Demethanative coupling

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)]. 

The demethanative coupling appears to be a step polymerization, as initial consumption of the germane monomer produces oligogermanes within the first few minutes, followed by further condensation to high polymer within hours at 25°C. Molecular weights of the permethylpolyger-mane (GPC, polystyrene calibration) range from Mn 1-4 X 104 and... 

The authors proposed a mechanism for the demethanative coupling where Ge-C bond cleavage and Ge-Ge bond formation are attained by sequential a-CH3 and germyl to germylene migration steps via an intermediacy of metal-germylene species. 62b... 

SCHEME 6. Ruthenium-catalyzed demethanative coupling of trimethylgermane... 

Katz, S.M., J.A. Reichl, and D.H. Berry. 1998. Catalytic synthesis of poly(arylmethylgermanes) by demethanative coupling A mild route to sigma-conjugated polymers. J Am Chem Soc 38 9844. 

All values were measured in THP unless otherwise noted. Synthesized via demethanative coupling (46). Synthesized via electrochemical polymerization (47). Synthesized via catalytic polymerization (48). 

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