The structural chemistry of germanium

The major differences between these elements may be summarized (i) the much greater stability of Ge(ii) than Si(ii), (ii) the greater tendency of Ge(iv) to form 6 bonds, and (iii) the formation of salts by Ge(iv). We deal briefly with these three points. 

The crystal structure of GeF2 (a) projection along the chains, (b) environment of Ge. 

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Coordination Number. Most common coordination numbers for tetravalent compounds are (with typical geometries in parentheses) 4 (tetrahedral), 5 (trigonal bipyramidal), and 6 (octahedral). No examples of coordination numbers higher than 6 have been characterised (cf. tin). Tetrahedral coordination predominates, and hence the structural chemistry of germanium resembles that of silicon rather than tin. 

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