Germanium tetraaryls

The Wurtz reaction as a method of alkylating germanium tetrachloride has never achieved the popularity of the Grignard reaction, chiefly because the difficulty of control makes it reasonably successful only as a means of preparing the fully substituted tetraalkyls or tetraaryls. The partially substituted germanium halides appear only in low yields since the reaction as usually conducted goes to complete substitution. One explanation is based upon the heterogeneity of the system. The sodium is unavoidably... 

Tetraalkyl and tetraaryl germanium compounds possess monomeric structures with tetrahedrally sited germanium. They are thermally stable and tend to be chemically inert halogenation requires a catalyst (equations 18.49 and 18.50). Chlorides can be obtained from the corresponding bromides or iodides by halogen exchange (equation 18.51). The presence of halo-substituents increases reactivity (e.g. equation 18.52) and makes the halo-derivatives synthetically more useful than R4Ge compounds. 

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