Tellurium-containing chalcogen rings

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(x)S(8-x)(x=1,2) and Te(x)Se(y) S(8-(x+y)) (x=1;y=1,2) at HF/3-21G* level of theory. Each molecule is a crown-shaped eight-membered ring like Sg 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 Moller-Plessett perturbation theory. The most stable species are TeS(7), 1,2,-Te(2)S(6), 1,2-TeSeS(6), and 1,2,8-TeSe(2)S(5). The calculations are consistent with the observation that 1,2-Te(2)S(6) and 1,2-TeSeS(6), are initially formed when [Ti(MeC(5)H(4))(2)(Te(2))(2)Ti(MeC(5)H(4))(2)] or [Ti(MeC(5)H(4))(2)(Te(x)E(2-x))(2)Ti(MeC(5)H(4))(2)] (E=S, Se) are treated with chalcogen chlorides. When (Me(3)Si)(2)Te is treated with ClSeS(5)SeCl, 1,2,8-TeSe(2)S(5) is formed. All these products decompose on standing with the formation of TeS(7) and some insoluble material.