Note. Evidence for through-space interactions between sulphur and nitrogen lone pairs in 2,2a,4,4a,6,6a-hexahydro-1,3,5-trithia-7-azacyclopenta[cd]-pentalene

Abstract

The X-ray crystal structure determination of the title compound has revealed a general flattening of the molecule with the nitrogen atom being pulled slightly into the plane defined by the three sulphur atoms. The crystals are rhombohedral, space group R3c, with a= 7.721 (2)Å, α= 105.14(2)°, and Z= 2. The structure was solved by direct methods and refined to a final R= 0.024 (R′= 0.041) for 649 unique reflections. Ab initio molecular orbital calculations show that the sulphur and nitrogen lone pairs interact to produce four highest occupied π-type molecular orbitals. The photoelectron spectrum shows only a single broad peak at –1.38 × 10^–18 J. This is consistent with the molecular orbital calculations which indicate that there should be three closely spaced transitions in this region from the highest occupied molecular orbitals.