CH3MgI in diethyl ether; benzene Norbornadiene-compound and PhCH2I are heated at 75°C in benzene under Ar, benzylic products (10-20 percent) are methylated in Et2O (MeMgI, stirring at 0°C for 0.5 h, then stirring at room temp. for 1 h).; addn. of H2O and NH4Cl, sepn. of organic and aq. phases, extn. of aq. phase (Et2O), removal of solvent, investigation by GC-MS anal., further products are Me8Ge3, Me10Ge4, Me12Ge5 in ca. 70 percent yield;