125-Tellurium and 77-selenium multinuclear magnetic resonance studies of Te 6 4+ , Te 4–n Se n 2+ , Te 2 Se 4 2+ , and Te 3 Se 3 2+ polyatomic cations

High-resolution 125Te and 77Se Fourier transform n.m.r. spectroscopy has been used to characterize the previously known Te64+, Te42+, Se42+, and Te2Se42+ cations for the first time and several new mixed species in the +1/2 (Te3Se2+, cis- and trans-Te2Se22+, and TeSe32+) and +1/3 (Te3Se32+) oxidation states; the 125Te–123Te, 125Te–77Se, and 77Se–77Se spin–spin couplings have been observed in both natural abundance and 94·4%77Se enriched preparations and used to assign the structures.