Despite its very modest utility, the Wurtz reaction is widely cited as representative of reductive coupling.
[1] The reaction proceeds by an initial metal–halogen exchange, which is described with the following idealized stoichiometry: This step may involve the intermediacy of radical species R·.
The organometallic intermediate (RM) next reacts with the alkyl halide (RX) forming a new carbon–carbon covalent bond.
In the cases of 1,3-, 1,4-, 1,5-, and 1,6- dihalides, Wurtz-reaction conditions lead to formation of cyclic products, although yields are variable.
Hexamethyldisilane arises efficiently by treatment of trimethylsilyl chloride with sodium: Tetraphenyldiphosphine is prepared analogously: Similar couplings have been applied to many main group halides.