Wurtz-type reductive coupling

Polysilylenes are usually prepared by the Wurtz-type reductive coupling of dichlorosilanes with alkali metals. 

Marton, D., Tari, M. Wurtz-type reductive coupling reaction of primary alkyl iodides and haloorganotins in cosolvent/H20(NH4CI)/Zn media as a route to mixed alkylstannanes and hexaalkyidistannanes. J. Organomet. Chem. 2000, 612, 78-84. 

Jones et al. prepared poly(methylphenylsilylene) (p(MPSi)) using a Wurtz-type reductive coupling reaction, followed by reaction with (4-chloromethyl-phenylethyl) dimethylchlorosilylene to produce the a,co-difunctional ATRP initiator [240]. H NMR characterization indicated the presence of several different types of chains ends however, the majority of them appeared to contain the... 

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. ... 

Jones RD, Holder SJ (2006) High-yield controlled syntheses of poly silanes by the Wurtz-type reductive coupling reaction. Polym Int 55(7) 711-718... 

These features have motivated considerable research on the improvement of the Wurtz-type reductive coupling by tuning the reaction conditions, especially by variation of temperature and solvents [20-23]. 

Table 1 Examples of final yields and molecular weight parameters of the isolated polysilanes obtained from the Wurtz-type reductive couplings of dichlorodi-n-hexylsilane (DCDHS), dichloro-n-hexylmethylsilane (DCHMS), dichloromethyl-n-propylsilane (DCMPrS), dichloromethyl-n-octylsilane (DCMOS) and dichloromethylphenylsilane (DCMPS) in THF at 22°C published by Holder and Jones [19]...

A proposed mechanism for the Wurtz-type reductive coupling reaction is depicted in Fig. 5. After initiation via a silyl anion radical to a silyl radical, a four stage propagation step occurs to form the polymeric species. ... 

As the reaction conditions for the preparation of the masked disilenes are as harsh as those of the Wurtz-type reductive coupling reaction, the introduction of functional groups is not trivial. An elegant way to introduce at least some diversity is via the transformation of amine-functionalized polysilanes [39] to the chloro substituted derivatives. These can be converted to alkyl and aryl groups using the corresponding Grignard compounds (Fig. 9) [35]. 

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