Intramolecularly Coordinated Low-Valent Organotellurium Complexes Derived from 1-(Dimethylamino)naphthalene

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 R2Te. 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 LiAlH4. The compounds were characterized by elemental analysis, NMR (1H, 13C, 125Te), and mass spectroscopic techniques. For three of these compounds R2Te2 (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 NMe2 signals are observed as sharp singlets in the 1H NMR spectra.