ADDITION OF METHYL GRIGNARD-REAGENTS TO GERMASILENES AND DIGERMENES -UNUSUAL LIGAND-EXCHANGE REACTION OF THE RESULTING GERMYL GRIGNARD-REAGENTS

Methylmagnesium iodide (or bromide) has been found to add to tetramesi tylgermasilene and tetramesityldigermene. The addition to the germasil ene is regioselective, with the methyl group adding to the silicon end of the silicon-germanium double bond to produce a germylmagnesium iod ide (or bromide) species. The germyl Grignard reagents give the corres ponding germanes upon hydrolysis. At 110 degrees C in the presence of excess methylmagnesium halide, the mesityl substituents on the germyl Grignard reagent germanium atom were exchanged for methyl groups. A me chanism involving the a-elimination of MesMgX followed by the addition of MeMgX to the intermediate germylene has been proposed to explain t he observed ligand exchange. Evidence for the presence of intermediate germylenes has been obtained in trapping experiments with 2,3-dimethy lbutadiene.