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Sulfur diimides are chemical compounds of the formula S(NR)2. Structurally, they are the di
A particularly stable derivative is di- ''t''-butylsulfurdiimide.Kresze, G.; Wucherpfennig, W., "Organic synthesis with imides of sulfur dioxide", Angew. Chem. Int. Ed. Engl. 1967, volume 6, 149-167. It is prepared by reaction of ''tert''-butylamine with
imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bo ...
of sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
. The parent member, S(NH)2, is of only theoretical interest. Other derivatives where R is an organic group are stable and useful reagents.
Organic derivatives
A particularly stable derivative is di- ''t''-butylsulfurdiimide.Kresze, G.; Wucherpfennig, W., "Organic synthesis with imides of sulfur dioxide", Angew. Chem. Int. Ed. Engl. 1967, volume 6, 149-167. It is prepared by reaction of ''tert''-butylamine with sulfur dichloride
Sulfur dichloride is the chemical compound with the formula . This cherry-red liquid is the simplest sulfur chloride and one of the most common, and it is used as a precursor to organosulfur compounds. It is a highly corrosive and toxic substance, ...
to give the intermediate "S(N-''t''-Bu)", which decomposes at 60 °C to give the diimide. A second route to sulfur diimides involve treatment of sulfur tetrafluoride with amines. A third route involves transimidation of disulfonylsulfodiimide:
:S(NSO2Ph)2 + 2 RNH2 → S(NR)2 + 2 PhSO2NH2
''N'',''N-Bis(methoxycarbonyl)sulfur diimide (MeO2C-N=S=N-CO2Me) is obtained from methyl carbamate
Methyl carbamate (also called methylurethane, or urethylane) is an organic compound and the simplest ester of carbamic acid (H2NCO2H). It is a colourless solid.
Methyl carbamate is prepared by the reaction of methanol and urea:
:CO(NH2)2 + CH3O ...
.
Structure, bonding, reactions
These compounds are related to SO2. 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. Sulfur diimides areelectrophilic
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...
. They undergo Diels–Alder reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...
s with diene
In organic chemistry a diene ( ) (diolefin ( ) or alkadiene) is a covalent compound that contains two double bonds, usually among carbon atoms. They thus contain two alk''ene'' units, with the standard prefix ''di'' of systematic nomenclature. ...
s. Organolithium reagent
In organometallic chemistry, organolithium reagents are chemical compounds that contain carbon–lithium (C–Li) bonds. These reagents are important in organic synthesis, and are frequently used to transfer the organic group or the lithium atom ...
s attack at the sulfur to give the corresponding nitrogen anion:
:R'Li + S(NR)2 → R'S(NR)(NRLi)
The triimido analogues of sulfite
Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are wide ...
can be generated by treating the sulfur diimides with a metal amide Metal amides (systematic name metal azanides) are a class of coordination compounds composed of a metal center with amide ligands of the form NR2−. Amide ligands have two electron pairs available for bonding. In principle, they can be terminal or ...
:Fleischer, R.; Stalke, D., "A new route to sulfur polyimido anions S(NR)nm-: reactivity and coordination behavior", Coord. Chem. Rev. 1998, 176, 431-450. {{doi, 10.1016/S0010-8545(98)00130-1
::4 LiNHBu-t + 2 S(NBu-t)2 → 2 Li2S(NBu-t)3 + 2 t-BuNH2
See also
*Carbodiimide
In organic chemistry, a carbodiimide (systematic IUPAC name: methanediimine) is a functional group with the formula RN=C=NR. They are exclusively synthetic. A well known carbodiimide is dicyclohexylcarbodiimide, which is used in peptide synthesis. ...
- the carbon analogue
* Disulfur dinitride
Disulfur dinitride is the chemical compound with the formula .
Preparation and reactions
Passing gaseous over silver metal wool at 250–300 °C at low pressure (1mm Hg) yields cyclic . The silver reacts with the sulfur produced by the the ...
* Bis(trimethylsilyl)sulfur diimide
References