Studies in the fluorine chemistry of tellurium.

Sulphur chloride pentafluoride and sulphur bromide pentafluoride are the only previously known halide pentafluorides of group VIb. Only two other chloride pentafluorides, of tungsten and rhenium, are known, both prepared by mild direct fluorination of the respective chlorides. The similar preparations of tellurium bromide pentafluoride and tellurium chloride pentafluoride are now described. They are less thermally stable than the sulphur analogues and apparently more reactive to olefines. Evidence has not been found for the formation of tellurium-carbon bonds, but rather of tellurium tetrafluoride from such reactions. Dialkylamino-tellurium pentafluorides have been prepared by cleavage of silicon-nitrogen bonds with tellurium hexafluoride, being the first examples of direct substitution into the hexafluorides of the sulphur subgroup. The only stable disubstituted derivative prepared was cis bis-dimethylamino tellurium (VI) tetrafluoride, though an unstable dimethylamino-diethylamino telluriuin (VI) tetrafluoride was obtained. No evidence was found for the existence of further substitution products. The tellurium nitrogen bond in the dialkylaminotellurium pentafluorides is not readily cleaved by anhydrous acids or hexafluoroacetone. The 19F and 1H nmr spectra of the new compounds are described and discussed. Attempts to directly locate the 125Te resonance are described, while a sample of dimethylaminotellurium pentafluoride has been given to Dr. W. McFarlane (Sir John Cass College) for examination by heteronuclear magnetic resonance techniques. The thesis concludes with a review of tellurium (IV) fluorine chemistry and a description of some preliminary reactions of tellurium tetrafluoride with simple nitrogen containing compounds. A new adduct of tellurium tetrafluoride and sulphur trioxide is also described.