Polysulfides halides

Complexes with chelating polysulfidc ligands can be made either by reacting complex metal halides with. solutions of polysulfides or by reacting hydrido complexes with elemental... 

Although belonging to a slightly different class of reactions, the reaction of trifluoromethyl radicals with sulfur vapor has been shown to provide a route to trifluoromethyl polysulfide compounds (20). Instead of using sulfur halides, which undoubtedly would also give positive results, elemental sulfur (Ss) was vaporized and dissociated into atomic and polyatomic sulfur species. 

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. 

Very often inorganic polysulfides have been used to synthesize organic polysulfanes by reaction with, for example, alkyl or aryl halides [109, 110], e.g. ... 

Reactions of Metal Halides with Polysulfide Dianions. 166... 

Reactions of metal halides with polysulfide dianions are useful methods for the synthesis of polysulfido complexes of main group elements and transition metals. In most of these reactions, similarly to other methods, the chain lengths and coordination types of the polysulfide ligands depend on the other ligands coordinated to the metal, on the ratio between the metal and sulfur, on the reaction temperature, and other parameters. 

Scheme 20 Synthesis of group 13 polysulfido complexes by the reaction of the corresponding metal halides with polysulfide dianions...

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... 

It is supposed to originate from the dissociation of 84 . This dissociation is perhaps significant at high temperatures, like those of the synthesis of ultramarine pigments or those of doping of alkali halide crystals. 83 and 82 radicals have also been observed in the alkali halides doped with sulfur [30, 31]. Another radical anion polysulfide, 84 , has been identified, by EPR experiments, in solution in DMF, originating from the dissociation of 8g , which is the least reduced polysulfide in this solvent [32]. 

The unsaturated derivative of 1,2,3,4-tetrathiocane (401) has been prepared by the halide route with sodium polysulfide (72JOC2367). 

The potentiometric measurement of hydrogen sulfide via a Ag/Ag2 electrode is well known and such electrodes are commercially available. Boulggue (22) has used the electrode to measure changes in potential during a titration with HgC. This method can measure sulfide, polysulfide, thiols, sulfite and thiosulfate. Weaknesses of die method are the following there is no method of sample preservation the pH must be adjusted to pH 13 for the measurement of sulfide, thiol and polysulfide then adjusted to pH 7 for the measurement of thiosulfate and sulfite polysulfide is determined by difference after attack on the polysulfides with added sulfite (if elemental sulfur is present in the sample it will also participate in this reaction) the identity of the organic thiols is unknown and sulfite can not be measured in seawater samples because of competition with halides (21). 

Normally made by interaction of ions or halides with alkali polysulfides, they can be formed from sulfur, as in the reaction ... 

Perfluoroalkylmercury compounds have been prepared by reaction of perfluoroalkyl halides with cadmium amalgam or by reaction of fluoroalkenes with mercury(II) fluoride. Due to the high thermal stability of perfluoroalkylmercury compounds, they can be sublimed from concentrated sulfuric acid without decomposition and are of limited synthetic utility. These reagents have found use as difluorocarbene sources and do react with elemental sulfur at elevated temperatures to afford thioacid fluorides, di- and polysulfides, and thioketones. ... 

Reaction of Organic Halides or Sulfenyl Chlorides with Titanocene Polysulfides... 

Alkylation of an ethanolic solution of sodium sulfide containing an equivalent amount of dissolved sulfur produces disulfides in 60-80% yields from alkyl" or o- and p-nitrophenyl halides." Cyclic disulfides are prepared by alkylation with 1,3-dihalides." Hydroxyl" and nitro" groups do not interfere. Alkylation of a solution of sodium sulfide containing 2-5 equivalents of sulfur produces polysulfides. 

Symmetrical disulfides (73) may be prepared by reaction of alkyl halides with disodium disulfide (Scheme 43). The product is contaminated with triand polysulfides owing to the presence of impurities in the disodium disulfide however, lower members of the series of dialkyl disulfides may be purified by fractional distillation. Disulfides can also be obtained from thiols by mild oxidation, e.g. by treatment with iodine or dimethyl sulfoxide (DMSO) (Scheme 44). In the reaction with iodine, the hydriodic acid formed must be removed, otherwise the disulfide is largely reduced back to the thiol by hydriodic acid which is a powerful reducing agent. Pure unsymmetrical disulfides are more difficult to prepare owing to their tendency to undergo disproportionation they can, however, be synthesised from thiols by treatment with imides (see p. 59) or sulfenyl halides (51) (Scheme 45). 

Carbon disulfide is a valuable synthon (see Chapter 9, p. 147) which can be used for the synthesis of thiocarbonic acid derivatives. Thus, carbon disulfide reacts with ammonium polysulfide or hydrogen sulfide to give trithiocarbonic acid (70) or symmetrical esters (73) after reaction with an alkyl halide. With alkoxides or thiolates, carbon disulfide forms xanthates (77) or S-alkyl trithiocarbonates the latter by further treatment with alkyl, acyl or diazonium halides affords the derivatives (74)-(76) (Scheme 39). 

The HOMO of OH" is higher than the LUMO of I2, which indicates that two-electron transfer from OH to I2 should be facile. However, the reaction is reported to be slower in seawater, and I2 appears to react with reduced organic matter (21-23). HOI in turn reacts with organic matter to produce I" and RI (3, 24). Thus iodide oxidation leads to electron acceptors as intermediates that can eventually re-form iodide. In contrast, sulfide oxidation leads to strong electron donors such as the polysulfides, which oxidize back to SO/ , as the intermediates (25). Thus, halides and sulfide have a significant difference in their environmental cycling, despite their isoelectronic nature. 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfides (e.g. TI2S5) and poly iodides, etc. In other respects Tl resembles the more highly polarizing ion Ag" ", e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

For these and other reasons it seems improbable that H2S" is a correct formulation for either of these radicals. Possible alternatives include H2S+, isoelectronic with PH2, and species such as H2S2", H2S2 or more complex polysulfide radicals. The radical H2S+ is a possible candidate for the species in alkali halide crystals (56), which apparently contains only one sulfur atom, except that some restricted rotational motion would need to be invoked to explain the equivalence of the two protons. Rotation within the molecular plane would achieve this, and would also account for the form and magnitude of the anisotropic proton coupling. The 33S tensor is also accommodated reasonably well, as also is the positive g-shift. However, the very large value for Ag is more difficult to reconcile with this formulation. 

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