Metallosupramolecular complexes derived from bis(benzene-o-dithiol) Ligands

Contrary to its catechol analogue, the 1,5-naphthalenediamido-bridged bis(benzene-o-dithiol) ligand H ₄-3 does not yield [Ti ₄L ₆] ^8- clusters when reacted with Ti ⁴⁺ starting materials, but instead gives diouclear, triple-stranded complexes of type [Ti ₂L ₃] ^4-. The molecular structures of such complexes differ depending on the size of the counterions employed. The formation of both meso complexes (δ,δ or δ,δ isomers) and of dinuclear triple-stranded helicates (δ,δ or δ,δ isomers) was observed. Molecular-modeling calculations show energetically close minima for the meso complex and the corresponding helicate. In spite of the structural differences in the solid state, proton NMR spectra reveal C ₃ symmetry for all three complex anions. Metal-donor interactions mainly dictate the coordination behavior, whereas the topology of the ligand has less influence. In addition, the dinuclear complex [Ti ₂(8) ₃] ^4- with the unsymmet-rical bis(benzene-o-dithiol) ligand H ₄-8 has been prepared. The unsymmetrical ligand can lead to four different stereo-isomers when forming dinuclear triple-stranded complexes of type [Ti ₂(8) ₃] ^4-, two of which have been observed in solution.