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.
A particularly stable derivative is di-t-butylsulfurdiimide.[1] 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.[2]
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.[3]
Sulfur diimides are electrophilic. They undergo Diels–Alder reactions with dienes.[1] 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]
4 LiNHBu-t + 2 S(NBu-t)2 → 2 Li2S(NBu-t)3 + 2 t-BuNH2