Digermanes reactions

Bulky substituents confer stability on organogermanium compounds. Scheme 1 shows possible derivatization reactions for some substitued germanes and digermanes. Compounds d and e are obtained from reactions a and b3 as mixtures of diasteroisomers, however, reactions a3, b4 and b3 are more stereospecific. Compounds b-i in the scheme were characterized by H NMR spectra118. 

SCHEME 1. Derivatization reactions for germanes and digermanes stabilized by bulky substituent... 

Digermane hydrides are obtained by the following methods215. Reaction of R2GeH2 (where R = Ph or mesityl), with Me3CLi, produces R2GeHLi with 80 to 95% yields ... 

The unstable di- or triiodogermane can be converted into the bromide or chloride after reaction with the corresponding silver halides273. Silver halides can also be used for the preparation of digermane monohalides275 ... 

Reaction of GeBr4 with f-butyllithium gave a mixture of dibromo-di-t-butyl germane and l,l,2,2-tetrabromo-l,2-di-f-butyl-digermane, 114. 

The reaction of trimethylgermyllithium with silicon tetrachloride, because of steric hindrance, gave a low yield of tetra(trimethylgermyl)silane, and hexamethyldigermane was obtained as the major product. The digermane resulted from a lithium/halogen exchange reaction (equation 123)32. 

The activation energy of the pyrolysis of digermane has been interpreted to be the Ge-Ge bond dissociation energy 52 This makes Z)(H3Ge GeH3) =34 kcal. The reaction is 1st order over the middle period, has an induction period, and is retarded towards the end. It is almost certainly a chain process, and there appears to be little justification for this interpretation of the activation energy. 

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