These compounds are related to SO.  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:
:RLi  +  S(NR)   →   RS(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 LiS(NBu-t)  +  2 t-BuNH