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)(2)TeI2, 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...O = C 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 C-2nu molecular symmetry but unlike other organotellurium(IV) iodides, the solid state structure of I 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)(2)Te, 3b, prepared by the reduction of the corresponding dibromide, is the first structurally characterized acyclic dialkyltelluride and interestingly, does not involve intramolecular Te...O = C interaction invariably present in the parent dihalides (4-YC6H4COCH2)(2)TeX2 (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)(2)Te, (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. (C) 2004 Elsevier B.V. All rights reserved.