Sulfur diimide

Of particular interest is the reaction of 5,5-disubstituted sulfur diimides (188) with oxalyl chloride in dilute solution in the presence of triethylamine. The l,2,5-thiadiazole-3,5-dione (189) was formed in almost quantitative yield (72LA(759)107). 

The salt K2[SN2] is an important reagent for the preparation of other sulfur diimide derivatives when MesSiNSNSiMes is not sufficiently reactive. For example, both acyclic and cyclic arsenic(Iir) compounds, Bu2AsNSNAs Bu2 and BuAs(NSN)2As Bu, respectively, have been obtained in this way." ... 

Protonation of the anion [SN2] by acetic acid in diethyl ether produces the thermally unstable sulfur diimide S(NH)2. Like all sulfur diimides, the parent compound S(NH)2 can exist as three isomers (Scheme 5.5). Ab initio molecular orbital calculations indicate that the (cis,cis) configuration is somewhat more stable than the (cis,trans) isomer, while the (trans,trans) isomer is expected to possess considerably higher energy. The alternative syn,anti or E,Z nomenclatures may also be used to describe these isomers. The structures of organic derivatives S(NR)2 (R = alkyl, aryl) are discussed in Section 10.4.2. 

Salts of mono-alkylated or arylated sulfur diimide anion [RNSN] (R = aryl, Bu, SiMcs) are prepared by Si-N cleavage of RNSNSiMcs with [(Me2N)3S][Mc3SiF2]. ° ° These anions adopt cis configurations with very short terminal S-N bond lengths (1.44 - 1.49 A) indicative of a thiazylamide anion, [RNS N] (5.21). ... 

Thionyl imide, HNSO, is a thermally unstable gas, which polymerizes readily. It can be prepared by the reaction of thionyl chloride with ammonia in the gas phase. Organic derivatives RNSO have higher thermal stability, especially when R = Ar. The typical synthesis involves the reaction of a primary amine or, preferably, a silylated amine with thionyl chloride. A recent example is the preparation of FcNSO (Fc = ferrocenyl) shown in Eq. 9.8. In common with other thionylimines, FcNSO readily undergoes SO2 elimination in the presence of a base, e.g., KO Bu, to give the corresponding sulfur diimide FcNSNFc. 

The photolysis of 10.3a in pentane or the reaction of 10.3a with PPhs generate the corresponding sulfur diimide ArN=S=NAr (Ar = 2,4- Bu2-6-MeC6H2) as the major product, presumably via the intermediate formation of the thionitrosoarene." By contrast, thermolysis in arene solvents results in ring closure to give the 2,1-benzisothiazole 10.4 and the corresponding aniline."... 

Several methods for the preparation of unsymmetrical sulfur diimides RN=S=NR have been developed. One approach involves the addition of a catalytic amount of an alkali metal to a mixture of two symmetrical sulfur diimides, RN=S=NR and RT8i=S=NR. A second method makes use of alkali-metal derivatives of [RNSN] anions.Eor example, derivatives in which one of the substituents is a fluoroheteroaryl group can be prepared by the reaction of the anionic nucleophile [RN=S=N] with pentafluoropyridine. Sulfur diimides of the type RN=S=NH (R = 2,4,6- Bu3C6H2S) have also been prepared. "... 

Three different conformations are possible for monomeric chalcogen diimides (Eig. 10.1). Variable-temperature NMR spectra indicate that the cis,trans isomer of S(NR)2 is most stable in solution for small organic groups (R = Me, Bu). With bulkier organic substituents, small amounts of the trans,trans isomer exist in equilibrium with the cis,cis isomer. " The cis,cis isomer is observed in solutions of certain sulfur diimides with... 

In general, it was found that this process is strongly endothermic for sulfur diimides, approximately thermoneutral for selenium diimides and strongly exothermic for tellurium diimides, consistent with experimental observations. These differences can be attributed to the expected trend to lower r-bond energies for chalcogen-nitrogen (np-2p) r-bonds along the series S (n = 3), Se (n = 4) and Te (n = 5). 

Monomeric sulfur diimides have an extensive coordination chemistry as might be anticipated from the availability of three potential donor sites and two r-bonds. In addition, they are prone to fragmentation to produce thionitroso and, subsequently, sulfido and imido ligands. Under mild conditions with suitable coordinatively unsaturated metal... 

The most important fragmentation reactions of sulfur diimides occur with polynuclear metal carbonyls, e.g., M3(CO)i2 (M = Fe, in... 

Sulfur diimides may be reduced chemically (by alkali metals) or electrochemically to the corresponding radical anions [S(NR)2] , which... 

Scheme 10.5 Skeletal scrambling of sulfur diimide radical anions...

Redox reactions occur between sulfur diimides and reagents... 

Sulfur diimides react readily and quantitatively with organolithium reagents at the sulfur centre to produce lithium sulfmimidinates of the type Li[RS(NR )2] x- ° The lithium derivatives may be hydrolyzed by... 

The eight-membered rings 13.14 normally adopt boat conformations in the solid state with short S=N bond distances (1.51-1.52 A) that are typical of sulfur diimides. There are no transannular S S contacts. The sole exception is the antimony derivative BuSb(NSN)2Sb Bu, which is a planar eight-membered ring. 

The simplest chain compounds of the type RS NyR are the sulfur diimides RNSNR (Section 10.4) The other known thiazyl chains are summarized in Table 14.1. They can be conveniently classified as sulfur-rich, nitrogen-rich or even-chain species. 

The chemistry of the sulfur diimides (65) has been investigated in some detail, because such compounds might act as S—N or N—S—N transfer agents and thus allow access to novel heterocyclic systems. They are generally prepared by the action of sulfur tetrafluoride on primary amines.90 Some of their reactions parallel those of the /V-sulfinylamines— for example, the... 

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