Wurtz-type coupling, synthesis polysilanes

WurtZ-Type Coupling of Dihalosilanes. Several approaches have been developed for the synthesis of polysilanes. However, the most only utilized method is based on the Wurtz-type alkali metal coupling of dichlorosilanes. Both homo- and copolymers can be prepared this way (eq. 

Synthesis. The polysilanes can be produced from silyl dichlorides by the Wurtz-type coupling (9) ... 

Synthesis of Polysilanes by Wurtz-type Coupling Reactions... 

ABSTRACT. Polysilanes, (-SiRR -)n, represent a class of inorganic polymers that have unusual chemical properties and a number of potential applications. Currently the most practical synthesis is the Wurtz-type coupling of a dihalosilane with an alkali metal, which suffers from a number of limitations that discourage commercial development. A coordination polymerization route to polysilanes based on a transition metal catalyst offers a number of potential advantages. Both late and early metal dehydrogenative coupling catalysts have been reported, but the best to date appear to be based on titanocene and zirconocene derivatives. Our studies with transition metal silicon complexes have uncovered a number of observations that are relevant to this reaction chemistry, and hopefully important with respect to development of better catalysts. We have determined that many early transition metal silyl complexes are active catalysts for polysilane synthesis from monosilanes. A number of structure-reactivity correlations have been established, and reactivity studies have implicated a new metal-mediated polymerization mechanism. This mechanism, based on step growth of the polymer, has been tested in a number of ways. All proposed intermediates have now been observed in model reactions. 

The lack of sufficient control of molecular weight distributions, molecular weight and polymer structure of polysilanes via a Wurtz-type coupling reaction led Sakurai and co-workers to develop an alternative method for polysilane synthesis in 1989 [31],... 

Most recently, a simple, mild, one-pot immobilization method was developed to attach the rigid rod-like helical polysilane, poly( -decyl-/-butylsilylene), via a siloxy linkage to hydrophilic quartz or mica substrate surfaces.28 195 Triethylamine was used as a catalyst to couple the Si-H and/or Si-OR termini of the dialkylpolysilane chains (which are generated during the course of Wurtz-type synthesis and workup)51,195 with the surface -OH groups. AFM, UV, and IR data were used to analyze the reactions. 

The synthesis of polysilanes by the Wurtz-type reductive-coupling reaction is shown in Scheme 11.6. It is applicable to the synthesis of any polysilane, the substituents of which can withstand the harsh reaction conditions. This limits the systems to ones with aUcyl, aryl, silyl, fluoroalkyl, and ferrocenyl substituents but other structures are accessible through post-polymerization chemistry. ... 

Scheme 11.6. Synthesis of polysilanes by the Wurtz-type reductive-coupling reaction.

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