octachlorocyclotetraphosphazatetraene in acetone

in tetrahydrofuran inert-atmosphere, refluxed for 24 h with stirring; THF removed by rotary evaporation, residue dried in vacuum, extracted with hot heptane, filtered, cooled (-55°C) for several days, filtered, rapid extracted with cold acetone or filtered a chloroform soln. through Florosil;