Cyclic sulfur imides

The reaction of S2C12 with gaseous ammonia in DMF at ca. -10 °C, followed by hydrolysis with cold dilute hydrochloric acid, is a standard preparation of these cyclic sulfur imides.199 The reaction of sodium azide with elemental sulfur in (Me2N)3PO is an excellent source of S7NH. The tetraimide 69 is prepared by reduction of S4N4 with methanolic SnCl2.2H20. 

The vibrational assignments and force constants have been determined from the IR and Raman spectra of S7NH, S415N4H4 and S415N4D4. The 1H and 15N NMR chemical shifts of all the cyclic sulfur imides have been determined by inverse detection methods.202 

Deprotonation of S7NF1 produces the thermally unstable, yellow [S7N] anion, which decomposes to the deep blue [S4N] anion.69 The oxidation of S7NH with trifluoroperoxyacetic acid yields S7NH(0), while oxidation with SbCl5 in liquid sulfur dioxide generates the [NS2]+ cation. 

The interaction of cyclic sulfur imides with metal centres involves adduct formation or oxidative addition.106 Examples of the former include the formation of [M(S4N4H4)(CO)5] (70, M=Cr, W) and (S4N4H4)2 AgC104. By contrast, the reaction of 69 with [Pt(PPh3)4] gives pt(PPh3)2(S2N2)]. Monomeric 

Sulfur imides with a single NR functionality, S5NR, SgNR (R=Oct), SgNH and S9NH are obtained by the metathesis reaction between the / is (c y c l o pern a d i c n y l) t i t ani um complexes 71-73 and the appropriate di-chlorosulfane.206,207 

The six-membered rings 1,4-S4(NR)2 (R=Et, Bz, Cy, CH2CH2Ph) are prepared from the reactions of the appropriate primary amine with S2CI2 in diethyl 

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When the reaction of S2CI2 with ammonia is carried out in a polar solvent, e.g., DMF, the hydrolysis of the reaction mixture with aqueous HCl produces a mixture of the cyclic sulfur imides S7NH, 1,3-, 1,4- and 1,5-S6(NH)2 and 1,3,5- and 1,3,6-S5(NH)3, which can be separated by chromatography on silica gel using CS2 as eluant (Section 6.2.1). °... 

Fig. 3.1 NMR chemical shifts for NH groups in cyclic sulfur imides...

Mass spectrometry played an important role in the recent characterization of small cyclic sulfur imides that are formally derived from the unstable cyclic sulfur allotropes Se and S7 by the replacement of one sulfur atom by an NR group. The compounds SsNOct and SeNOct (Section 6.2.2), which are yellow oils, exhibit molecular ions of medium intensity in their mass spectra. ... 

The formal replacement of a sulfur atom in cyclo-S generates S7NH (6.1), the first member of a series of cyclic sulfur imides that includes the three diimides 1,3-, 1,4-, and 1,5-S6(NH)2 (6.2-6.4), two triimides 1,3,5-and 1,3,6-S5(NH)3, and S4N4H4 (6.5). Isomers of these ring systems containing adjacent NH groups are not known. 

The cyclic sulfur imides readily undergo condensation reactions in the presence of a base, e.g., pyridine. For example, the reaction of S7NH with sulfur halides, S Cla or SOCI2, produces the series (S7N)2Sx (x = 1, 2, 3, 5), or (S7N)2S0, respectively. The bicyclic compound S11N2 (6.6) is obtained by treatment of 1,3-S6(NH)2 with The reaction... 

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. 

Role of Sulfur-Nitrogen Anions in the Synthesis of Cyclic Sulfur Imides... 

The cyclic sulfur imides S NH and 1,3-, 1,4-, and l,5-S(j(NH)2 are obtained by acid hydrolysis of the deep blue intermediate formed from the reaction of SjClj with ammonia in polar solvents, e.g. DMF or by the reaction of sodium azide with elemental sulfur in HMPA The blue chromophore formed in both these reactions is S4N and it has therefore been suggested that this anion is involved in equilibria with cyclic sulfur-nitrogen anions which are the precursors of the imides... 

Cyclic sulfur imides are molecules in which one (or more) of the sulfur atoms in a cyclic sulfur allotrope is replaced by an NR (R = H, alkyl) group (see 2.1-2.4... 

The standard preparation of these cyclic sulfur imides, with the exception of cyclo-S4N4H4, involves the reaction of S2CI2 with gaseous ammonia in a polar solvent, e.g. DMF, at —10°C followed by hydrolysis with cold, dilute HCl... 

Two types of behaviour are observed in the interaction of cyclic sulfur imides with metal centres (a) adduct formation and (b) oxidative addition. The formation of S -bonded adducts, e.g. (S4N4H4)M(CO)5 (M = Cr, W) and the sandwich complex (S4N4H4)y AgC104 (see Figure 7.2), is discussed in Section 7.1.1. Oxidative addition involving insertion of the metal into an S-S bond of the cyclic sulfur imide SyNR (R = H, Me) occurs with Cp2Ti(CO)2, as illustrated in Scheme 12.4." ... 

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