Catalytic transfer hydrogenation and anticancer activity of arene-ruthenium compounds incorporating bi-dentate precursors

Ruthenium based organometallic compounds are presently a subject of great attention as anticancer drugs and appear to work reasonably well on tumor cells. We develop a series of mononuclear arene-ruthenium compounds incorporating N,O and N,N bidentate ligands, and their activity as anticancer drugs against human hormone-refractory metastatic prostate cancer (HRMPCs) cell lines are investigated. The ruthenium compounds also act as effective catalysts in the transfer hydrogenation of the -C=O- → -CH(OH)- system. Three types of ligands, namely, sodium glutamate, C₄H₃NH(2-CH₂NH^tBu), and C₄H₃NH(2-CH=NR) are separately coupled with [(η⁶-cymene)RuCl₂]₂ (1) (cymene = 4-isopropyltoluene) to synthesize five Ru-derivatives: [(η⁶-cymene)RuCl(κ²-N,O-OOCCHNH₂CH₂CH₂COOH)] (2), {(η⁶-cymene)RuCl[C₄H₃N(2-CH₂NH^tBu)]} (3), {(η⁶-cymene)RuCl[C₄H₃N(2-CH=NCH₂Ph)]} (4), {(η⁶-cymene)RuCl{C₄H₃N[2-CH=NCH₂(C₄H₇O)]}} (5) and {(η⁶-cymene)RuCl[C₄H₃N(2-CHⁿBuNHCH₂(C₄H₇O))]} (7). To the best of our knowledge, the aforementioned Ru compounds are not only characterized by ¹H and ¹³C NMR spectroscopy, but for the first time their structures have been established by single crystal X-ray diffractometry. Compound 4 influences a concentration-dependent apoptosis in PC-3 cells and initiates the conversion rate in transfer hydrogenation.