3,3-Diferrocenylcyclopropene

Dehydrohalogenation of isomeric 2-chloro- and 2-bromo-1,1-diferrocenylcyclopropanes (Z- and E-isomers with respect to the ‘bisecting’ ferrocenyl substituent) under the action of ButOK in DMSO afforded 3,3-diferrocenylcyclopropene. In solution, this underwent facile opening of the small ring to give 3-ferrocenyl-1H-cyclopentaferrocene (∼55%) and 1,1-diferrocenylpropene (15%). The spatial structure of Z-2-chloro-1,1-diferrocenylcyclopropane and 1,1-diferrocenylcyclopropane were elucidated by X-ray diffraction analysis of a single crystal.