Biferrocenes with Heteroaromatic Spacers:  Synthesis, Structure, and Electrochemistry

Diferrocenyl complexes containing thiophene or furan in the conjugation chain have been synthesized by Wittig, McMurray, and Sonogashira coupling reactions. Ferrocene and the heteroaromatic rings are connected by vinyl or ethynyl linkages. These biferrocenes were characterized by elemental analysis, NMR, optical and mass spectroscopy, and cyclic voltammetric studies. The structure of (η⁵-C₅H₅)Fe(η⁵-C₅H₄)CHCHC₄H₂SCHCH(η⁵-C₅H₄)Fe(η⁵-C₅H₅) has been determined by single-crystal X-ray diffraction methods. The interaction between the ferrocene units are weak, and thus in cyclic voltammetry a single two-electron redox process with a larger peak-to-peak separation was observed.