A mixed-ligand metal–metal bonded diruthenium complex having the formula Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl where ap is the anilinopyridinate anion was synthesized from the reaction of Ru2(O2CCH3)4Cl and H(2,4,6-(CH3)3ap), after which the isolated product was structurally, spectroscopically and electrochemically characterized. The crystal structure reveals an unusual arrangement of the bridging ligands around the dimetal unit where one ruthenium atom is coordinated to one anilino and two pyridyl nitrogen atoms while the other ruthenium atom is coordinated to one pyridyl and two anilino nitrogen atoms. To our knowledge, Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl is the only example of a mixed-ligand diruthenium complex of the type [Ru2L3(O2CCH3)]+, where L is an unsymmetrical anionic bridging ligand that has been structurally characterized with a “(2,1)” geometric conformation of the bridging ligands, all others being “(3,0)”. The initial Ru25+ compound in CH2Cl2 or CH3CN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) undergoes up to four one-electron redox processes involving the dimetal unit. The Ru25+/4+ and Ru25+/6+ processes were characterized under N2 using thin-layer UV-visible spectroelectrochemistry and this data is compared to UV-visible spectral changes obtained during similar electrode reactions for related diruthenium compounds having the formula Ru2L4Cl or Ru2L3(O2CCH3)Cl where L is an anionic bridging ligand. Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl was also examined by UV-visible and FTIR spectroelectrochemistry under a CO atmosphere and two singly reduced Ru24+ species, [Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO)Cl]− and Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO) were in situ generated for further characterization. The CO-bound complexes could be further reduced and exhibited additional reductions to their Ru23+ and Ru22+ oxidation states.

The electrochemistry and spectroelectrochemistry of a novel series of mixed-ligand diruthenium compounds were examined. The investigated compounds having the formula Ru2(CH3CO2)x(Fap)4−xCl where x = 1−3 and Fap is 2-(2-fluoroanilino)pyridinate anion were made from the reaction of Ru2(CH3CO2)4Cl with 2-(2-fluoroanilino)pyridine (HFap) in refluxing methanol. The previously characterized Ru2(Fap)4Cl as well as the three newly isolated compounds represented as Ru2(CH3CO2)(Fap)3Cl (1), Ru2(CH3CO2)2(Fap)2Cl (2), and Ru2(CH3CO2)3(Fap)Cl (3) possess three unpaired electrons with a Ru25+ dimetal core. Complexes 1 and 2 have well-defined Ru25+/4+ and Ru25+/6+ redox couples in CH2Cl2, but 3 exhibits a more complicated electrochemical behavior due to equilibria involving association or dissociation of the anionic chloride axial ligand on the initial and oxidized or reduced forms of the compound. The E1/2 values for the Ru25+/4+ and Ru25+/6+ processes vary linearly with the number of CH3CO2− bridging ligands on Ru2(CH3CO2)x(Fap)4−xCl and plots of reversible half-wave potentials vs the number of acetate groups follow linear free energy relationships with the largest substituent effect being observed for the oxidation. The major UV−visible band of the examined compounds in their neutral Ru25+ form is located between 550 and 800 nm in CH2Cl2 and also varies linearly with the number of CH3CO2− ligands on Ru2(CH3CO2)x(Fap)4−xCl. The electronic spectra of the singly oxidized and singly reduced forms of each diruthenium species were characterized by UV−visible spectroelectrochemistry in CH2Cl2.

A mixed-ligand metal–metal bonded diruthenium complex having the formula Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl where ap is the anilinopyridinate anion was synthesized from the reaction of Ru2(O2CCH3)4Cl and H(2,4,6-(CH3)3ap), after which the isolated product was structurally, spectroscopically and electrochemically characterized. The crystal structure reveals an unusual arrangement of the bridging ligands around the dimetal unit where one ruthenium atom is coordinated to one anilino and two pyridyl nitrogen atoms while the other ruthenium atom is coordinated to one pyridyl and two anilino nitrogen atoms. To our knowledge, Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl is the only example of a mixed-ligand diruthenium complex of the type [Ru2L3(O2CCH3)]+, where L is an unsymmetrical anionic bridging ligand that has been structurally characterized with a “(2,1)” geometric conformation of the bridging ligands, all others being “(3,0)”. The initial Ru25+ compound in CH2Cl2 or CH3CN containing 0.1 M tetra-n-butylammonium perchlorate (TBAP) undergoes up to four one-electron redox processes involving the dimetal unit. The Ru25+/4+ and Ru25+/6+ processes were characterized under N2 using thin-layer UV-visible spectroelectrochemistry and this data is compared to UV-visible spectral changes obtained during similar electrode reactions for related diruthenium compounds having the formula Ru2L4Cl or Ru2L3(O2CCH3)Cl where L is an anionic bridging ligand. Ru2(2,4,6-(CH3)3ap)3(O2CCH3)Cl was also examined by UV-visible and FTIR spectroelectrochemistry under a CO atmosphere and two singly reduced Ru24+ species, [Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO)Cl]− and Ru2(2,4,6-(CH3)3ap)3(O2CCH3)(CO) were in situ generated for further characterization. The CO-bound complexes could be further reduced and exhibited additional reductions to their Ru23+ and Ru22+ oxidation states.