in gas byproducts: hexabutylditin; placing starting material in a porcelain cup in the sublimation chamber of a flash vac. thermolysis apparatus, react. at 800-850°C in the main oven and 250-300°C in the sublimation oven (10E-2 mm), oven packed with broken porcelain; vapors quenched on a dewar cold finger, pyrolysis tube cooled to room temp., product washed with ether from the dewar surface, ether evapd., chromy. (florisil);