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Transition Metal Catalyzed Ring-Opening Polymerization (ROP) of Silicon-Bridged [1]Ferrocenophanes: Facile Molecular Weight Control and the Remarkably Convenient Synthesis of Poly(ferrocenes) with Regioregular, Comb, Star, and Block Architectures

1998; American Chemical Society; Volume: 120; Issue: 33 Linguagem: Inglês

10.1021/ja981429h

1943-2984

Paloma Gómez‐Elipe, Rui Resendes, Peter M. Macdonald, Ian Manners,

Silicone and Siloxane Chemistry

Transition metal (PtII or Pt0) catalyzed ring-opening polymerization (ROP) of silicon-bridged [1]ferrocenophanes has been found to permit simple and convenient control of the regiostructure, molecular weight, and architecture of poly(ferrocenes). Whereas thermal ROP of the unsymmetrical silicon-bridged [1]ferrocenophane Fe(η-C5H4)(η-C5Me4)SiMe2 (3) at 150 °C proceeds via a nonselective cleavage of the Si−CpH and Si−CpMe bonds (CpH = η-C5H4, CpMe = η-C5Me4) to yield an amorphous, regioirregular poly(ferrocenylsilane), the Pt-catalyzed ROP of 3 in solution at 25 °C involves selective cleavage of the Si−CpH bond to afford a crystalline poly(ferrocenylsilane) 5 with a regioregular microstructure. Regioselective ROP of 3 was also detected during the Pt-catalyzed copolymerization of 3 with benzosilacyclobutane (7). The presence of Et3SiH during the Pt-catalyzed ROP of the [1]silaferrocenophane Fe(η-C5H4)2SiMe2 (1) permits molecular weight control and the formation of poly(ferrocenylsilanes) capped by Et3Si and Si−H groups, Et3Si−[Fe(η-C5H4)2SiMe2]n−H (11) with Mn = 2000−45 000 and PDIs of 1.1−2.3. The use of siloxane-based materials with Si−H groups such as the random copolymer [MeHSiO-/-Me2SiO]n or the cyclotetrasiloxane [MeHSiO]4 in place of Et3SiH allowed the preparation of comb-shaped polysiloxane-poly(ferrocenylsilane) graft copolymers (12) and star-shaped polymers (16) with a cyclic siloxane core, respectively. In addition, the use of Si−H terminated poly(dimethylsiloxane)s in place of Et3SiH provided facile access to poly(ferrocene)-poly(siloxane)-poly(ferrocene) triblock copolymers (18).