Sulfur in liquid ammonia

Benzopentathiepin (3, R1 =R2 = H) is produced in 54% yield from 1,2,3-benzothiadiazole and sulfur402 and in 97% yield from 1,3-benzodithiole-2-thione and sulfur in liquid ammonia in the presence of 1,3-dinitrobcnzcnc.403 These methods have also been used for the preparation of various substituted benzopentathiepins 3. 

Some illustrative examples of the application of 14N NMR spectroscopy in sulfur-nitrogen chemistry include (a) studies of the (NSC1)3<->3NSC1 equilibrium in solution28 and (b) identification of the S-N species present in solutions of sulfur in liquid ammonia.29... 

Sulfur and nitrogen form a variety of binary anions with acyclic, cyclic and cage structures.69,70 The Se-N anions are only known in metal complexes. S-N anions play an important role in the formation of cyclic sulfur imides and as constituents of solutions of sulfur in liquid ammonia. 

The dissolution of sulfur in ammonia has been known for more than 100 years [17]. The identification of the chemical species in these solutions was a matter of confusion until the identification of S4N and 83 , by Chivers and Lau [18] and Bernard et al. [19], using Raman spectroscopy. When considering the species formed in the dissolution process, it is quite remarkable that this dissolution is reversible sulfur is recovered after evaporation of ammonia. These solutions are strongly colored (blue), mainly due to the electronic absorption band of S4N at 580 nm. It must be mentioned that this dissolution is moderately fast at room temperature (but much slower than the dissolution of alkali metals) and that the rate is much slower when temperature decreases. It should also be mentioned that concentrated solutions of sulfur in liquid ammonia can be used as the solution at the positive electrode of a secondary battery. The solution at the negative electrode can be a solution of alkali metal in liquid ammonia [20], the electrodes being... 

As early as 1804, it was reported that sulfur dissolves in oleum to give brown, green or blue solutions [76]. As for solutions of sulfur in liquid ammonia, the nature of the colored species has been controversial. It was shown 30 years ago that sulfur can be oxidized with S2O6F2, AsFg, or SbFg in various solvents (H2SO4, HFSO3, HF, oleum) to polyatomic cations Sg +,... 

Benzobis-l,3-dithioles are converted by sulfur in liquid ammonia to benzobis-l,2,3-trithioles. This probably results from a nucleophilic attack at sulfur <88TL629l>. 

Polysulfide salts of several metals are known, and they can be prepared by the reaction of metals with sulfur in liquid ammonia or by dissolving sulfur in the molten metal sulfide. 

Lead(II) also forms numerous complexes that are mostly octahedral, although a phosphorodithioate, Pb(S2PPr2)2, is polymeric, with six Pb—S bonds and a stereo-chemically active lone pair. Interaction of the nitrate and NaSPh allows isolation of [Ph(As][Pb(SPh)3], which provides an example of trigonal pyramidal Pb11. A crystalline sulfide, PbS, can be prepared by reaction of elemental Pb and sulfur in liquid ammonia.164... 

There is a range of polysulfide dianions 8 that can be obtained by reaction of sulfur with simple sulfides, by high-temperature reaction of an alkali metal with sulfur, or by reaction of alkali metals with sulfur in liquid ammonia. Often, once formed, the anions are in equilibrium in solution, but individual anions can be complexed successfully. 8tructures of the free poly sulfide anions are shown in Figure 31. 

Aliphatic and aromatic dithiols react with elemental sulfur in liquid ammonia af 20 °C according to equation (87). ... 

Some important examples of the application of N NMR spectroscopy in S-N chemistry include (a) investigations of the (NSCOj 3NSC1 equilibrium in solution and (b) identification of the S-N species present in solutions of sulfur in liquid ammonia. The half-width of N NMR resonances is dependent on the symmetry of the atomic environment as well as other factors, such as solvent viscosity. The values may vary from ca. 10 Hz for solutions of NS2" AsFe in liquid SO2 to >1000 Hz in metal-S-N complexes. However, the chemical shift range for S-N compounds is ca. 800 ppm, so that useful information may frequently be obtained despite the broad lines. Liquid SO2 is a particularly good solvent for N NMR studies of cationic S-N species, while liquid ammonia is well suited to investigations of S-N anions/ ... 

Trithiane was synthesized in 38% yield from 1,3-propane thiol using elemental sulfur in liquid ammonia and proved to be very stable (Scheme 49) <1988BCJ1647>. Derivatives of 1,2,3-trithiane were obtained also as side products from other reactions but in each case were solidly identified, for example, 184 from the hydrosulfurization of penta-1,4-diene in DMF <1995J(P1)635> and 185 from the reaction between diethyl bis(/)-tolylsulfonyloxymethyl)-malonate and tetrasulfide ion <1988ACB620>. 

Trithiolobenzopentathiepins (33) and (34) were obtained by treatment of l,4-dialkyl-2,3,5,6-tetrabromobenzenes with elemental sulfur in liquid ammonia (Equation (23)), under these conditions o-diiodobenzene gave (35) with low yield <89TL2453>. 

Another route was proposed by Sato and co-workers. The synthesis of benzopentathiepins (35), (39), (52), and (53) was carried out by reactions of corresponding l,3-benzodithiole-2-thione or 1,2-benzenedithiol with elemental sulfur in liquid ammonia <86CL349, 88801647, 90YGK797). Per-hydrobenzopentathiepine (49) was obtained analogously (Scheme 33) <88801647). 

Sato et al., found that treatment of 2-(thiomethyl)benzene with elemental sulfur in liquid ammonia gave 6//-benzo[g ]-l,2,3,4,5-pentathiocine (186) (mp 61 °C) in 18% yield along with a seven-mem-bered ring polysulfide and the five-membered ring compound (187) (Scheme 17) <88BCJ1647>. Compound (187) could be converted to (186) by treatment with sulfur and liquid ammonia (Scheme 17) <90CL139>. 

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