Ferrocene-Containing Polycarbosilazanes via the Alkaline-Earth-Catalyzed Dehydrocoupling of Silanes and Amines

We report the use of the alkaline-earth (Ae) metal-catalyzed dehydrocoupling of silanes and amines for the synthesis of ferrocene-containing polycarbosilazanes. The barium complex [Ba(N(SiMe3)2)2·(THF)2] catalyzed the dehydrocoupling of the hydrosilane FeCp(CpSiPhH2) (1) with 1,4-(H2NCH2)2C6H4 under mild conditions to give a polycarbosilazane with pendant ferrocene groups. The polymer could be readily cross-linked by the addition of phenylsilane to the unquenched reaction mixture. Well-defined polycarbosilazanes with ferrocene in the main chain were also obtained from the dehydrocoupling of hydrosilanes Fe(Cp(SiPhH2))2 (3) and Fe(Cp(SiMe2H))2 (IX) with 1,4-(H(Me)NCH2)2C6H4 and 1,4-(H2NCH2)2C6H4, respectively. Crystalline monomeric analogues, FeCp(Cp(SiPh(NHBn)2)) (2, Bn = CH2(C6H5)), and Fe(Cp(SiPh(NHBn)2))2 (4), were also obtained via the dehydrocoupling benzylamine with 1 and 3, respectively. The barium-catalyzed dehydrocoupling of diaminoferrocene with Ph2SiH2 or Ph(Rc)SiH2 (6, Rc = (C5H4)Ru(C5H5)) did not result in polymer, but instead in the formation of the silazane-bridged ansa-[3]ferrocenophanes (Fe(η-C5H4NH)2SiPh2) (5) and (Fe(η-C5H4NH)2SiPh(Rc)) (7), respectively. Both polymeric and molecular products were electrochemically investigated, and the polymers proved to be promising precursors to magnetic iron-containing ceramics in yields of up to 64%.