Synthesis of Polygermanes

Polygermanes have been prepared by the Wurtz-type coupling reaction of diorganogermaniumdichlorides, R2GeCl2 [11-13]. The latter are most readily synthesized by an equilibration between R4Ge and GeCU [12] (see Eq. 8.1). 

The Wurtz-type coupling reaction of R2GeCl2 with sodium in high-boiling solvents such as toluene at reflux temperatures affords polygermanes (see Eq. 8.2). 

High-molecular-weight germanium-silicon copolymers have been prepared by the sodium assisted cocondensation of R2GeCl2 and R2SiCl2 [11] (see Eq. 8.3). 

In order to synthesize poly(arylmethylgermane)s the suitable starting materials would be of the type ArGeMc2H. These compoxmds are prepared by a dearylation reaction of Ar2GeMe2 followed by reduction with lithium aluminum hydride [15] (see Eq. 8.5). 

Demethanation of ArGeMe2H also proceeds in a facile manner to afford high molecular weight polymers H[MeArGe] H M = 5 x 10 - 1 x 10 MJM = 1.3) [15] (see Eq. 8.6). 

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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. 

Germylmetallic compounds derived from transition metals are known 157), but have not yet found applications for the synthesis of polygermanes. 

Okano M, Takeda K, Toriumi T, Hamano H (1998) Electrochemical synthesis of polygermanes. Electrochim Acta 44(4) 659-666... 

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. 

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... 

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