Metal germanium halides

The triphenylmethyl-substituted germanium halide 31 can be prepared in modest yield using GeCl4 and contains a formally seven-coordinate germanium metal center (Scheme 9). The structure of 31 (Figure 2, Table 11) is a tricapped tetrahedral structure where all the three Ge-O distances are shorter than the sum of the van der Waals radii (3.62 A). A series of hypervalent germanium halides 32-34 can be prepared, as shown in Scheme 10.95 The fluoride 32 is hexacoordinate, whereas the chloride 33 and bromide 34 are pentacoordinate. 

Other transition metal anions fail in giving the expected compounds . Germanium halides react more easily but are useless for the preparation of optically active compounds. Indeed, optically active bromo-germanes are not known, and chlorogermanes rapidly racemize in ether or tetrahydrofuran. ... 

Formation of Germanium-Transition and Inner Transition Metal Bond 5.8.4.3. from Germanium Halides... 

All Group IV elements form tetrachlorides, MX4, which are predominantly tetrahedral and covalent. Germanium, tin and lead also form dichlorides, these becoming increasingly ionic in character as the atomic weight of the Group IV element increases and the element becomes more metallic. Carbon and silicon form catenated halides which have properties similar to their tetrahalides. 

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