Synthesis, characterization, and electrochemistry of diruthenium(III,II) and monoruthenium(III) complexes containing pyridyl-substituted 2-anilinopyridinate ligands

Reaction of the metal-metal bonded complex Ru(2)(O(2)CCH(3))(4)Cl with 2-anilino-4-methylpyridine leads to the (3,1) isomer of the diruthenium(III, II) complex Ru(2)(ap-4-Me)(4)Cl, 1 while the same reaction with 2-anilino-6-methylpyridine gives the monoruthenium(III) derivative Ru(ap-6-Me)(3), 2. Both compounds were examined as to their structural, electrochemical, and UV-visible properties, and the data were then compared to that previously reported for (4,0) Ru(2)(2-Meap)(4)Cl and other (3,1) isomers of Ru(2)(L)(4)Cl with similar anionic bridging ligands. ESR spectroscopy indicates that the monoruthenium derivative 2 contains low-spin Ru(III), and the presence of a single ruthenium atom is confirmed by an X-ray structure of the compound. The combined electrochemical and UV-vis spectroelectrochemical data indicate that the diruthenium complex 1 is easily converted to its Ru(2)(4+) and Ru(2)(6+) forms upon reduction or oxidation by one electron while the monoruthenium derivative 2 also undergoes metal-centered redox processes to give Ru(II) and Ru(IV) complexes under the same solution conditions. The reactivity of 1 with CO and CN(-) was also examined.