Selenium sulfur dihalides, ChnX2 (n = 1, 2, 3; Ch = Se, S; X = Br, Cl). Raman and 77Se NMR spectroscopic characterization

Abstract

Solutions of Se2Cl2 in S2Cl2, Se2Br2 in S2Cl2, Se in S2Cl2, and S in Se2Cl2 have been studied by Raman and 77Se NMR spectroscopy. Selenium sulfur dihalides, SeSCl2, SeSBr2, and SeSBrCl, formed in these solutions, have been shown by Raman and 77Se NMR spectroscopy to have chain structures. Solutions of Se2Cl2 in S2Cl2, S in Se2Cl2, and Se in S2Cl2 have been shown to contain, in addition to Se2Cl2, S2Cl2, SeSCl2, Se3Cl2, and S8, trichalcogen dichlorides Se2SCl2 and SeS2Cl2. Selenium-77 signals corresponding to all seven chain isomers of the expected Se-containing dichalcogen dihalides, Se2Br2, Se2Cl2, Se2BrCl, SeSCl2, SeSBr2, BrSeSCl, and ClSeSBr, have been observed in the spectrum of a 1:1 molar mixture of S2Cl2 and Se2Br2. The disulfur dichloride and dibromide, as well as the bromide chloride, are also present. Selenium–bromine and sulphur–chlorine linkages are observed to be preferred over selenium–chlorine and sulphur–bromine bonding in these mixtures. The 77Se chemical shifts correlate well with the electronegativity of the directly bonded neighbour but inversely with that of the next-nearest neighbour. Keywords: selenium halides, sulfur halides, low valent chalcogen halides, 77Se NMR, Raman spectroscopy.