{{Chembox |ImageFile=Sulfur diimide.png |IUPACName=diimino-λ<sup>4</sup>-sulfane |OtherNames = 2λ<sup>4</sup>-Diazathia-1,2-diene |Section1={{Chembox Identifiers |CASNo = 21918-40-1 | CASNo_Ref = {{Cascite|changed|???}} |ChemSpiderID = 298618 |PubChem = 336934 |StdInChI=1S/H2N2S/c1-3-2/h1-2H |StdInChIKey = HQFYRKYAKZRZCJ-UHFFFAOYSA-N |SMILES = N=S=N }} |Section2={{Chembox Properties |H=2|N=2|S=1 }} }} '''Sulfur diimides''' are chemical compounds of the formula S(NR)<sub>2</sub>. Structurally, they are the diimine of sulfur dioxide. The parent member, S(NH)<sub>2</sub>, is of only theoretical interest. Other derivatives where R is an organic group are stable and useful reagents.
==Organic derivatives== thumb|left|upright=0.85|Structure of S(NBu-t)<sub>2</sub>. A particularly stable derivative is di-''t''-butyl{{zwj}}sulfurdiimide.<ref name= Kresze>Kresze, G.; Wucherpfennig, W., "Organic synthesis with imides of sulfur dioxide", Angew. Chem. Int. Ed. Engl. 1967, volume 6, 149-167. {{doi|10.1002/anie.196701491}}</ref>{{failed verification|date=April 2026}} It is prepared by reaction of ''tert''-butylamine with sulfur dichloride to give the intermediate "S(N-''t''-Bu)", which decomposes at 60 °C to give the diimide.{{cn|date=April 2026}} Contrariwise, the trimethylsilyl derivative S(NSiMe<sub>3</sub>)<sub>2</sub> is prepared from lithium hexamethyldisilazane and thionyl chloride.<ref>{{cite thesis|p=26|institution=University of Calgary|url=https://ucalgary.scholaris.ca/server/api/core/bitstreams/87cfc535-9c7d-45c2-a6d1-dd9aeb71c11b/content|title=Synthesis and Spectroscopic Characterization of Acyclic Sulphur-Nitrogen and Sulphur-Nitrogen-Oxygen Anions|first=Kenneth J.|last=Schmidt|type=PhD|date=March 1990}}</ref>
However, most sulfur diimides are not produced from such elimination reactions. Typically, sulfur diimides arise from treatment of sulfur tetrafluoride with amines, or from transamidation reactions. The latter typically requires amide reactants that are less basic than the products,<ref name=Sulf>{{cite book|title=Sulfur in Organic and Inorganic Chemistry|volume=1|editor-first=Alexander|editor-last=Senning|year=1971|publisher=Marcel Dekker|location=New York|lccn=70-154612|isbn=0-8247-1615-9|first=H. W.|last=Roesky|chapter=The Sulfur–Nitrogen Bond|pages=24–25,32}}</ref> as with disulfonylsulfodiimide... :S(NSO<sub>2</sub>Ph)<sub>2</sub> + 2 RNH<sub>2</sub> → S(NR)<sub>2</sub> + 2 PhSO<sub>2</sub>NH<sub>2</sub> ...or with ''N'',''N'''-Bis(methoxycarbonyl)sulfur diimide (MeO<sub>2</sub>C-N=S=N-CO<sub>2</sub>Me) from methyl carbamate.<ref>{{cite journal|doi=10.15227/orgsyn.065.0159|title=Allylcarbamates by the Aza-Ene Reaction: Methyl ''N''-(2-Methyl-2-Butenyl)Carbamate|journal=Organic Syntheses|volume=65|pages=159|year=1987|first1=Günter|last1=Kresze|first2=Hans|last2=Braxmeier|first3=Heribert|last3=Münsterer}}</ref> Alternatively, the presence of a strong base to absorb the released SO<sub>2</sub> can drive transamidation from sulfinylamines.<ref name=Sulf/>
==Structure, bonding, reactions== These compounds are related to SO<sub>2</sub>. They have planar C–N=S=N–C cores with bent C–N=S and N=S=N geometries, and various combinations of ''E'' and ''Z'' isomers are observed for the two N=S bonds.<ref>{{cite journal |journal= Journal of Fluorine Chemistry |volume= 115 |issue= 2 |year= 2002 |pages= 165–168 |title= The first ''N''-alkyl-''{{prime|N}}''-polyfluorohetaryl sulfur diimide |first1= Enno |last1= Lork |first2= Ruëdiger |last2= Mews |first3= Makhmut M. |last3= Shakirov |first4= Paul G. |last4= Watson |first5= Andrey V. |last5= Zibarev |doi= 10.1016/S0022-1139(02)00047-7 }}</ref>
Sulfur diimides are electrophilic.<ref name= Kresze/> The triimido analogues of sulfite can be generated by treating the sulfur diimides with a metal amide:<ref>Fleischer, R.; Stalke, D., "A new route to sulfur polyimido anions S(NR)<sub>n</sub><sup>m-</sup>: reactivity and coordination behavior", Coord. Chem. Rev. 1998, 176, 431-450. {{doi|10.1016/S0010-8545(98)00130-1}}</ref> :4 LiNHBu-t + 2 S(NBu-t)<sub>2</sub> → 2 Li<sub>2</sub>S(NBu-t)<sub>3</sub> + 2 t-BuNH<sub>2</sub> Organolithium reagents attack at the sulfur to give the corresponding nitrogen anion: :R'Li + S(NR)<sub>2</sub> → R'S(NR)(NRLi) The addition is accompanied by "a colour change which makes the diimines useful as titrants for Grignard reagents".<ref>{{cite journal|doi=10.1016/S0277-5387(00)84411-3|p=618|journal=Polyhedron|volume=5|issue=3|year=1986|location=Great Britain|publisher=Pergamon|title=The preparation and structure of complexes containing simple sulphur-nitrogen ligands|first1=Paul F.|last1=Kelly|first2=J. Derek|last2=Woollins|id=Report #14}}</ref>
Sulfur diimides undergo Diels–Alder reactions with dienes.<ref name= Kresze/>
Fluorine gas oxidizes them to difluorosulfur diimides:<ref name=Sulf/> :RNSN{{prime|R}} + F<sub>2</sub> → RNS(F)<sub>2</sub>N{{prime|R}}
==See also== * Carbodiimide - the carbon analogue * Disulfur dinitride * Bis(trimethylsilyl)sulfur diimide
==References== <references />
Category:Sulfur(IV) compounds Category:Functional groups Category:Heteroallenes