Hydroxy Methoxy Tellurium Tetrafluoride

The hydroxy methoxy tellurium tetrafluorides are surprisingly stable compounds. No hydrolysis or isomerization occurred in 96% sulfuric acid up to a temperature of 150°. The tran. -compound seems to be thermodynamically more stable than the cw-derivative  

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The reaction of trans-dimethoxy tellurium tetrafluoride with pyridine produced pyridinium /ra .v-(methoxy)oxo(tetrafluoro)tell urate (VI). The tetramethylammonium salt was obtained, when trans-dimethoxy tellurium tetrafluoride was reacted with trimethylamine in dichloromethane2. Treatment of these salts with 96% sulfuric acid gave trans-hydroxy methoxy tellurium tetrafluoride. ... 

A similar reaction sequence starting with m-dimethoxy tellurium tetrafluoride, but using imidazole as the base, yielded cis-hydroxy methoxy tellurium tetrafluoride (b.p. 48°/8 torr)1,2. 

Imidazolinium pentafluoro(oxo)tellurate(VI), methanol, and excess imidazole gave imidazolinium d.v-methoxo(tetrafluoro)oxotellurate (VI), which was converted to cis-hydroxy methoxy tellurium tetrafluoride on treatment with 96% sulfuric acid1. 

When a five-fold molar excess of boron trichloride was condensed on cis- or trans-hydroxy methoxy tellurium tetrafluoride and the reaction mixture warmed to 20", hydrogen chloride was liberated. After the hydrogen chloride evolution had ceased, an additional amount of boron trichloride was added. Removal of all volatile materials left the extremely moisture-sensitive boron tris[methoxo(oxo) tetrafluorotellurates (VI)] as residue. The compounds, obtained in quantitative yields, were purified by vacuum distillation3. 

Refluxing cis- or trans-hydroxy methoxy tellurium tetrafluoride with an excess of chlorotrimethylsilane for 12 hours and distilling the reaction mixture, quantitatively produced cis- and trans-methoxy trimethylsiloxy tellurium tetrafluoride3. 

When an excess of tetramethylstannane was condensed on cis- or rran.s-hydroxy methoxy tellurium tetrafluoride and the mixture warmed to 20°, methane was liberated. Stirring the mixture for two hours and briefly heating it to 40°, produced, after evaporation of the excess tetramethylstannane, the colorless, low melting cis- or trans-methoxy trimethylstannoxy tellurium tetrafluoride in quantitative yields. ... 

Cis- and ranj-hydroxy methoxy tellurium tetrafluoride reacted stereospecifically with chlorotrimethylsilane tetramethylstannane, and boron trichloride with elimination of hydrogen chloride or methane. The compounds obtained are trimethylsiloxy methoxy tellurium tetrafluoride trimethylstannoxy methoxy tellurium tetrafluoride, and boron tris[methoxo(oxo)tetrafluorotellurate (VI)]... 

The HjC-O-Te bonds are remarkably stable no cis-trans isomerization was observed when the hydroxy methoxy tellurium tetrafluorides were kept at temperatures below 130°. The bonds are not cleaved by 65% oleum or chlorosulfonic acid at room temperature, instead, the sulfate esters HjCO-TeF tO-SOjH) were formed. These sulfate esters were transformed to HO-TeFiCO-SOjH) upon heating to 100°. Cesium chloride dissolved in an excess of cis- or /run.s-hydroxy methoxy tellurium tetrafluoride liberated hydrogen chloride with the formation of very hygroscopic cesium methoxo(oxo)letrafluorotellurates(VI). Trunj-hydroxy methoxy tellurium tetrafluoride reacts instantaneously with water with loss of fluoride. The cu-compound is stable toward hydrolysis at room temperature. ... 

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