In 1966, Mack report a synthesis of an unsubstituted tellurophene through the reaction of sodium telluride with diacetylene in methanol. This method could be generalised to prepare 2,5-derivatives of tellurophene by selecting a suitably-substituted diacetylene precursor. The product was obtained as a pale yellow liquid with a melting and boiling point of −36°C and 148°C, respectively. Taticchi et al. improved upon this synthesis by using a Schlenk line to exclude oxygen and moisture from the reaction vessel, using pure butadiyne (to decrease unwanted oxidation and polymerization side reactions), and by not using a vacuum to remove the methanol as it leads to loss of the product. This improved procedure allowed the tellurophene to be isolated in 47% yield. Hydrogen telluride (HTe-) and tellurols (RTeH) are implicated in these conversions.
Structure and bonding
The geometry of tellurophene was first determined in 1973 through microwave spectroscopy and has been further refined through X-ray diffraction studies. The Te–C bond length is 2.046 Å and the C–Te–C angle is 82°. These findings are consistent with decreased aromaticity vs that of selenophene and related heterocycles.
Reactivity
Tellurophene forms poly(tellurophene) upon treatment with ferric chloride.
C4H4Te + 2 FeCl3 → 1/n[C4H2Te]n + 2 HCl + 2 FeCl2
The conversion, an oxidative polymerization, is modeled after the corresponding synthesis of polythiophene.
When treated with halogens, tellurophene gives a Te(IV) derivative:
C4H4Te + Cl2 → C4H4TeCl2
Treatment of tellurophene with tert-butyllithium gives 2-lithiotellurophene.
