Electrophilic substitution of acetyltrimethylsilane with tellurium(IV) halides: A synthetic route to 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides

• Reactions of acetyltrimethylsilane with TeX4 gave novel silylated heterocycles 3-Methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides.
• Oxidative addition of dihalogens to these heterocycles affords the corresponding oxatellurolylium trihalides.
• 125Te chemical shifts for 3-Methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides are among the highest (downfield) reported for organotellurium(II) compounds.
• A large lowering of ν(CO) indicating a strong Te…OC interaction is substantiated by X-ray structural data for 3-Methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium chloride.

The reaction of tellurium tetrahalides, TeX4 (XCl. Br) with acetyltrimethylsilane in CCl4 at ambient temperature, unlike that of the aryltellurium trichlorides, ArTeCl3 that give the expected electrophilic substitution products, Ar(Me3SiCOCH2)TeCl2, (Ar = 1-C10H7, 2; 2,4,6-Me3C6H2, 3), afforded novel silylated heterocycles, 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides 1a and 1b. These Te(II) heterocyclic compounds undergo halide exchange with sodium iodide and also add dihalogens oxidatively to afford the corresponding iodide, 1c and the Te(IV) trihalides, 5a and 5b respectively. A large lowering of ν(CO) is indicative of strong Te⋯OC interactions among these heterocycles, and is also substantiated by single-crystal X-ray diffraction data for 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium chloride. The 125Te chemical shifts for the new 10-Te-3 telluranes and 12-Te-5 pertelluranes that involve tellurium bound to two highly electronegative atoms (O, X) are among the highest (downfield) reported for organotellurium(II) and (IV) compounds.

Reaction of tellurium tetrahalides with acetyltrimethylsilane afforded novel silylated heterocycles, 3-methyl-5-(trimethylsilyl)-1,2-oxatellurol-1-ium halides. A strong Te⋯OC interaction among these heterocycles is indicated by a large lowering of ν(CO) and short (C)O⋯Te bond distance.Figure optionsDownload as PowerPoint slide