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⋮CCH 2 N(SiMe 2 CH 2 ) 2 ( 8 ) with the substitutionally labile ring-opened polymer [fcSiMeCl] n ( 3 ) (fc = Fe(η−C 5 H 4 ) 2 ), which is generated via Pt-catalyzed ring-opening polymerization of the silicon-bridged [1]ferrocenophane fcSiMeCl ( 6 ), afforded the polymer [fcSiMe{C⋮CCH 2 N(SiMe 2 CH 2 ) 2 }] n ( 10 ). Polymer 10 was also obtained via ring-opening polymerization of the [1]ferrocenophane fcSiMe{C⋮CCH 2 N(SiMe 2 CH 2 ) 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 MeSiCl 3 . Deprotection of 10 was readily achieved using THF/MeOH to yield [fcSiMe(C⋮CCH 2 NH 2 )] n ( 11 ), which was conveniently reduced with hydrazine to the analogous aminopropyl polymer [fcSiMe(CH 2 CH 2 CH 2 NH 2 )] n ( 12 ). Treatment of polyferrocenylsilanes 11 and 12 with HCl generated the water-soluble cationic polyelectrolytes [fcSiMe(C⋮CCH 2 NH 3 Cl)] n ( 13 ) and [fcSiMe(CH 2 CH 2 CH 2 NH 3 Cl)] 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(CH 2 ) 3 N(SiMe 2 CH 2 ) 2 ( 15 ) and a reaction of the resulting lithium salt with 6 yielded the novel [1]ferrocenophane fcSiMe{N(CH 2 ) 3 SiMe 2 (CH 2 ) 2 SiMe 2 } ( 17 ) with a rearranged, and ring-expanded, cyclic silylamino substituent. Species 17 underwent thermal ring-opening polymerization to afford [fcSiMe{N(CH 2 ) 3 SiMe 2 (CH 2 ) 2 SiMe 2 }] n ( 18 ). Treatment of polymer 10 with 1,3-propane sultone afforded the anionic polyelectrolyte [fcSiMe{C⋮CCH 2 N(CH 2 CH 2 CH 2 SO 3 Na) 2 }] n ( 19 ). Polymer 19 was readily reduced with hydrazine to give [fcSiMe{CH 2 CH 2 CH 2 NH(CH 2 CH 2 CH 2 SO 3 )(CH 2 CH 2 CH 2 SO 3 Na)}] n ( 20 ) bearing saturated side chains; subsequent deprotonation yielded the anionic polyelectrolyte [fcSiMe{CH 2 CH 2 CH 2 N(CH 2 CH 2 CH 2 SO 3 Na) 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.