Tellurium-containing Chalcogen Rings

Abstract

The possibility for the existence of the tellurium-containing chalcogen ring molecules has been explored by use of ab initio molecular orbital techniques. The full geometry optimization has been carried out for all isomers in the series Te_xS_8–x(x=l,2) and Te_xSe_yS_8–(x+y) (x=l;y=1,2) at HF/3-21G^* level of theory. Each molecule is a crown-shaped eight-membered ring like S₈. All calculated bond parameters indicate single bonds and agree with experimental parameters where available. The relative stabilities of the different isomers have been calculated by taking the effects of electron correlation into account involving the second-order Møller-Plessett perturbation theory. The most stable species are TeS₇, 1,2,-Te₂S₆, 1,2-TeSeS₆, and 1,2,8-TeSe₂S₅. The calculations are consistent with the observation that 1,2-Te₂S₆ and 1,2-TeSeS₆, are initially formed when [Ti(MeC₅H₄)₂(Te₂)₂-Ti(MeC₅H₄)₂] or [Ti(MeC₅H₄)₂(Te_xE_2-x)₂Ti(MeC₅H₄)₂] (E=S,Se) are treated with chalcogen chlorides. When (Me₃Si)₂Te is treated with ClSeS₅SeCl, 1,2,8-TeSe₂S₅ is formed. All these products decompose on standing with the formation of TeS₇ and some insoluble material.