Reversible,Strain-Controlled Haptotropic Shifts of Cyclopentadienyl Ligands in [1]-and [2] Metallocenophanes

摘要

Strained rings containing transition-metal elements are of growing interest as a result of their intriguing structures,enhanced reactivity,and ability to function as precursors to high-molecular-weight metallopolymers through ring-opening polymerization.Ring-strained metallocenophanes and their analogues have attracted particular attention in this regard and their ring-opened polymeric derivatives exhibit a variety of interesting properties.The appreciable ring tilting(a)of the planes of the Cyclopentadienyl ligands in ferrocenophanes relative to ferrocene,where the ligands are parallel(alpha = 0deg),has been shown to comprise the major contribution to ring strain.