magnesium in tetrahydrofuran; N,N,N',N',N'',N''-hexamethylphosphoric triamide all manipulations under dry Ar; heating soln. of Me3SiCl containing Mg turnings (90°C), adding dropwise dichlorodimesitylgermane in THF, heating (40 min), cooling, filtering, adding hexane, adding 10percent HCl; washing hexane layers (H2O), concg. (vacuum); recrystn. (hexane/ethanol);

in hexane T=-70°C; 48 h; UV-irradiation;

in hexane T=-70°C; 20 h; UV-irradiation;

in hexane T=-70°C; 20 h; UV-irradiation;

in hexane byproducts: Si2(CH3)6, C6H3(CH3)3, (CH3)3SiC6H2(CH3)3; Irradiation (UV/VIS); (Ar); photolysis of hexanes soln. of germanium compd. and dimethylbutadiene at -70°C for 24 h; evapn., chromy. (silica gel, hexanes) to isolate dimesitylgermacyclopentene deriv., thin layer chromy. (silica gel. hexanes), NMR and MAS;