Hartree Fock instabilities of sulfur‐nitrogen ring systems: S 2 N 2

The Hartree‐Fock instablities of S 2 N 2 are reported and compared with those of S 3 N   3 −and S 4 N   4 2+ . These unsaturated sulfur nitrogen planar rings are π electron rich and although the symmetry adapted HF solutions are singlet stable at the experimental bond lengths they become unstable with only a very modest increase in bond length. The broken symmetry solutions for S 2 N 3 , S 3 N   3 − , and S 4 N   4 2+are of planar C 2 v type with one of the nitrogens stripped of its π electrons, producing a π hole.