Chlorido-, aqua-, 9-ethylguanine- and 9-ethyladenine-adducts of cytotoxic ruthenium arene complexes containing O,O-chelating ligands

Abstract

The synthesis and X-ray structures of a half-sandwich RuIIp-cymene β-diketonato complex as chlorido-, aqua-, 9-ethylguanine- and 9-ethyladenine-adducts are reported. Structural features which contribute to stabilisation of adducts through non-covalent, weak interactions are discussed. The X-ray crystal structure of the cytotoxic complex [(η6-p-cym)Ru(Ph2acac)Cl] (1), where Ph2acac=1,3-diphenyl-1,3-propanedionate and p-cym=para-cymene, shows that the phenyl rings of the acac-type ligand form a hydrophobic face, conferring lipophilic character on the complex. The structure of the aqua adduct [(η6-p-cym)Ru(Ph2acac)H2O]CF3SO3·H2O·Et2O (4·H2O·Et2O), a possible activated species, possesses a comparatively short Ru–OH2 bond. In the structure of [(η6-p-cym)Ru(Ph2acac)9EtG-N7]CF3SO3·2tol (5·2tol), where tol=toluene and 9EtG=9-ethylguanine, a comparatively long Ru–N7 bond is observed in addition to weak G CH8⋯O (Ph2acac) H-bonds. The crystal structure of [(η6-p-cym)Ru(acac)9EtA-N7]PF6 (6), where acac=acetylacetonate and 9EtA=9-ethyladenine, a rare example of a ruthenium complex containing monodentate adenine, shows a strong H-bonding interaction between N6H⋯O(acac), which may contribute to the selectivity of {(η6-p-cym)Ru(acac)}+ towards adenine bases.