The dinuclear ruthenium complexes Ru-2(CO)(4)(OOCC5H4FeC5H5)(2)L-2 (L = NC5H5: 1, L = PPh3: 2) have been synthesized from Ru-3(CO)(12), ferrocene carboxylic acid and pyridine or triphenylphosphine, respectively. The single-crystal X-ray structure analysis reveals for 1 and 2 a Ru-2(CO)4 sawhorse backbone with the two ferrocenyl substituents of the two carboxylato bridges being endo/exo with respect to each other in the solid state. With the new pyridine derivative NC5H4OOCC5H4FeC5H5 (4-ferrocenoyl pyridine) (3) as axial ligand, the complex Ru-2(CO)(4)(OOCC5H4FeC5H5)(2)(NC5H4OOCC5H4FeC5H5)(2) (4) was obtained, the single crystal X-ray structure analysis showing an exo1exo orientation of the two carboxylato bridges in the solid state. The endo/endo orientation is found in the solid-state structure of Ru-2(CO)(4)(HNOCC5H4FeC5H5)(2)(PPh3)(2) (5), the two OCNH bridges being transoid with respect to each other; this complex is accessible from Ru3(CO)(12), ferrocenamide and triphenylphosphine. (c) 2005 Elsevier B.V. All rights reserved.