Redistribution Reactions between Tetraalkyl or Tetraarylgermanes, and Germanium Tetrahalides

Redistribution Reactions between Tetraalkyl or Tetraarylgermanes, and Germanium Tetrahalides 

These redistribution reactions are possible at atmospheric pressure under the action of MW. Irradiation is performed for a few minutes in the presence of the same catalyst [57]. These reactions with the less volatile germanium tetrabromide (54b) (b.p. 184 °C) have also been performed by use of the GS-MW process, without added catalyst (Table 9.3, entries 1 and 3) [15]. In this instance, despite the use of weaker incident power, the temperature reached 420 °C, very much higher than that obtained under the action of MW irradiation of a reaction mixture containing AlBr3 (200 to 250 °C) (Table 9.3, entries 2 and 4) The presence of this catalyst substantially favors redistribution towards the dibrominated products (56b) (84% for R = Bu, 85% for R = Ph) relative to the monobrominated compounds (56a), which are the major products of the GS-MW process (78% and 43% respectively). 

Entry R CeBr4l=l R4CeI=l AIBrjI l Exp. conditions R4CeW 56 (a b c)W YieldM 

The tribrominated product (56c), the most difhcult to prepare, have been obtained with a rather high selectivity (73 to 80%) by use of the catalytic process under the action of MW [57]. In this reaction, therefore, the GS-MW process seems less effective than the MW-assisted and AlXs-catalyzed process. 

Redistribution Reactions between Tetraalkyl- or Tetraarylgermanes and Germanium Tetrahalides 

Entry R Initial mixture (mmol) GeBr4 R4Ge AlBr3 Exp. conditions Products (%) R4Ce 46 (a/b/c) Yieldd 

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