4,4-Diorganyl-1,1,3,6-tetrachloro-1,4-tellura(IV)silafulvenes – New class of tellurium–silicon containing heterocycles

The reaction of TeCl4 with diorganyl diethynyl silanes RR1Si(Ctriple bond; length of mdashCH)2 in CHCl3 at room temperature leads to regio- and stereoselective formation of a new class of unsaturated five-membered heterocycles, 4,4-diorganyl-1,1,3,6-tetrachloro-1,4-tellura(IV)silafulvenes, in high yields. In the case of dialkyl substituents at the silicon atom the reaction proceeds with 100% stereoselectively to afford only E-isomers, while for cyclic diethynyl silanes the spiro-heterocycles formed have Z- and E-configurations, E-isomers being the predominant ones. Structures of the heterocycles have been proved by the multinuclear (1H, 13C, 29Si, 125Te) NMR spectroscopy, 2D NOESY NMR spectroscopy and mass-spectrometry. Z-Isomers are characterized by a long-range spin–spin interaction of protons through five bonds with 5JHH 0.2–0.5 Hz lacking in E-isomers. In the mass spectra the heterocycles manifest themselves as the fragment ions [M−Cl2]+.