The disproportionation of diselenium dichloride, Se₂Cl₂, and diselenium dibromide, Se₂Br₂

Abstract

Thispaper is dedicated to Professor Ronald J . Gillespie on the occasion of his 65th birthday MARC LAMOUREUX and JOHN MILNE. Can. J. Chem. 67, 1936Chem. 67, (1989.Diselenium dichloride and dibromide have been shown by Raman and 77Se-nmr spectroscopy to be equilibrium mixtures of Se2X2 and small amounts of Sex2 and Se,X2. Equilibrium constants have been estimated for the disproportionation reactions,The origin of "spurious" peaks in the reported vibrational spectra of Se2Br2 and Se2C12, which have been variously assigned to overtone and combination bands and impurities has been clarified. Mixtures of Se2Br2 and Se2C12 are shown to contain Se2BrCl in equilibrium according to Se2Br2 + Se2C12 = 2Se2BrCI

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

“…1 and consists of peaks at 441, 414, 369, 190, and 170 cm-I. ' The peak at 414 cm-I is coincident with v(SeC1) of SeCl, but is 4 times stronger than that expected for the equilibrium concentration of SeCl, present (2). The observation of both SC1 (441 cm-I) and SeCl (369 cm-I) stretching bands as well as the SeS (414 cm-I) stretching band is consistent with the formation of the chain isomer of SeSCl,.…”

“…Diselenium dichloride was prepared from stoichiometric amounts of Se and SeC1, (2) and Se,Br, was prepared from HBr (Fisher, 48%), SeO, (Aldrich), and Se (Baker analyzed) by the method of Lenher and Kao (5). Moisture sensitive mixtures were made up by weighing in a dry box at ambient temperature.…”

“…In addition, however, three peaks at 477, 221, and 152 cm-I are observed, which correspond to the three strongest bands of elemental sulfur, S,, dissolved in S2C12, (lo), and as discussed below, in Se,Cl,. Thus, Se dissolves readily in S,Cl, according to and some SeSCl, is formed by equilibrium [2]). The spectrum of a 1 : 1 molar mixture of S in Se,Cl,, shown in Fig.…”

“…Recently SezClz and Se,Br, were shown to contain equilibrium amounts of Sex,, Se,X,, and Se,X, (2). The mixed halogen compounds, Se,,BrCl (n = 1,2) have also been reported (2) but mixed chalcogen dihalides have received little attention although sulfur selenium chains in general are currently of great interest (3).…”

“…and Se,CI, with S was undertaken as part of an ongoing study of low-valent Se halide chemistry (2,6).…”