Germanium halides tertiary

Reactions between germanium tetrachloride, alkyltrichlorogermane, or dialkyldichlorogermane and secondary amines in petroleum ether yield compounds of the type Ge(NR2)4, RGe(NR2)3, and R2Ge(NR2)2i respectively 4,26). With tertiary amines the germanium halides either do not react or form adducts (cf. Table I). 

The crux of organic mechanistic stereochemistry may be the Walden inversion, the inversion of stereochemistry about a four-coordinate carbon atom by nucleophilic attack of, for example, a hydroxide ion on an alkyl halide. Many reactions of inorganic molecules follow the same mechanism. In contrast, the dissociative mechanism of tertiary halides to form tertiary carbocatanion intermediates is essentially unknown among the nonmetallic elements silicon, germanium, phosphorus, etc. The reason for this is the generally lower stability of species with coordination numbers of less than 4, together with an increased stability of five-coordinate intermediates. This difference is attributable to the presence of d orbitals in the heavier elements (Chapter 18). 

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