in dichloromethane CH2Cl2 added to 2,2-bis(dimethylchlorostannyl)propane, excess of SnCl4 added slowly, agitated for 5 min, concd. (vac.), heated at 60°C overnight; warmed to 60°C for 0.5 h with slow reducing pressure to 0.01 Torr, recrystd. (CCl4); elem. anal.;