Three-dimensional delocalization in tris(1,2-dithiolenes)

Abstract

Tungsten tris(1,2-dithiolene) complexes [W(S ₂ C ₂ R ¹ R ⁶ )(S ₂ C ₂ R ² R ⁵ )(S ₂ C ₂ R ³ R ⁴ )] (R ^4,5,6 = H or Ph; R ^1,2,3 = para-substituted Ph), have been found to exhibit properties ( ¹ H NMR, UV/VIS, IR spectral) closely related to each other through Hammett constant σ _p ⁺ , indicating extensive delocalization and conjugation. A comparative study of complexes containing differently substituted dithiolenic rings showed that the electron delocalization is not confined within each dithiolenic ring separately, but involves all of them, i.e. it is three dimensional. This is further supported by a NMR and/or UV/VIS study of the effect of water and acid on the dimethylamine derivative. The oxidation number was assigned by recording the NMR spectra of the metal nuclei; the metals have effectively been stripped of their valence electrons; which are placed on the ligands. The non-planar ‘aromaticity' of the dithiolenes differs from the familiar flat organic aromaticity since it involves mixing of σ and π bonding.