Dehalogenation of vicinal dihalides

Why, among different metals, only zinc is favourable for the dehalogenation of vicinal dihalides?




Zinc is used effectively in the dehalogention of vicinal dihalides because a carbon zinc complex is formed in the mechanism which is probably more stable. This reaction is also known as [Simmon' Smith](https://en.wikipedia.org/wiki/Simmons%E2%80%93Smith_reaction) reaction.


[![enter image description here](https://i.stack.imgur.com/m8AIs.png)](https://i.stack.imgur.com/m8AIs.png)



> 
> The stability and usefulness of the Simmons-Smith reagent (zinc metal)
> may be attributed in part to the **higher covalency of the carbon-zinc
> bond together with solvation and internal coordination of the zinc** (which makes the zinc complex stable). ([Source](http://chem.libretexts.org/Core/Organic_Chemistry/Alkyl_Halides/Reactivity_of_Alkyl_Halides/Alkyl_Halide_Reactions/Reactions_of_Dihalides))
> 
> 
> Reduction of vicinal dihalides by zinc metal proceeds by way of
> oxidative insertion of Zn(0) into a C-X bond, producing an organozinc
> species (stable) which undergoes dehalogenation:
> 
> 
> [![enter image description here](https://i.stack.imgur.com/KyPoP.png)](https://i.stack.imgur.com/KyPoP.png)
> 
> 
> ([source](http://tminehan.com/spring333pdfs/Lecture13org.pdf))
> 
> 
> 


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