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 [Ti4L6](8-) clusters when reacted with Ti4+ starting materials, but instead gives dinuclear, triple-stranded complexes of type [Ti2L3](4-). The molecular structures of such complexes differ depending oil the size of the counterions employed. The formation of both meso complexes (Lambda,Delta or Delta,Lambda isomers) and of dinuclear triple-stranded helicates (Lambda,Lambda or Delta,Delta 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 unsymmetrical bis(beilzene-o-dithiol) ligand H-4-8 has been prepared. The unsymmetrical ligand can lead to four different stereoisomers when forming dinuclear triple-stranded complexes of type [Ti-2(8)(3)](4-), two of which have been observed in solution.