Dinuclear ruthenium sawhorse-type complexes containing bridging ligands with ferrocenyl substituents in endo/endo, endo/exo and exo/exo orientations

The dinuclear ruthenium complexes Ru2(CO)4(OOCC5H4FeC5H5)2L2 (L = NC5H5: 1, L = PPh3: 2) have been synthesized from Ru3(CO)12, ferrocene carboxylic acid and pyridine or triphenylphosphine, respectively. The single-crystal X-ray structure analysis reveals for 1 and 2 a Ru2(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 Ru2(CO)4(OOCC5H4FeC5H5)2(NC5H4OOCC5H4FeC5H5)2 (4) was obtained, the single crystal X-ray structure analysis showing an exo/exo orientation of the two carboxylato bridges in the solid state. The endo/endo orientation is found in the solid-state structure of Ru2(CO)4(HNOCC5H4FeC5H5)2(PPh3)2 (5), the two OCNH bridges being transoïd with respect to each other; this complex is accessible from Ru3(CO)12, ferrocenamide and triphenylphosphine.