Comparisons of MN 2 S 2 vs. bipyridine as redox-active ligands to manganese and rhenium in (L-L)M'(CO) 3 Cl complexes

The bipyridine ligand is renowned as a photo- and redox-active ligand in catalysis; the latter has been particularly explored in the complex Re(bipy)(CO) Cl for CO reduction. We ask whether a bidentate, redox-active MN S metallodithiolate ligand in heterobimetallic complexes of Mn and Re might similarly serve as a receptor and conduit of electrons. In order to assess the electrochemical features of such designed bimetallics, a series of complexes featuring redox active MN S metallodithiolates, with M = Ni , {Fe(NO)} , and {Co(NO)} , bound to M'(CO) X, where M' = Mn and Re, were synthesized and characterized using IR and EPR spectroscopies, X-ray diffraction, cyclic voltammetry, and density functional theory (DFT) computations. Butterfly type structures resulted from binding of the convergent lone pairs of the cis-sulfur atoms to the M'(CO) X unit. Bond distances and angles are similar across the M' metal series regardless of the ligand attached. Electrochemical characterizations of [MN S ·Re(CO) Cl] showed the redox potential of the Re is significantly altered by the identity of the metal in the N S pocket. DFT calculations proved useful to identify the roles played by the MN S ligands, upon reduction of the bimetallics, in altering the lability of the Re-Cl bond and the ensuing effect on the reduction of Re to Re .