The development of ferrocene-containing polymers is a highly active field of research which originates from the quest for novel materials showing useful electronic and optical properties. Polymers featuring ferrocene as an integral part of the main chain are particularly interesting, but their synthesis proves to be a major challenge. Our group has recently developed a condensation polymerization approach to borylene-bridged poly(ferrocenylenes) [-fcB(Br)-]_n starting from fc(BBr₂)₂ and HSiEt₃ [fc = (C₅H₄)₂Fe]. The reaction proceeds with liberation of B₂H₆ and gives polymers with up to 40 repeat units. The bromo derivative can be transformed into the corresponding mesityl polymer or the 2,2'-bipyridylboronium salt. The mesityl polymer [-fcB(Mes)-]_n is interesting because it features three-coordinate boron atoms which, due to their empty p-orbital, are well-suited for the promotion of electron delocalization along the polymer chain. The 2,2'-bipyridylboronium salt [-fcB(bipy)-]_nⁿ⁺ possesses four-coordinate boron bridges which are reminiscent of the organic electron acceptor Diquat. As a consequence, charge-transfer interactions between the ferrocene donor fragments and the bipyridylboronium moieties are observed leading to a very deep purple color of the material.

This lecture deals with the synthesis and purification of [-fcB(Mes)-]_n and [-fcB(bipy)-]_nⁿ⁺ and with an investigation of their physical properties ((spectro)electrochemistry, femtosecond laser spectroscopy).