Wurtz-type coupling, synthesis

WurtZ-Type Coupling of Dihalosilanes. Several approaches have been developed for the synthesis of polysdanes. However, the most commonly utilized method is based on the Wurtz-type alkah metal coupling of dichlorosilanes. Both homo- and copolymers can be prepared this way (eq. 10). 

SCHEME 13. Synthesis of polydibutylstannane by the Wurtz-type coupling... 

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],... 

Synthesis of Cyclotetrasilane-Fused Octasilacuneane 487 Wurtz-type coupling of 1,1-di-tert-butyl-1,2-dichloro-2,2-diphenyldisilane with lithium 487... 

Synthesis of Cyclopentasilane-Fused Hexasilabenzvalene 490 Wurtz-type coupling of 2,2-di-tert-butyl-1-chloro-1,1-diphenyldisilane with... 

Wurtz-type coupling of chlorosilanes with alkali metals is an important method of silicon—silicon bond formation. Since the Wurtz-type coupling was reported by Kipping in 1921 (15,16), this method has been used for the synthesis of oligosilanes. 

Similar to the chemistry of cyclotrisilanes also for that of the respective fonr-membered rings initially mainly the Wurtz-type coupling protocol was used as the synthetic approach. For the synthesis of cycloalkyl substituted cyclotetrasilanes Roewer and coworkers were employing this strategy (4) [97]. 

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