3-DIMENSIONAL DELOCALIZATION IN TRIS(1,2-DITHIOLENES)

Tungsten tris(1,2-dithiolene) complexes 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 (H-1 NMR, UV/VIS, IR spectr al) closely related to each other through Hammett constant sigma(p)(+) , indicating extensive delocalization and conjugation. A comparative s tudy of complexes containing differently substituted dithiolenic rings showed that the electron delocalization is hot confined within each d ithiolenic 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 o f the effect of water and acid on the dimethylamine derivative. The ox idation number was assigned by recording the NMR spectra of the metal nuclei; the metals have effectively been stripped of their valence ele ctrons; 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 sigma and pi bonding.