Thiolato-Bridged Arene–Ruthenium Complexes: Synthesis, Molecular Structure, Reactivity, and Anticancer Activity of the Dinuclear Complexes [(arene)₂Ru₂ (SR)₂Cl₂]

Treatment of an arene–ruthenium dichloride dimer with thiols RSH to lead to cationic trithiolato complexes of the type [(arene) ₂Ru₂(SR)₃]⁺ was shown to proceed through the neutral thiolato complexes [(arene)₂Ru₂(SR)₂Cl₂], which have been isolated and characterized for arene = <i>p</i>-MeC₆H₄<i>i</i>Pr and R = CH₂Ph (<b>1</b>), CH₂CH₂Ph (<b>2</b>), CH₂C₆H₄-<i>p-t</i>Bu (<b>3</b>), and C₆H₁₁ (<b>4</b>). The single-crystal X-ray structure analysis of the <i>p-tert</i>-butylbenzyl derivative <b>3</b> reveals that the two ruthenium atoms are bridged by the two thiolato ligands without a metal–metal bond. The neutral dithiolato complexes[(arene)₂Ru₂(SR)₂Cl₂] (<b>1–3</b>) are intermediates in the formation of the cationic trithiolato complexes [(arene)₂Ru₂(SR)₃]⁺ (<b>5–7</b>). Of the new [(arene)₂Ru₂(SR)₂Cl₂] complexes, derivative 2 is highly cytotoxic against human ovarian cancer cells, with IC₅₀ values of 0.20 μM for the A2780 cell line and 0.31 for the cisplatin-resistant cell line A2780cisR.