PREPARATION AND ELECTRONIC-STRUCTURE OF SUBSTITUTED AROMATIC DITHIOLENE COMPLEXES OF GOLD(III)

Ab initio calculations on the complex ion bis(benzene-1,2-dithiolato)a urate(III), I, have been performed and show that the two highest occup ied MO's have pi-character and correspond to the symmetric and antisym metric combination of the pure ligand HOMO's with only a very small co ntribution from gold orbitals. Both ligand and metal orbitals contribu te significantly to the LUMO which has sigma-character. A series of 10 derivatives of I have been prepared and isolated as tetra-n-butylammo nium salts. The electronic spectra of these species show two symmetry- forbidden transitions in good agreement with calculations. A spectroch emical series is proposed and related to the electron-releasing effici ency of the substituents. Comparison of the potentials for the reversi ble oxidation of the complexes (measured by cyclic voltammetry) with t he energy of the lowest lying electronic transition reveals a linear r elationship which is discussed in terms of the degree of charge transf er from ligands to metal. Improved synthesis of some of the ligands is reported.