Synthesis and characterization of water-soluble cationic and anionic polyferrocenylsilane polyelectrolytes

Convenient routes to a range of water-soluble polyferrocenylsilane polyelectrolytes are reported. Direct reaction of the protected aminopropynyl reagent LiC=CCH2N(SiMe2CH2)(2) (8) with the substitutionally labile ring-opened polymer [fcSiMeCl](n) (3) (fc = Fe(eta-C5H4)(2)), which is generated via Pt-catalyzed ring-opening polymerization of the silicon-bridged [1]ferrocenophane fcSiMeCl (6), afforded the polymer [fcSiMe{C=CCH2N(SiMe2CH2)(2)}](n) (10). Polymer 10 was also obtained via ring-opening. polymerization of the [Ilferrocenophane fcSiMe{C=CCH2N(SiMe2CH2)(2)} (9) prepared from the reaction of the lithium salt 8 and the substitutionally labile [1]ferrocenophane. 6, which is readily accessible via the reaction of fcLi(2).TMEDA with MeSiCl3. Deprotection. of 10 was readily achieved using THF/MeOH to yield [fcSiMe(C=CCH2NH2)](n) (11), which was conveniently reduced with hydrazine to the analogous aminopropyl polymer [fcSiMe(CH(2)CH(2)CH(2)NH(2)A. (12). Treatment of polyferrocenylsilanes 11 and 12 with HCl generated the water-soluble cationic polyelectrolytes [fcSiMe(C=CCH2NH3Cl)](n) (13) and NcSiMe(CH2CH2CH2NH3Cl)](n) (14), respectively. Cationic polyferrocenylsilanes 13 and 14 were obtained in three steps from polymer 3 with an overall yield of 40-50%. An unexpected rearrangement process took place during the lithiation of the protected aminopropyl bromide Br(CH2)(3)N(SiMe2CH2)(2) (15) and a reaction of the resulting lithium salt with 6 yielded the novel [1]ferrocenophane fcSiMe{N(CH2)(3)SiMe2(CH2)(2)SiMe2} (17) with a rearranged, and ring-expanded, cyclic silylamino substituent. Species 17 underwent thermal ring-opening polymerization to afford [fcSiMe{(CH2)(3)SiMe2(CH2)(2)SiMe2}](n) (18). Treatment of polymer 10 with 1,3-propane sultone afforded the anionic polyelectrolyte [fcSiMe{C=CCH2N(CH2CH2CH2SO3Na)(2)}](n) (19). Polymer 19 was readily reduced with hydrazine to give [fcSiMet{CH2CH2CH2NH(CH2CH2CH2SO3)(CH2CH2CH2SO3Na)}](n) (20) bearing saturated side chains; subsequent deprotonation. yielded the anionic polyelectrolyte [fcSiMe{CH2CH2CH2N(CH2CH2CH2SO3Na)(2)}](n) (21). All three anionic polyelectrolytes 19-21 were obtained in 2-3 steps from 3 with 60-75% overall yields. The polyferrocenylsilane polyelectrolytes 13, 14, and 19-21 were readily soluble in water, making them potentially useful materials for a range of applications.