Secondary bonding in functionalized organotellurium compounds: preparation and structural characterization of bis(acetamido)tellurium(IV) diiodide and bis(4-methylbenzoylmethyl)tellurium(II)

Elemental tellurium inserts, under mild conditions, between C–I bond of iodoacetamide to afford bis(acetamido)tellurium(IV) diiodide (NH2COCH2)2TeI2, 1. Heating of N-bromomethylphthalimide with activated tellurium powder however, resulted in the formation of bis(phthalimido)methane, 2, instead of the expected product bis(phthalimidomethyl)tellurium(IV) dibromide. The IR spectrum of 1 is indicative of intramolecular Te⋯Odouble bond; length as m-dashC interaction which is also substantiated by its single-crystal structure. The compound with planar small-bite chelating organic ligands acquires butterfly shape that imparts almost perfect C2v molecular symmetry but unlike other organotellurium(IV) iodides, the solid state structure of 1 is devoid of any intermolecular Te⋯I or I⋯I secondary interactions owing to the presence of intramolecular Te⋯O secondary bonds as well as intermolecular N–H⋯O, N–H⋯I and C–H⋯I hydrogen bonds. Bis(4-methylbenzoylmethyl)telluride (4-MeC6H4COCH2)2Te, 3b, prepared by the reduction of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve intramolecular Te⋯Odouble bond; length as m-dashC interaction invariably present in the parent dihalides (4-YC6H4COCH2)2TeX2 (Y = H, X = I 4a; Y = H, X = Br 5a; Y = MeO, X = Br 5c). Weak intermolecular Te⋯Te and C–H⋯O hydrogen bonds appear to be the non covalent intermolecular associative forces that dominate its crystal packing in the solid state of this Te(II) derivative. The dialkyltellurides (4-YC6H4COCH2)2Te, (Y = H, 3a, Me, 3b) undergo oxidation in presence of (SCN)2 to give the corresponding bis(isothiocyanato)tellurium(IV) derivatives and form 2:1 adducts with Pt(II) and Pd(II) chlorides.