Thermal and transition-metal-catalyzed ring-opening polymerization (ROP) of [1]silaferrocenophanes with chlorine substituents at silicon: A route to tunable poly(ferrocenylsilanes)

The silicon-bridged [1]ferrocenophanes Fe(eta-C5H4)(2)SiRR' [3 (R = Me, R' = Cl), 4 (R = R' = Cl)] with chlorine substituent(s) at silicon were prepared via the reaction of Fe(eta-C5H4Li)(2) . TMEDA (TMEDA = tetramethylethylenediamine) with the chlorinated silanes MeSiCl(3) and SiCl4, respectively. An X-ray diffraction study of indicated that the cyclopentadienyl rings in this species are tilted by an angle of 19.2(4)degrees, typical of other structurally characterized silicon-bridged [1]ferrocenophanes. Thermal ring-opening polymerization (ROP) of 3 and 4 at 250 degrees C yielded the first high molecular weight poly(ferrocenylsilanes) with halogen substituents at-silicon, [Fe(eta-C5H4)(2)SiRR'](n) [7 (R = Me, R' = Cl), 8 (R = R' = Cl)]. Transition-metal-catalyzed polymerization of 3 and 4 with Pd and Pt catalysts also yielded polymers 7 and 8 in solution at room temperature. Polymer 7 was soluble in polar organic solvents and was characterized by H-1, Si-29, and C-13 NMR and elemental analysis. In contrast, poly(ferrocenylsilane) 8 was found to be insoluble in organic solvents and this material was characterized by elemental analysis and derivatization. Substitution of the chlorine side groups in polymer 7 was achieved under mild conditions via reaction with the organolithium reagents MeLi, PhLi, and LiC=C(CH2)(4)H to afford the known polymers [Fe(eta C5H4)(2)SiMe(2)](n) (2a) and [Fe(eta-C5H4)(2)SiMePh](n) (2d) and the new polymer [Fe(eta-C5H4)(2)SiMeC=C(CH2)(4)H](n) (9), respectively. The molecular weights for the completely halogen-substituted poly(ferrocenylsilanes) 2a, 2d, and 9 were estimated by gel permeation chromatography in THF to be in the range of M(w) = 7.4 x 10(4) to 1.7 x 10(5) and M(n) = 3.6 x 10(4) to 1.1 x 10(5) versus polystyrene standards. Substitution of the chlorine atoms in 8 was also demonstrated by reaction of the polymer with MeLi to give 2a.