Hexamethyl tellurium

Hexamethyl tellurium is thus far the only known compound of this type. It was obtained from tetramethyl tellurium difluoride and dimethyl zinc2. Hexamethyl tellurium survived being heated at 140° for 4.5 hours. 

Tellurium and dimethylstannane at 20° produced 2,2,4,4,6,6-hexamethyl-l,3,5,2,4,6-tritelluratristanninane when an excess of tellurium was used7, and 2,2,4,4,5,5-hexamethyl-1,3,2,4,5-ditelluratristanninane, when the stoichiometrically required amounts of the reagents were employed8. The heterocycles decompose in air and at elevated temperatures. 

Hexamethyl-l,3,5,2,4,6-tritelluratristanninane3 6.6 g (30 mmol) of dichlorodimethylstannane or 4.94 g (30 mmol) of dimethyl tin oxide in 50 ml of diethyl ether arc reduced to dimethylstannane with 0.76 g (20 mmol) of lithium aluminum hydride. After 1 h, a stream of nitrogen is passed over the reaction mixture and through a cold trap containing more than the stoichiometrically required amount of tellurium cooled in a dry ice/acetone bath. When all volatile material has condensed in the trap it is warmed to 20°, and the mixture is stirred under nitrogen for 3 days. The mixture is then filtered, the solvent is removed from the filtrate under reduced pressure, and the residue is rccrystallized from petroleum ether (b.p. 50-70°) yield 4.8 g (58%) m.p. 78° yellow needles. 

Hexamethyl-l,3,5,2,4,6-tritelluratristanninane All operations are performed under an atmosphere of nitrogen and all solvents are purged with nitrogen prior to use. 3.7 g (29 mmol) of tellurium powder are mixed with 2.3 g (61 mmol) of sodium borohydride and 50 ml of water. The mixture is warmed until all the tellurium has reacted. 6.3 g (29 mmol) of dichlorodimethylstannane dissolved in 25 ml of water are added dropwise to the telluride solution with stirring and the resultant mixture is stirred for 30 min. The greenish-yellow precipitate is collected, dried, and extracted with petroleum ether (b.p. 50-70°) in a Soxhlet apparatus. The extract is cooled to give yellow crystals and the mother liquor is cooled to obtain additional product yield 6.5 g (80%). 

The heavier elements of the group, S, Se and Te all form tetralluorides, EF4 and hexafluorides, EF6- If the central atom in these compounds form Lewis electron pair bonds to all the ligating fluorine atoms, it must accommodate five or six electron pairs in the valence shell, and we refer to the atoms as hypervalent. Sulfur forms no further homoleptic hypervalent derivatives. Selenium forms a solid tetrachloride, but as mentioned in the last paragraph, it decomposes on evaporation. Tellurium forms a solid tetrachloride, which may be evaporated without decomposition, as well as tetraphenyl-, tetramethyl- and hexamethyl- derivatives. 

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