New quadricyclane-based cyclic polycarbosilanes

Abstract

49 Previously, we showed that silicon-substituted norbornenes and norbornadienes can be widely used for synthesizing macromolecular structures with regularly changed substituents with the aim of revealing theoretically and practically important structure– property relationships [1]. It turned out that polynorbornenes containing trimethylsilyl side groups have good gas transport properties and can serve as efficient membrane materials [2]. We showed that it is precisely Me 3 Si substituents that are responsible for the gas-separation properties and an increase in their number in the monomeric unit enhances the permeability coefficients of polymers. When studying the synthesis of polycarbosilanes of this type, we demonstrated that norbornene and norbornadiene with two SiMe 3 substituents, being active monomers in metathesis polymerization, are almost not polymerized by the addition (vinyl) scheme (Scheme 1). An analogous problem for fluoro-substituted norbornenes was described in [3]. Scheme 1. In the present paper, we describe a new efficient approach to the synthesis of Me 3 Si-substituted norbornenes capable of polymerizing not only by the metathesis mechanism but also by the addition one. This approach involves removal of bulky Me 3 Si substituents from the double bond responsible for polymerization due to the synthesis of 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0 2,5 ]non-7-ene. This compound was synthesized by a reaction that had not been described in organosilicon chemistry, namely, by the reaction of quadricyclane with the corresponding organochlorosilane, trans -1,2-bis(trichlorosilyl)ethylene, and subsequent methylation of the resulting chlorosilyltricyclononene (Scheme 2). Me3Si SiMe3