Highly cytotoxic diruthenium trithiolato complexes of the type [(?6-p-MeC6H4Pri)2Ru2(?2-SR)3]+: synthesis, characterization, molecular structure and in vitro anticancer activity

Cationic dinuclear p-cymene Ru complexes bridged by three thiophenolato ligands contg. various substituents mainly in meta and ortho positions, [(?6-p-MeC6H4Pri)2Ru2(?2-SR)3]+ (R = 3-C6H4Me: 1; R = 3-C6H4OMe: 2; R = 3-C6H4OEt: 3; R = 3-C6H4CF3: 4; R = 3-C6H4NH2: 5; R = 3-C6H4Cl: 6; R = 2-C6H4Me: 7; R = 2-C6H4OMe: 8; R = 2-C6H4Pri: 9; R = 2-C6H4CF3: 10; R = npt: 11 (npt = 2-naphthyl); R = mco: 12 (mco = 4-methylcoumarinyl); R = 3,5-C6H3Me2: 13; R = 3,5-C6H3(CF3)2: 14; R = 3,5-C6H3Cl2: 15; R = 3,4-C6H3(OMe)2: 16), were prepd. from the reaction of the neutral p-cymene diruthenium dichloride dimer, [(?6-p-MeC6H4Pri)2Ru2Cl4], with the corresponding thiophenol RSH. All cationic complexes were isolated as their chloride salts and fully characterized by spectroscopic and anal. methods. The mol. structures of 10 and 15 were solved by a single-crystal x-ray structure anal. of [10]Cl and [15]Cl, which show that the two Ru atoms adopt a pseudo-octahedral geometry without a metal-metal bond in accordance with the noble gas rule. All complexes are highly cytotoxic towards human ovarian cancer cells, the IC50 values being mostly in the nanomolar range. Complex 9 shows the highest cytotoxicity with an IC50 value of 0.03 ?M towards the A2780 cell line and the cisplatin-resistant mutant A2780cisR. The cytotoxicity of these complexes, which belong to the most active Ru anticancer compds. reported so far, can be correlated with the lipophilicity of the corresponding thiols. In comparison with the previous series, the positions of the substituents in the thiophenolato bridges are not as important as the nature of the substituents, alkyl substituents being the best ones in line with their lipophilic character. [on SciFinder(R)]