New Finding in the Chemistry of the Lower Oxides of Sulfur

Abstract

Important advances have recently been made in the chemistry of the lower oxides of sulfur, both in the preparative sphere and by the application of modern physical methods of in-vestigation. In this paper the knowledge gained to date on the compounds SO, S202, s20, S203, and the polysuljiur oxides is reviewed and critically appraised. DefinitionIn the present paper, the term "lower o x i d e s of s u lfur" refers to oxides in which the oxidation number z of suIfur is < 2. Thus, although S2O3 is discussed briefly, it does not belong to this group, particularly since the sulfur in this compound is evidently present in two very different oxidation states. However, the term does encompass the oxides SO, S 2 0 2 , S 2 0 , and the polysulfur oxides of general formula (S,O), in which n > 2. According to their properties, compounds containing hydrogen in addition to sulfur and oxygen should be grouped together with the polysulfur oxides. These compounds will be referred to as polysulfane oxides. SO (likeS2) is present in an appreciable concentration only at high temperatures. The enthalpy of formation of sulfur monoxide is found by investigation of equilibria such as those shown in Equations (b) and (c) [9, lo]. 2 SO2 7 ' SO --SO3 at 1500°C (b) AH: = +48.6 kcal/mole of SO SOz f 1/2 Sz T' 2 SO at 1250 "C (c) AH:+58.3 kcal/mole of SO2

Thermolysis of thiete 1,1-dioxide and related species

“…The remaining sulfur is extruded as SO and was observed as a red material on the Dewar surface which was transformed into a yellow insoluble polymer on being warmed to room temperature. This behavior is compatible with the disproportionation,of sulfur monoxide to disulfur monoxide and conversion of the latter to poly(su1fur oxide) (27).…”

The Thermal Decomposition of S2O Forming SO2, S3, S4 and S5O − An ab initio MO Study

“…[1] The calculated NBO atomic charges of the S 2 Figure 2 will result. However, the corresponding reactions given in Equations (5) and (6) are predicted to be strongly endothermic.…”

“…S 2 O is also formed in numerous redox reactions between reduced sulfur compounds and oxidizing agents as well as in thermal decomposition reactions of sulfur-rich sulfane oxides and sulfur oxides. [1] S 2 O can be obtained in a practically pure form by the heterogeneous reaction of thionyl chloride vapor with solid silver sulfide at 160°C and low pressures, see Equation (1). [2] SOCl 2 ϩ Ag 2 S Ǟ S 2 O ϩ 2AgCl (1) More recently, S 2 O has seemingly been generated in solution by thermal decomposition of suitable organic precursors (e.g., sulfane oxides) or of S 8 O, and the S 2 O unit [3Ϫ5] and its decomposition product S 3 [5] have been trapped in situ by addition reactions with either unsaturated transition metal complexes [3] or with olefins, dienes or diazoalkanes.…”

“…[1] S 2 O can be obtained in a practically pure form by the heterogeneous reaction of thionyl chloride vapor with solid silver sulfide at 160°C and low pressures, see Equation (1). [2] SOCl 2 ϩ Ag 2 S Ǟ S 2 O ϩ 2AgCl (1) More recently, S 2 O has seemingly been generated in solution by thermal decomposition of suitable organic precursors (e.g., sulfane oxides) or of S 8 O, and the S 2 O unit [3Ϫ5] and its decomposition product S 3 [5] have been trapped in situ by addition reactions with either unsaturated transition metal complexes [3] or with olefins, dienes or diazoalkanes. [4,5] These fascinating developments may result in a renaissance of S 2 O chemistry in solution, although it must be stressed that this molecule has never been observed directly (e.g., spectroscopically) in liquid solutions.…”

“…[6] The reactivity of S 2 O has not been studied systematically, probably due to its thermal instability. [1] On condensation of gaseous S 2 O at low temperatures, by dissolution in cold inert solvents or by increasing its partial pressure in the gas-phase at room temperature to values above 1 mbar, S 2 O decomposes rapidly. [1] The final decomposition products of S 2 O are elemental sulfur (S 8 ) and sulfur dioxide but the following intermediates have been observed under differing reaction conditions (in chronological order):…”