Synthesis, X-ray diffraction structure, spectroscopic properties and antiproliferative activity of a novel ruthenium complex with constitutional similarity to cisplatin

The light-protected reaction of [(eta(6)p-cymene)(RuCl2)-Cl-II](2) with 1-(2-hydroxyethyl)piperazine in dry methanol, followed by addition of excess NH4PF6, afforded the complex [(eta(6)-p-cymene)Ru-II(NH3)(2)Cl]-(PF6) (1) in 47% yield. Attempts to use the same protocol for the synthesis of [(eta(6)-pcymene)Os-II(NH3)(2)-Cl](PF6) led to the isolation of the binuclear triply methoxido-bridged arene-osmium compound [{(eta(6)-p-cymene)Os}(2)(mu-OCH3)(3)](PF6) (3). Both compounds were characterised by X-ray crystallography and H-1 NMR spectroscopy, and the ruthenium complex also by spectroscopic techniques (IR and UV-vis spectroscopies). The antiproliferative activity of complex 1 in vitro was studied in A549 (non-small cell lung carcinoma), CH1 (ovarian carcinoma), and SW480 (colon carcinoma) cells and compared to that of [(eta(6) p-cymene)Ru-II(en)Cl](PF6) (2). In contrast to the latter compound, 1 is only modestly cytotoxic in all three cell lines (IC50: 293-542 mu M), probably due to the instability of the diammine ruthenium complex in aqueous solution.