Synthesis and Properties of the First [4.4]Ferrocenophane-1,3,15,17-tetrayne

Building butadiyne bridges: The kinetically stabilized 1,1′-diethynylferrocene, readily prepared from the pentafulvenoid allene 1, can be transformed into the [4.4]ferrocenophane 2 by oxidative coupling. This compound exhibits a remarkably symmetrical structure in which the electrons are delocalized through the butadiyne bridges; in the crystalline state 2 exists in a helical-chiral conformation.