Sulfane preparation

The H2S sulfanes are the subject of several reviews (129,133). Except for hydrogen sulfide these have no practical utiUty. Sodium tetrasulfide [12034-39-8] is available commercially as a 40 wt % aqueous solution and is used to dehair hides in taimeries, as an ore flotation agent, in the preparation of sulfur dyes (qv), and for metal sulfide finishes (see Leather Mineral recovery and processing). 

The lower members of the polysulfane series with n=2-6 have been prepared as pure compounds, while all members with n values up to 35 have been detected by H-NMR spectroscopy in so-called crude sulfane [31]. The gas-phase structures of the first three members of the polysulfane series are well established from either microwave spectra (H2S2 [32], H2S3 [33]) or high-level ab initio MO calculations (H2S4 [34]). Systematic ab initio studies of the structures, vibrational frequencies and heats of formation of H2S with i up to 6 have also been reported [4, 16]. 

Mixtures of polysulfanes H2S are easy to make and probably occur even naturally but the pure compounds are relatively unstable and can therefore be prepared only with some experimental skills and observing certain technical precautions. Detailed prescriptions exist how to make di-, tri-, tetra-, and higher sulfanes in gram quantities. However, as longer the sulfur chain grows as more difficult it becomes to obtain pure compounds. In general, all... 

Disulfane is usually made from a sulfane mixture known as crude sulfane oil while various methods are available for the preparation of the higher sulfanes. Deuterated sulfanes may be prepared by isotopic exchange with DCl [17]. 

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. 

There are a number of other methods to prepare crude sulfane oils, e.g., from hquid H2S and elemental chlorine or bromine [10] or by reaction of H2S with sulfur fluorides [10] or sulfur chlorides [20] but these processes are of httle practical importance. 

The higher sulfanes H2S with n>3 are usually prepared by condensation reactions since their volatihty is low and vacuum distillation is difficult if not impossible. The starting products are the lower sulfanes and certain dichlorosulfanes SmCl2 which provide all members up to octasulfane by reactions of the following types ... 

Hahn and Altenbach designed a method to prepare specific sulfanes with 2 to 5 sulfur atoms in small quantities in solution by the following reactions (RjSi = MePh2Si) [29] ... 

Reactions at Eqs. (12) and (13) are carried out in toluene solution. The yellow crystalline products are purified by recrystallization from pentane and stored in a dry atmosphere at —20 °C. Reaction at Eq. (14) takes place slowly at 20 °C in benzene. The sulfane product H2S is separated from the silylester side product by distillation together with the benzene solvent (in the case of n=2-4) or by phase separation (for n=4, 5). For certain preparative purposes the ester and the solvent may not interfere. If deuterated triflu-oroacetic acid is used in the reaction at Eq. (14) the fully deuterated sulfane is obtained [29]. 

MeO)2S [36]. These evidently originated from the reaction of the dichloro-sulfanes with the methanol solvent used in the preparation of the sulfanes by mixing sodium polysulfide with dichlorosulfanes. 

Older Raman data obtained using a mercury lamp are available for the sul-fanes H2S (n=5-8) and for crude sulfane oil. However, there is some suspicion that the lines observed near 150 and 217 cm result from Ss as a byproduct of the preparation reactions or as a photochemical decomposition... 

The reaction of organic sulfenyl chlorides RSCl or chlorodisulfanes RSSCl with sulfanes provides organic polysulfanes in preparative quantities [2] ... 

The homocyclic sulfur oxide SsO was prepared by condensation of thionylchloride with crude sulfane oil at -40 °C applying the dilution principle. It is believed that the product results from the heptasulfane content of the sulfane oil [88] ... 

Since heptasulfane is difficult to prepare, a mixture of polysulfanes known as crude sulfane oil was used instead (average composition H2S6.2, accessible from sodium polysulfide and hydrochloric acid [71]). From 104 g of... 

On heating the sulfane mixture [C4F9CF(CF3)2]2Sn (average sulfur chain length n = 2.5) with chlorine fca 125 hr at 106°C, the perfluorohexane-2-sulfenyl chloride is formed in appreciable yield 86, 127). The patent literature (5, 19, 87-89,127) abounds with long-chain sulfenyl chlorides prepared according to this latter procedure, but physical data are lacking. 

In their quest for new methods for preparing new sulfur rings 94), Wilhelm and Schmidt 125) studied the simultaneous addition of sulfane and chlorosulfane to cold dry ether,... 

Wilhelm and Schmidt prepared lightly yellow-green solids, containing Sjo rings by reactions of various matching combinations of sulfanes and chlorosulfanes 94,125), e.g.,... 

In order to obtain heterodimers a cysteine residue of one peptide has to be specifically activated for subsequent reaction with the cysteine residue of the second peptide. Thiols are activated by introducing an electron-withdrawing substituent that increases the responsiveness of the sulfur to nucleophilic substitution. This topic has been reviewed 41311 Of the various older methods known in sulfur chemistry for the preparation of unsymmetrical disulfides, i.e. thiosulfates,11321 S-alkylthiosulfonates,11331 5-alkylthiosulfinates,11341 sulfanyl-amines,11351 sulfanylimides,11361 sulfanyl thiocyanates and sulfenyl chlorides,1137,1381 sulfan-... 

The addition of equivalent quantities of a (dialkylamino)trifluoro-/l4-sulfane (see Section 8.4.) to a (dialkylamino)trimethylsilane results in the formation of a bis(dialkylamino)difluoro-/l4-sulfane.71 The dialkylamino moieties of the reactants can be different, resulting in the synthesis of unsymmetrical products. This class of compound is not stable to distillation and is generally utilized without prior purification. For small-scale fluorinations, the bis(dialkylamino)difluoro-/l4-sulfanes are generated in situ, for example, by the addition of one equivalent of commercial-grade DAST to a solution of an appropriate (dialkylamino)trimethylsilane at low temperature.72 73 Examples for the preparation of a bis(dialkylamino)difluoro-/l4-sulfane l71 and dif-luoro-/l4-sulfane 25,11 with different dialkylamino groups are given below. 

A more general synthetic procedure to prepare aryltrifluoro-l -sulfanes. e.g. 4, is the fluorination of an aryl disulfide, e.g. 3, with silver(ll) fluoride, although the cost of the silver(II) fluoride precludes large-scale synthesis.80... 

Compounds having the formula S C12 can be considered as derivatives of the sulfanes, and the higher chlorosulfanes can be prepared by the reaction of S2C12 with sulfanes ... 

The commercially available materials, HC1, (CH3)3A1, and CF3CC>2H, were purified by trap-to-trap distillation in the vacuum line. S03 was generated as needed by passing the vapors from a sample of Sulfan B over a P205 column. Trimethylgallium was prepared by the reaction of gallium with dimethylmercury at 130° C. Difluoramine was prepared by the thiophenol reduction of tetrafluorohydrazine (3). Methyldifluoramine was obtained by fluorinating sodium N-methyl sulfamate. 

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