianion (2)2– were prepared via metal reduction and characterized by 1H and 13C n.m.r. spectroscopy; the spectroscopic results as well as ωβ calculations performed on the hydrocarbons (1) and (2) and the corresponding dianions (1)2– and (2)2– are discussed with respect to their diatropicity and spatial structure.