Germylenes acetylenes

The electronic properties of germanium have led to an interest in incorporating the element into extended polymeric chains due to the intrinsic properties of the polymers themselves or in their use as precursors for material synth-esis. Catalytic co-polymerization of the germylene Ge[N(SiMe3)2]2 with various substituted acetylenes leads to... 

Although very little is known for the reactions of isolated germylenes 146, 147, and 148, diarylgermylene (150) was found to undergo a variety of reactions with olefins, dienes, acetylenes, alcohols, isothiocyanates, elemental chalcogens, and hydrosilanes as in the cases of less hindered, transient germylenes previously reported. 

The oxidation-reduction route was also used to prepare copolymers 53 of bis[bis(tri-methylsilyl)amido]germanium and acetylene derivatives130 (Scheme 27). Rhodium compounds such as [Rh(norbornadiene)Cl]2 were used as catalysts. In contrast to other polymers prepared from germylenes, the monomer-to-monomer ratio was not regular. Relatively low molecular weight polymers 53 (Mn = 1 x 103-104) were isolated. 

R = Ph, tt-Bu, tt-Pen, tt-Hex SCHEME 27. Transition metal-catalysed addition-polymerization of germylenes to acetylenes... 

Rates of gas-phase additions of dimethylsilylene, Me2Si, to acetylene and its mono- and dimethyl derivatives showed an approximate ratio of 1 2 4. This behaviour could suggest electrophilic character of the silylene. On the other hand, reactivity of dimethylgermylene, Me2Ge, with acetylenes is high for t-Bu—C=C—CN and thus not favouring electrophilic character of the germylene. ... 

Organogermanium polymers were prepared by Kobayashi and coworkers via the reaction of a germylene (175) with acetylene monomers (176) in the presence of a rhodium catalyst (Scheme 43). Copolymer 177 incorporated a larger ratio of polyacetylene units than germanium units in the backbone. 

---