A series of cationic dinuclear p-cymene ruthenium trithiophenolato complexes of the type [(g 6-p-MeC 6 H 4 Pr i) 2 Ru 2 (SC 6 H 4-p-X) 3 ] ? (1 X is H, 2 X is Me, 3 X is Ph, 4 X is Br, 5 X is OH, 6 X is NO 2 , 7 X is OMe, 8 X is CF 3 , 9 X is F, 10 X is Pr i , 11 X is Bu t) have been synthesized from the reaction of [(g 6-p-MeC 6 H 4 Pr i)-RuCl 2 ] 2 with the corresponding thiol, isolated as the chloride salts, and further studied for their electrochemical properties, cytotoxicity towards human ovarian cancer cells, and catalytic activity for glutathione (GSH) oxidation. Complex 1 was also compared with the benzene and hexamethylbenzene analogues [(g 6-C 6 H 6) 2 Ru 2 (SC 6 H 5) 3 ] ? (12) and [(g 6-C 6 Me 6) 2 Ru 2 (SC 6 H 5) 3 ] ? (13). The most active compound [11]Cl was structurally studied by single-crystal X-ray diffraction analysis. The concentrations corresponding to 50 % inhibition of cancer cell growth (IC 50 values) in the A2780 and A2780cisR cell lines of these complexes except for 6 were in the submicromolar range, complex 11 showing an IC 50 value of 0.03 lM in both cell lines. The high in vitro anticancer activity of these complexes may be at least partially due to their catalytic potential for the oxidation of GSH, although there is no clear correlation between the IC 50 values and the turnover frequencies at about 50 % conversion. However, the cytotoxicity is tentatively correlated to the physicochemical properties of the compounds determined by the electronic influence of the substituents X (Hammett constants r p) and the lipophilicity of the thiols p-XC 6 H 4 SH (calculated log P parameters).

Keywords: Ruthenium / Arene ligands / Thiolato bridges / CytotoxicityTreatment of an arene-ruthenium dichloride dimer with thiols RSH to lead to cationic trithiolato complexes of the type [(arene) 2 Ru 2 (SR) 3 ] + was shown to proceed through the neutral thiolato complexes [(arene) 2 Ru 2 (SR) 2 Cl 2 ], which have been isolated and characterized for arene = p-MeC 6 H 4 iPr and R = CH 2 Ph (1), CH 2 CH 2 Ph (2), CH 2 C 6 H 4 -p-tBu (3), and C 6 H 11 (4). The single-crystal X-ray structure analysis of the p-tert-butylbenzyl derivative 3 reveals that the two ruthe-