Sulfur Compounds. 164 Thermal Polymerization of the Cyclic Seleniumsulfide 1,2-Se2S5 Studied by DSC,HPLC, Raman Spectroscopy,and X-Ray Diffraction

Solid 1,2-Se₂S₅ polymerizes endothermically at 47°C to give a linear polymer which after stretching and extraction consists of helical molecules similar to those of polymeric sulfur. Heating of the polymer results in slow exothermic depolymerization at 84°C to give a mixture of seven cyclic Se_nS_8–n molecules which melts at 111°C. When the polymeric Se₂S₅ is refluxed with CS₂ the initial depolymerization Products are 1,2-Se₂S₅, SeS₅ and 1,2,3-Se₃S₅ but in addition SeS₇ and 1,2-Se₂S₆ are formed. These results indicate the atomic sequence –Se? S₅? Se– in the polymer. The powder x-ray diffraction pattern and Raman spectrum of the polymer as well as its lattice parameters are reported and the Probable mechanism of its depolymerization is discussed.