Of polygermanes

The method for preparation of polygermanes by reduction of organodichlorogermanes with alkali metals was replaced by electroreduction of organodichlorogermanes and silanes on magnesium cathodes214. The conditions were mild and safe and the product had a satisfactorily defined weight distribution. Ge—Ge and Ge—Si bonds are successfully created. The following test reactions have been performed to show that conditions are indeed favorable for metal-metal bond formation ... 

TABLE 27. Oxidation of polygermanes and reduction of the oxidized form215... 

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. 

The testing of germanium halide derivatives of other bulky substituents such as Bu did not afford (GeBu% species. Instead, a variety of polygermane species with interesting structures were isolated [38]. The use of the more bulky -CMeEt2... 

TABLE 2. Representative examples for the preparation of polygermanes using different methods... 

In solution, the UV absorption characteristics of polygermanes may be different from those in the solid state. Poly(dihexyl)germane in solution has a kmax value of 327 nm, whereas the same polymer fraction deposited as a thin film on a quartz plate exhibits two... 

Currently, there is growing interest in polymers the frameworks of which are constructed from the Group 14 elements silicon, germanium and tin. Several reviews on polysilanes have appeared in the literature . In the first section of this article we focus on recent developments in the chemistry of polygermanes and polystannanes. The chemistry and structure-property relationship of oligostannanes and low molecular weight polystannanes was the subject of earlier reviews . ... 

Variable-temperature Raman spectroscopy has been used to explore the structure of polygermanes." Ultraviolet photoelectron spectroscopy has been employed to characterize the Ge-Ge backbone bonding." " Additional, Ge NMR spectra have been taken of key precursors for dehydrogenative polymerization, ArGeH3, Ar2GeH2, and Ar3GeH." ... 

Optical tuning of polygermanes and mixed polysi-lane/polygermane systems have been discnssed. Nonlinear optical effects are of particnlar interest. Third-order nonlinear snsceptibUities (/ ) for thin films of ohgo- and polygermanes have been measured.A value of 86 x 10 esu was obtained for copoly(methyl-phenylsilylene/methylphenylgermylene) ... 

---