Intramolecularly coordinated low-valent organotellurium complexes derived from 1-(dimethylamino)naphthalene

Abstract

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.