Organometallic ruthenium(II) complexes of general formula [RU(eta(6)-arene)Cl-2(NC5H4OOC-C5H4FeC5H5)], where arene = C6H6 (1), C6H5Me (2), p-(PrC6H4Me)-Pr-i (3), and C6Me6 (4), and of general formula [Ru(eta(6)-arene)Cl-2](2)(NC5H4OOC-C5H4FeC5H4-COOC5H4N), where arene = p-(PrC6H4Me)-Pr-i (5) and C6Me6 (6), have been synthesized and characterized, the molecular structures of these complexes being confirmed by single-crystal X-ray structure analysis of complex 4 as a representative example. The redox properties and in vitro anticancer activities of complexes 1-6 have been studied. All the compounds are moderately cytotoxic toward the A2780 and A2780cisR (cisplatin-resistant) human ovarian carcinoma cell lines. The diruthenium arene complexes 5 and 6 are about twice as active as their mononuclear analogues 3 and 4. Cyclic voltammetry revealed a good correlation of the Ru-II/Ru-III redox potentials of 1-4 and the number of alkyl substituents in the arene ligand.