Synthesis, structure and electrochemistry of cationic diruthenium complexes of the type [(N∩N)₂Ru₂ (CO)₂ (μ-CO)₂(μ-OOCFc)]⁺ containing a ferrocenecarboxylato bridge and two chelating aromatic diimine ligands

The dinuclear bis(ferrocenecarboxylato) complex Ru₂ (CO)₄ (μ-OOCFc)₂ (py)₂ (Fc = ferrocenyl, py = pyridine) was found to react with aromatic diimines (2,2′-dipyridyl, 4,4′-dimethyl-2,2′-dipyridyl, 1,10-phenanthroline, 5-nitro-1,10-phenanthroline, and 5-amino-1,10-phenanthroline) in methanol to give the cationic diruthenium complexes [(N∩N)₂Ru₂ (CO)₂ (μ-CO)₂(μ-OOCFc)]⁺ (<b>1</b>: N∩N = 2,2′-dipyridyl, <b>2</b>: N∩N = 4,4′-dimethyl-2,2′-dipyridyl, <b>3</b>: N∩N = 1,10-phenanthroline, <b>4</b>: N∩N = 5-nitro-1,10-phenanthroline, <b>5</b>: N∩N = 5-amino-1,10-phenanthroline), which have been isolated as the hexafluorophosphate salts. The molecular structure of <b>3</b>, solved by single-crystal X-ray analysis of the tetraphenylborate salt [<b>3</b>][BPh₄], shows a diruthenium backbone bridged by two carbonyl and by one ferrocenecarboxylato ligand, the two 1,10-phenanthroline ligands being in the axial positions. Cyclic voltammetry in dichloromethane reveals for all compounds two successive oxidations due to ferrocene/ferrocenium redox couple and oxidation of the diruthenium core.