THE SYNTHESIS AND VIBRATIONAL-SPECTRA OF FLUOROSULFATE DERIVATIVES OF TITANIUM, ZIRCONIUM AND HAFNIUM

The syntheses of the binary fluorosulfates, Zr(SO3F), and Hf(SO3F)4, by oxidation of the corresponding metal powders with bis(fluorosulfuryl) peroxide, S2O6F2, in fluorosulfuric acid, HSO3F, are described. The resulting products are white hygroscopic solids which are not sufficiently soluble in HSO3F to allow electrical conductivity and NMR studies or Hammett acidity function (H-0) determinations in order to evaluate their use as Lewis acids in conjugate superacid systems. Oxidation of titanium under similar conditions resulted in the formation of a greenish-yellow resin-like material of limited thermal stability with the approximate composition Ti(SO3F)4. However, infrared spectra indicated the presence of small amounts of HSO3F. In addition, the solvolysis of ZrCl4 in an excess of HSO3F at 25-degrees-C has been investigated as a potential route to Zr(SO3F)4. The results indicate that short reaction times of 1-2 d yielded incompletely substituted products of the approximate composition ZrClx(SO3F)4-x (x = 0.22), while prolonged reaction times of 3-4 weeks gave rise to partially decomposed materials of approximate composition ZrO0.5F1.5(SO3F)1.5. The ability of all three tetrakis(fluorosulfato) metallates to act as SO3F- ion acceptors is evident from the isolation of thermally stable salts of the composition Cs2[M(SO3F)6] (M = Ti, Zr or Hf) when the metal oxidation was carried out in the presence of 2 mol equiv. of CsSO3F. All the materials were characterized by their vibrational spectra, which are extremely similar and closely resemble those of previously reported cesium hexakis(fluorosulfato) metallates.