Metal/Metal Redox Isomerism Governed by Configuration

A pair of diastereomeric dinuclear complexes, [Tp '(CO)BrW{mu-eta(2)-C,C '-kappa(2)-S,P-C-2(PPh2)S}Ru(eta(5)-C5H5)(PPh3)], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side-on carbon P,S-chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like-isomer is oxidized at W while the unlike-isomer is oxidized at Ru, which is proven by IR, NIR and EPR-spectroscopy supported by spectro-electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step. Finally, the tipping point could be realized in the unlike isomer of the electronically tuned thiophenolate congener [Tp '(CO)(PhS)W{mu-eta(2)-C,C '-kappa(2)-S,P-C-2(PPh2)S}Ru(eta(5)-C5H5)-(PPh3)], in which valence trapped W-III/Ru-II and W-II/Ru-III cationic species are at equilibrium.