CYCLOTRIGERMANES - SYNTHESIS AND THERMAL-DECOMPOSITION

The reactions of dihalogenogermanes R(2)GeX(2) (X = halogen) with Mg a nd MgBr2 in tetrahydrofuran produce the corresponding cyclotrigermanes (R(2)Ge)(3), and cyclotetragermanes (R(2)Ge)(4); the preferred ring s ize of the products depends on the substituents at the germanium atom. In the thermolysis of hexamesitylcyclotrigermane (2), dimesitylgermyl ene (11) and tetramesityldigermene (8) are generated. While 11 can be trapped directly with 2,3-dimethyl-1,3-butadiene to give dimesitylgerm acyclopent-3-ene (9), 8 rearranges to mesityl(trimesityl)germylene (12 ), which leads to the formation of mesityl(trimesitylgermyl)germacyclo pent-3-ene (10). Nevertheless, in the thermolysis of 2 with paraformal dehyde, thiobenzophenone, or phenylacetylene as trapping reagents the expected cyclo-adducts of tetramesityldigermene (8) are formed. Furthe rmore when hexamesitylcyclotrigermane (2) is reacted with acetylene in the presence of catalytic amounts of palladium complexes, a C-unsubst ituted germole 21 is obtained in good yield.