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Syntheses and Characterization of Some Mixed Te/Se Polychalcogenide Anions [TemSen]2-

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posted on 2004-08-23, 00:00 authored by Perumal Sekar, James A. Ibers
Several mixed Te/Se polychalcogenide anions [TemSen]2- were synthesized at 293 K by reactions between Ten2-and Sen2- anions in N,N-dimethylformamide (DMF) in the presence of different-size ammonium or phosphonium cations, in some cases in the presence of metal species. The structures of these anions were determined by single-crystal X-ray diffraction methods. The crystal structures of [NEt4]2[Te3Se6] (1) and [NEt4]2[Te3Se7] (2) consist, respectively, of one-dimensional infinite [Te3Se62-] and [Te3Se72-] anionic chains separated by NEt4+ cations. In compound 1, each chain comprises Te3Se5 eight-membered rings bridged by Se atoms. The Te3Se5 ring has an “open book” conformation. The NMR spectrum of a DMF solution of [NEt4]2[Te3Se6] crystals at 223 K shows 77Se resonances at δ = 290, 349, and 771 ppm and a single 125Te resonance at δ = 944.7 ppm. In compound 2, each chain comprises Te3Se6 five- and six-membered rings bridged by Se atoms. The Te3Se6 ring can be regarded as an inorganic analogue of bicyclononane. The anion of [PPh4]2[Te2Se2] (4) contains a Se−Te−Te−Se chain with the terminal Se atoms trans to one another. The new compounds [PPN]2[TeSe10] (3), [NMe4]2[TeSe3]·DMF (5), and [NEt4]2[TeSe3] (6) contain known anions.