Improved synthesis of Te6(AsF6)4, and TeF3·AsF6

Original preparation of Te6(AsF6)41 involved the reaction of elemental tellurium with excess AsF5 for several days followed by a tedius and not totally complete separation from Te4(AsF6)2. The present method involves the oxidation of tellurium with AsF5 in the presence of traces of Br2 in SO2 at r.t. (eq. 1). The sparingly soluble Te6(AsF6)4 is easily separated from other side products, TeF4 and TeF3·AsF6 as they are highly soluble in SO2. TeF3·AsF6 was detected by NMR in the solutions of TeF4 and excess AsF5 in SO22. The present preparation of TeF3AsF6 (eq. 2) is effected in a simple one step, without the prior preparation of TeF4, which is prepared by the reaction of TeO2 and SF4 at high pressure3. The method has been extented (eq. 3) to give TeF4 but needs careful removal of traces of TeF3·AsF6. Te + AsF5 TeF4 + 2 AsF3 (3)