Sulfur diimide

Sulfur diimides are chemical compounds of the formula S(NR)2. Structurally, they are the diimine of sulfur dioxide. 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. 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. 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.

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 are electrophilic. They undergo Diels–Alder reactions with dienes. Organolithium reagents attack at the sulfur to give the corresponding nitrogen anion:
 * R'Li +  S(NR)2   →   R'S(NR)(NRLi)

The triimido analogues of sulfite can be generated by treating the sulfur diimides with a metal amide:
 * 4 LiNHBu-t +  2 S(NBu-t)2   →   2 Li2S(NBu-t)3  +  2 t-BuNH2