REACTIVITY OF 1,1'-SPIROBI(3H-2,1-BENZOXATELLUROLE)-3,3'-DIONE [10-TE-4(C2O2)] WITH ORGANIC PHOSPHORUS REAGENTS - THE FIRST SYNTHESIS OF A TELLURANE WITH 2 CARBON-TELLURIUM AND 2 SULFUR-TELLURIUM BONDS, 1,1'-SPIROBI(3H-2,1-BENZOTHIATELLUROLE)-3,3'-DIONE [10-TE-4(C2S2)]

A new spirotellurane, 1,1'-spirobi(3H -2,1-benzothiatellurole)-3,3'-di one [10-Te-4(C2S2)] (2), having two sulfur atoms as the apical ligands and two carbon atoms as the equatorial ligands was obtained by the re action of the spirotellurane 1 with Lawesson's reagent. The treatment of 2 with aqueous NaOH gave an unsymmetrical spirotellurane 4. The tel luranes 1 and 2 underwent ring-opening reactions on treatment with P(N Et(2))(3) to afford the telluride 6.