Sawhorse-type diruthenium tetracarbonyl complexes containing biologically relevant acids

The reaction between the biologically active acids probenecid (HO2CC12H18NO2S), indomethacin (HO2CC18H15ClNO2) and sulindac (HO2CC19H16FOS) with Ru3(CO)12, followed by addition of axial ligands (L), such as pyridine, triphenylphosphine, or 5-(4-pyridyl)-10,15,20-triphenylporphyrin, generates a series of stable diruthenium tetracarbonyl complexes of the formula Ru2(CO)4(μ2-η2-O2CC12H18NO2S)2L2, Ru2(CO)4(μ2-η2-O2CC18H15ClNO2)2L2 and Ru2(CO)4(μ2-η2-O2CC19H16FOS)2L2, respectively. The molecular structure of 1a · C6H6 was solved by single-crystal X-ray structure analysis and a typical diruthenium tetracarbonyl backbone bridged by the carboxylato ligands and two axial triphenylphosphine ligands was revealed. The benzene molecule sits between two probenecid units, and is involved in π-stacking interactions with the aromatic part of probenecid. Despite the presence of biologically relevant derivatives and carbonyl groups within the sawhorse-type dinuclear complexes, all systems show no cytotoxicity towards human cancer cells, presumably due to the high lipophilicity of these neutral complexes.