Intramolecularly coordinated low-valent organotellurium complexes derived from 1-(dimethylamino) naphthalene
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A series of low-valent intramolecularly coordinated organotellurium compounds incorporating the 8-(dimethylamino)-1-naphthyl group has been synthesized by the organolithium route. Insertion of elemental tellurium into the Li-C bond of RLi (2) affords the tellurolate RTeLi (3) (R = 8-(dimethylamino)-1-naphthyl). Oxidative workup of 3 gives dark red ditelluride 4 in moderate yield. Reaction of 2 with ''PhTeBr'' afforded telluride 5. Interestingly, the reaction of 2 with TeI2 afforded the stable tellurenyl iodide 6 instead of the expected telluride R(2)Te. Controlled bromination of ditelluride with bromine in chloroform gave stable tellurenyl bromide 7 whereas bromination with excess bromine leads to the isolation of tellurium(IV) tribromide 8. Ditelluride 4 was found to be inert to the reactions with diazomethane and reducing agents like NaBH4, NaH, and LiAIH(4). The compounds were characterized by elemental analysis, NMR (H-1, C-13, Te-125), and mass spectroscopic techniques. For three of these compounds R(2)Te(2) (4), RTePh (5), and RTeBr (7) the molecular structures in the solid state have been determined by X-ray diffraction studies. All the three complexes which have been structurally characterized have a T-shaped geometry around the central tellurium atom. Though there are weak Te ... N interactions in the solid state, in solution pyramidal inversion at the N-center is not blocked and as a result, the NMe(2) signals are observed as sharp singlets in the H-1 NMR spectra.
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