Manifestation of sulfur-to-sulfur interaction in complexes of iron, ruthenium and osmium

The electron conducting ability of the -S-S- bridge was investigated using iron, ruthenium and osmium as metal centers and the bridging ligands 4,4'-d ithiodipyridine and bis(4-pyridine)sulfide. The observed back-bonding manif estations in mononuclear complexes, (evaluated through pK(a), MLCT and E-1: 2(o') data), the calculated comproportionation constant (K-c) for the homob inuclear species and the near-infrared (NIR) band characteristics of the ho mobinuclear and heterobinuclear mixed valence complexes consistently indica te a strong electron delocalization through the disulfide bridge. The avail able data strongly suggest a correlation between the conducting efficiency of the -S-S- bridge and the existence of a multiply bonded L...S...S...L co re. (C) 2000 Elsevier Science S.A. All rights reserved.