Polyferrocenylsilane homopolymers and diblock copolymers with pendant ruthenocenyl groups by photocontrolled ring-opening polymerisation

Abstract

The strained, sila[1]ferrocenophane [{Fe(η-C₅H₄)₂}SiMe(η-C₅H₄)Ru(η-C₅H₅)] (4) has been prepared by the reaction of Li[(η-C₅H₄)Ru(η-C₅H₅)] (8) with [{Fe(η-C₅H₄)₂}SiMeCl] (7). Two different routes for the synthesis of 8 were investigated, which differed predominately in the purity of the product obtained. Although the thermal ring-opening polymerisation (ROP) of 4 failed to yield soluble polymeric material, photocontrolled ROP using Na[C₅H₅] as the initiator afforded relatively monodisperse, soluble polymers of predetermined molecular weights and the general formula [(η-C₅H₄)Fe(η-C₅H₄)SiMe{(η-C₅H₄)Ru(η-C₅H₅)}]_n (19). This material was stable to both oxygen and moisture. Electrochemical characterisation of 4 revealed unusual, concentration dependent behaviour as a consequence of the oxidation of the ruthenocenyl groups. This phenomenon was not observed upon oxidation of the Ru centres in 19, presumably due to the sterically encumbered structure of the polymer. The photocontrolled ROP protocol was extended to afford the block copolymers polystyrene (PS)_n-b-[(η-C₅H₄)Fe(η-C₅H₄)SiMe{(η-C₅H₄)Ru(η-C₅H₅)}]_m (22) by the application of a PS-based macroinitiator. These materials represent rare examples of complex polymer architectures where two different metals are incorporated in the same block.