Polysulfide anions

C2h isomer (8) is less well characterized but is said to result from the reaction of hexachlorobutadiene, CCI2 =CC1—CCl=CCl2, with polysulfide anions. The treatment of S2CI2 with [NBu4]2[Zn(o -C3S5)2] yields a mixture of C3Sg and C6S12 which can be separated by fractional crystallization from CS2 ... 

Batsanov et al. 23) reacted sulfur with PtCU and PtBr2 by heating mixtures of the reactants in evacuated, sealed ampoules. At 100 -200°C after 12-24 h, sulfide chlorides PtCljS (1.70 < x < 2 0.6 s y < 3.35) and sulfide bromides PtBr S (1.87 < x 2.06 0.84 y s 1.80) were formed. The compositions depended on the initial PtX2 S ratio, and the temperature. At 320-350°C, loss of chlorine led to the compounds PtClS (1.7 y 1.9). According to their X-ray powder patterns, all of these products retained the main structural features of the original platinum halides. From considerations of molar volumes, the authors deduced the presence of polysulfide anions. 

Since the chain-lengths of the molecules present in crude sulfane oil is different from the chain-length of the anions in the original sodium polysulfide solution one has to conclude that in addition to the reaction at Eq. (4) the reactions at Eqs. (5) and (6) also take place during the preparation by protonation of the polysulfide anions. 

Interestingly, the sulfanes H2S are both proton acceptors and donors. In the first case sulfonium ions H3S are formed, in the second case hydrogen polysulfide anions HS are the result. While the latter have never been isolated in salts, several salts with sulfonium cations derived from the sulfanes with n = 1, 2, and 4 have been published. However, none of these salts has been structurally characterized by a diffraction technique. Therefore, the structures of the HsSn cations and HS anions are known from theoretical calculations only. 

Abstract Inorganic polysulfide anions and the related radical anions S play an important role in the redox reactions of elemental sulfur and therefore also in the geobio chemical sulfur cycle. This chapter describes the preparation of the solid polysulfides with up to eight sulfur atoms and univalent cations, as well as their solid state structures, vibrational spectra and their behavior in aqueous and non-aqueous solutions. In addition, the highly colored and reactive radical anions S with n = 2, 3, and 6 are discussed, some of which exist in equilibrium with the corresponding diamagnetic dianions. 

Furthermore, polysulfide anions are subject to autoxidation if molecular oxygen is present, e.g. ... 

Therefore, the pH values of these solutions are between 11 and 12. The speciation model used by 8chwarzenbach and Fischer is certainly too simple but these authors have been the first to demonstrate the strong dependence of the polysulfide anion distribution on the alkalinity. According to Eqs. (26)-(28) higher pH values in dilute solutions will favor smaller anion sizes. 

Ionic polysulfides dissolve only in media of high polarity hke water, liquid ammonia, alcohols, nitriles, amines, and similar solvents. In all of these solvents 8 can be reduced electrochemically to polysulfide anions. On the other hand, the electrochemical oxidation of polysulfide anions produces elemental sulfur ... 

The solvothermal reaction between metal halides and polysulfide anions is also a useful method for the synthesis of metal-polysulfide clusters. Hydrothermal reaction of K2PtCl4 with K2S4 (5 eq) at 130 °C in a sealed tube... 

Copper(I) sulfide reacts with polysulfide anions in aqueous solutions forming soluble copper polysulfides. 

The majority of polysulfide anions have acyclic structures. The configurations of S2 species are in accord with their bond valence (b) ... 

Upon discharge sodium ions diffuse through the sodium-conducting /J- or -alumina or NASICON -> solid electrolyte. On the outer surface of the solid electrolyte they react with molten sulfur and/or low valency sulfide anions forming negatively charged polysulfide anions. The rather low electric conductivity of molten sulfur is improved by addition of tetracyanoethylene... 

The Final Analysis. The SEM analysis of the liquid extrusion shows that sulfur is present in quantities much greater than the monosulfide of calcium could provide. The most probable explanation is that part of the sulfur is present in polysulfide anions, as the infiltration conditions appear to favor their formation (18). A sample of the yellow solution obtained by leaching fragments under nitrogen was therefore analyzed by laser Raman spectrometry to determine if the absorption... 

Dissociation of the polysulfides yields an alkaline solution which, together with dissolved Ca(OH)2, increases the pH of the surrounding medium to the point where incoming polysulfide anions can remain in solution. If the system is closed or under an inert atmosphere, precipitation will cease, and the concentration of polysulfides in the surrounding liquid will gradually increase as sulfur is removed from the concrete. 

This area continues to provide many new compounds and structures, reflecting the versatility and thermodynamic stability of polysulfide anions. Most of the compounds are described under the appropriate metal elsewhere in the Encyclopedia, some of the most elegant recent developments have been with other p-block elements such as tellurium, bismuth, and antimony. ... 

AUcyl chlorides, -bromides, and -iodides can be converted to tri- or tetrasulfanes by treatment with elemental sulfur at 20 °C in the presence of KOH and traces of water methyl-, ethyl-, isopropyl-, and allylpolysulfanes have been prepared in this manner. Sometimes hydrazine is added to rednce Sg to polysulfide anions. ... 

The reactions of equation (99) usually proceed quantitatively to the right and without any side reactions. The advantage of (1) over sodium pentasulfide is not only that it is soluble in organic solvents (CS2, CH2CI2) and does not equilibrate with other ring sizes, but also that it does not introduce nucleophihc polysulfide anions that catalyze decomposition and interconversion reactions (see Section 5.1). 

A great variety of binary Mo-S complex anions is formed and can be isolated in reactions of the tetrathiomolybdate anion [MoS ] " with various suinde and polysulfide anions. The nature of the anionic products that can be isolated from these reactions depends on (a) the amount of excess sulfur used (and the types of ligands present in the reaction mixtures), (b) the type of counterion used in the isolation of the complex anions, and (c) the type of solvent employed in the synthetic procedure. In a recent article, we described a scheme that interrelates the various [Mo2(S),(S2)6-,] anions. In this scheme (Fig. 1), any of the six homologs can hypothetically be obtained from any other by either the addition of sulfur, or the abstraction of sulfur by triphenylphosphine. Experimentally, the correctness of this scheme has been verified by the successful synthesis of most of the [Mo2(S) (S2)6 ] complexes, or of their internal redox isomers. In the [Mo2(S), (82)6 series, the homologs with n = 4, 5, and 6 have been characterized structurally. Those with n = 2 and 3 have been characterized structurally as the internal-redox isomers, [(S4)Mo(S)(//-S)2(S)Mo S2)] (ref. 3) and... 

Marcasite forms below about pH 5, when the neutral, undissociated polysulfide acids dominate, whereas pyrite is favored at pH values above 6, when polysulfide anions are the major species (Fig. 12.15). Schoonen and Barnes (1991a) offer detailed explanations for such complex behavior. 

Oxygen forms a double bond that is three times more stable than its single bond. Owing to this tendency to form strong double bonds, it is very unlikely that longer-chain polyoxygen anions would exist. Sulfur is much less likely to form 7t bonds and therefore more likely to generate catenated polysulfide anions. 

Since the aqueous sodium polysulfide contains already several polysulfide anions in equilibrium and since the acidification results in some interconversion reactions, a sulfane mixture H2S c is obtained rather than pure H2S4. This mixture nevertheless reacts in dry CS2/Et20 mixture at 20 °C with dichlorodisulfane, besides other products, to S12 which has been isolated in 4% yield by extraction with CS2 and fractional crystallization [41] ... 

Autoxidation of aqueous H2S solutions results in elemental sulfur, sulfite, thiosulfate, and eventually sulfate. However, under certain conditions monodispersed sulfur sols with particle diameters of between 0.2 and 1.2 /um are obtained [48]. For example, a solution of H2S of concentration 46 mmol 1 in pure H2O exposed to air at 25 °C became turbid after an induction period of ca. 8 h and then showed briUiant higher-order Tyndall spectra. A solution saturated in H2S exhibited a pH value of 4.1 and was rapidly oxidized in an atmosphere of pure O2. At pH values >8 no elemental sulfur was formed (clear colorless solution), in the range pH=7-8 yellow solutions were obtained (polysulfide anions), while at pH<7 turbid solutions were produced but the induction period was as longer as lower the pH value [48] ... 

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