Polygermanes synthesis

Soluble and weU-characterized polygermane homopolymers, (R Ge), and their copolymers with polysdanes have been prepared by the alkaH metal coupling of diorgano-substituted dihalogermanes (137—139), via electrochemical methods (140), and by transition-metal catalyzed routes (105), as with the synthesis of polysdanes. 

Since the field was last reviewed,1 a number of linear and cyclic oligogermanes have been reported, as have a number of new methods for the synthesis of polygermanes. The Ge-Ge single bond length is typically considered to be approximately 2.45 A, which is twice the atomic radius of germanium. 

Berry and co-workers have reported a new method for the synthesis of moderate to high molecular weight polygermanes in very high yields by the catalytic coupling of tertiary germanes.83 This ruthenium-catalyzed process appears to be the first example of a catalytic demethanative coupling, in which element-element bonds are produced with the concurrent elimination of CH4 [Eq. (58)]. 

SCHEME 3. Electrochemical synthesis of a three-dimensional polysilane-polygermane copolymer 5... 

Non-symmetrical organohydropolygermanes are usually difficult to obtain. In some cases, the reaction of a germylanion with an organohalohydrogermane allows their synthesis (Scheme 25, a), but when the organohalohydrogermane is too acidic , a competitive lithiation reaction (Scheme 25, b) gives polygermanes through a-elimination . 

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