Intramolecular chalcogen-nitrogen interactions: molecular and electronic structures of geometrical isomers of the diazenes RSN=C(R')N=NC(R')=NSR

The structural isomers of the sulfur(II)-containing diazenes with PhSN=C(Ar)=NSPh (Ar = 2-BrC6H4) is characterized by an E,E,E geometry. X-ray analysis of the Z,E,Z isomers indicates the presence of a weak intramolecular sulfur-nitrogen bond which is stabilized by intramolecular E-N interactions. The interaction is characterized by back-donation between the phi lone pairs of the chalcogen and the phi*(N=N). Furthermore, the electron donation between the sigma(N) lone pairs and the sigma*(E-X) and sigma*(E-N) orbitals were also exhibited by the interaction.