Mono-and binuclear arene–ruthenium(II) complexes with imidazole-containing ligands were prepared by the reaction of the ligands (L ¹ = bis(imidazole-1-yl)methane; ImH = 1H-Imidazole; BImH = 1H-Benzimidazole) with [(p-cym)Ru(µ-Cl) ₂ ] ₂ dimers. When bis(imidazole-1-yl)methane re-acted with [(p-cym)Ru(µ-Cl) ₂ ] ₂ in methanol, a binuclear complex of the type [Ru ₂ (L ¹ ) ₂ (p-cym) ₂Cl ₂ ]Cl ₂ (2) with cyclic structure was synthesized, whereas by using acetonitrile as a solvent under the same reaction conditions, an unexpected C–N bond cleavage was observed, and a complex of formula [Ru(ImH) ₂ (p-cym)Cl]Cl (1) with coordinated imidazole molecules was obtained. Another type of arene–ruthenium complex [Ru(BImH)(p-cym)Cl ₂ ] (3) was obtained by the reaction of benzimidazole and [(p-cym)Ru(µ-Cl) ₂ ] ₂ . All compounds were characterized by spectral (FT-IR, NMR ¹H, ¹³C) and single-crystal X-ray diffraction methods; their catalytic activity in transfer hydrogenation and the cytotoxicity against MCF-7 and HepG2 cells were evaluated.