Evidence for “Halogen-Dance” and Ring-Exchange Reactions in Chloro-methylthio-ferrocenes

Abstract

The pentachloroferrocenes [C5Cl5]Fe[C5H4X] (X = H, Br, SMe) react with LiTMP and MeSSMe to form mixtures of compounds, that contain besides the expected products of deprotonation also one or more complexes with a [C5Cl4(SMe)] ligand. This latter observation makes the otherwise rarely observed occurrence of “halogen dance reactions” in chloroaromatics very probable. 1,2,3-Trichloroferrocene yields with BuLi and MeSSMe products of both halogen-metal-exchange and of deprotonation. Additionally, in all examined systems, the observation of some highly-substituted complexes with eight or more substituents hints to the involvement of cyclopentadienyl exchange reactions, which has also rarely been observed under such mild conditions. The molecular structures of [C5Cl4(SMe)]Fe[C5H3BrX] (X = SMe or SOMe), [C5Cl4(SMe)]Fe[C5H2Cl(SMe)2], [C5Cl2(SMe)3]2Fe, and [C5HCl3(SMe)]2Fe have been determined by X-ray diffraction.