Halogenido and carboxylato Ru(II) half-sandwich complexes of the general composition [Ru(η 6 -p-cym)(dpa)X]PF 6 (1-5) were prepared and thoroughly characterized with various techniques (e.g., mass spectrometry, NMR spectroscopy and X-ray analysis); dpa = 2,2 -dipyridylamine; p-cym = p-cymene; X = Cl − (for 1), Br − (for 2), I − (for 3), valproate(1−) (for 4) or 4-phenylbutyrate(1−) (for 5). A single-crystal X-ray analysis showed a pseudo-octahedral piano-stool geometry of [Ru(η 6 -p-cym)(dpa)I]PF 6 (3), with a η 6 -coordinated p-cymene, bidentate N-donor dpa ligand and iodido ligand coordinated to the Ru(II) atom. The results of the 1 H-NMR solution behaviour studies proved that the complexes 1-5 hydrolyse were in the mixture of solvents used (10% MeOD-d 4 /90% D 2 O). Complexes 1-5 were in vitro inactive against the A2780 human ovarian carcinoma cell line, up to the highest tested concentration (IC 50 > 100 µM).