1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester: A new bidentate ligand in arene ruthenium chemistry

1,1′-Ferrocene dicarboxylic acid pyridin-4-yl ester (<b>1</b>) is prepared from 1,1′-ferrocene dicarbonyl chloride and 4-hydroxypyridine. This new bidentate ferrocenoyl ligand reacts with the monocationic complex [(η⁶-<i>p</i>-cymene)₂Ru₂ (μ-OH)₃]⁺ to give the dicationic complex [(η⁶-<i>p</i>-cymene)₂Ru₂(μ-OH)₂(1,1′- (NC₅H₄–OOC)₂–Fc)]²⁺ (<b>2</b>) (Fc: C₅H₄–Fe–C₅H₄), isolated as a tetrafluoroborate salt. The single-crystal X-ray structure analysis of [<b>2</b>][BF₄] ₂ reveals the ferrocenoyl pyridine ligand <b>1</b> to act as μ₂-η² chelating ligand in the dinuclear complex, having replaced a μ₂-η¹-hydroxo ligand.