REDOX CHEMISTRY AND SPECTROSCOPY OF TOLUENE-3,4-DITHIOL (TDTH2) AND OF ITS M(TDT)22-/- COMPLEXES WITH ZINC(II), COPPER(II), NICKEL(II), COBALT(II), IRON(II), AND MANGANESE(II) - FORMATION OF A STABLE DN-(.SR) BOND UPON OXIDATION BY ONE ELECTRON

In aprotic media, the anion of toluene-3,4-dithiol (TDTH2) is oxidized at -0.05 V vs. SCE to a disulfide dimer H2(TDT)2 by an irreversible one-electron process. The combination of its dianion (TDT2-) with divalent transition metals, M(II) (where M = Zn, Cu, Ni, Co, Fe, and Mn), in a two-to-one mole ratio yields stable complexes [MII(TDT)2]2-. Upon exposure to air these are rapidly oxidized to yield monoanionic species [M(TDT)2]-. The site of electron transfer for the oxidation of [M(TDT)2]2- to M(TDT)2- has been assigned to a bound sulfide group which spin pairs with an unpaired d electron of the transition metal to yield a stable covalent bond on the basis of the observed redox potentials, optical spectra, and magnetic properties. The monoanions, [M(TDT)2]-, display intense visible absorption bands that are assigned to the excitation of the MII .sbd. (.cntdot. TDT) bond. The structures for the [Cu(TDT)2] [Bu4N] and [Fe(TDT)2]2 [Bu4N]2 complexes have been determined by single-cystal X-ray diffractometry. The monomeric copper complex has a copper(II) center surrounded by an essentially iron complex is a dimer which contains the iron atom in a distorted square-pyramidal environment of sulfur atoms with average in-plane Fe.sbd.S distances of 2.221 (6) .ANG.. A sulfur atom from an ion across an inversion center occupies an axial position 2.513 (5) .ANG. from the iron atom.