Living Anionic Polymerization of Phosphorus-Bridged [1]Ferrocenophanes:  Synthesis and Characterization of Well-Defined Poly(ferrocenylphosphine) Homopolymers and Block Copolymers

The living anionic ring-opening polymerization (ROP) of the phosphorus-bridged [1]ferrocenophane (η-C5H4)2FePPh initiated by n-BuLi in THF at 25 °C has allowed the preparation of well-defined poly(ferrocenylphenylphosphines) [(η-C5H4)2FePPh] n 5, with molecular weight control, narrow polydispersities, and controlled end-group structures. Reaction of polymers 5 with sulfur allowed the synthesis of the analogous poly(ferrocenylphenylphosphine sulfides) [(η-C5H4)2FeP(S)Ph] n 6. Analysis of the high-molecular-weight polymers 5 and 6 (where n = 100) by DSC showed glass-transition temperatures of 126 and 206 °C, respectively. The absence of melt transitions and the featureless WAXS profiles indicated that the materials are amorphous. The living nature of the ROP also permitted the synthesis of well-defined block copolymers, poly(ferrocenylphenylphosphine)-b-poly(dimethylsiloxane) (PFP-b-PDMS), PFP11-b-PDMS81 (7a) and PFP50-b-PDMS141 (7b), and poly(ferrocenylphenylphosphine)-b-poly(ferrocenyldimethylsilane) PFP11-b-PFS11 (8). Analysis of the block copolymer 7b by DSC showed the presence of individual thermal transitions for each block which indicated that they were incompatible. Metal coordination studies on copolymer 7b showed that this material coordinates PdCl2, to yield the insoluble copolymer 11, as well as Fe(CO)4, which resulted in the formation of 12 which remained soluble in hexane.