Dinuclear ruthenium sawhorse-type complexes containing carboxylato bridges and ferrocenyl substituents: Synthesis and electrochemistry

The ferrocenyl-containing diruthenium complexes [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (Fc = ferrocenyl, fc = ferrocen-1,1′-diyl; <b>1</b>: L = NC₅H₄–COOC₆H₄–OC₁₀H₂₁, <b>2</b>: L = NC₅H₄–COOC₆H₄–OC₁₆H₃₃, <b>3</b>: L = NC₅H₄–OOC–fc–C₁₂H₂₅) and [Ru₂(CO)₄(μ₂-η²-OOC₆H₅)₂(NC₅H₄–OOC–fc–C₁₂H₂₅)₂] (<b>4</b>) have been synthesized from Ru₃(CO)₁₂, ferrocene carboxylic or benzoic acid and the corresponding pyridine derivative. The synthesis of the new pyridine derivative NC₅H₄–OOC–fc–C₁₂H₂₅ used for the preparation of <b>3</b> and <b>4</b> is also reported. Complexes <b>1–4</b> posses a so-called sawhorse structure consisting of the Ru₂(CO)₄ backbone and two bridging carboxylato ligands, while the coordination sphere around the ruthenium atoms is completed by the pyridine-derived ligands bonded in the axial positions. The electrochemical behavior of <b>1–4</b> and their known analogues [Ru₂(CO)₄(μ₂-η²-OOCFc)₂L₂] (<b>5</b>: L = NC₅H₅, <b>6</b>: L = P(C₆H₅)₃, <b>7</b>: L = NC₅H₄–OOCFc) has been studied by voltammetry on rotating disc electrode and by cyclic voltammetry.