Cationic homopolymerization of 1,1′‐diisopropenylferrocene

Abstract 1,1′‐Diisopropenylferrocene (1a) was homopolymerized using trifluoroacetic acid or boron trifluoride etherate as initiators, with excellent yields (>90%) of polymer (8100 < M̄n < 14700). Spectroscopic evidence established an initial protonation of 1a to give a tertiary monocarbenium ion (3) which does not readily undergo intramolecular cyclization (into 4). Analysis of isolated homopolymers by 1H and 13C NMR spectroscopy revealed significant residual unsaturation, consistent with facile chain transfer. Adventitious oxidation occurred during workup to give a mixed valence (Fe(II)/Fe(III)) polymer which could be distinguished spectroscopically from the unoxidized polymer.