Mössbauer and T.G.A studies of some hexahalotellurate(IV) salts

Abstract The reaction of tellurium(IV) oxide with concentrated hydrochloric acid gives a solution from which (Ph 4 As) 2 TeCl 6 may be precipitated. This material has 125 Te Mossbauer parameters which suggest that the anion may be distorted towards, C 3v symmetry. By contrast the hexabromotellurate and the hexachlorotellurate formed when a benzene solution of TeCl 4 is treated with Ph 4 AsCl are ‘normal’. TGA studies show that the ammonium and tetramethyl ammonium hexachloro- and hexabromotellurates decompose more or less cleanly to tellurium tetrahalide ad ammonium halide. The decomposition of the tetraphynlarsonium salts is more complex.