Electrophilic substitution reactions of 2-acetylpyridine, 2-acetylpyrrole & cyclohexanone: Isolation and molecular structures of novel organotellurium(IV) chlorides

Chloro analogs of novel organotellurium(IV) compounds (1a, 2Aa, 2Ba, 3Aa & 3Ba) have been synthesized by using electrophilic substitution reactions. The 2-pyridoylmethyltellurium(IV) trichloride, PyCOCH2TeCl3; 1a (Py = 2-C5H4N, 1) has been prepared by the condensation reaction between the parent methyl ketone (PyCOCH3) and TeCl4. Aryl(2-pyrrolylmethyl)tellurium(IV) dichlorides, Ar(PyrrCOCH2)TeCl2; 2Aa, 2Ba (Pyrr = 2-C4H4N, 2; Ar = 1-C10H7, Npl, A; 2,4,6-Me3C6H2, Mes, B) and aryl(2-oxocyclohexyl)tellurium(IV) dichlorides, Ar(Cyl)TeCl2; 3Aa, 3Ba (Cyl = 2-C6H9O, 3) have been prepared by electrophilic substitution reaction of NplTeCl3 or MesTeCl3 with 2-acetylpyrrole and cyclohexanone respectively. Formation of tellurium(IV) trichloride (PyCOCH2TeCl3, 1a) corresponds to a category of compound which are rarely obtained using this methodology. Structural aspects of Te(IV) compounds 1a, 2Ba and 3Ba have been studied using single crystal X-ray diffraction technique. Crystallographic studies of 1a has indicated a preference of the 2-pyridoylmethyl moiety for the small-bite (C, N) chelation resulting in the 1,5 Te⋯N hypervalent interaction while in PyrrCOCH2MesTeCl2, 2Ba; 2-pyrrolylmethyl moiety (C, O) chelation over less strained (C, N) coordination is preferred. In 3Ba, 1,4 Te⋯O intramolecular secondary bonding interaction (SBI) has appeared.