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

The synthesis and X-ray structures of a half-sandwich Ru(II)p-cymene beta-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 [(eta(6)-p-cym)Ru(Ph(2)acac)Cl] (1), where Ph(2)acac=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 [(eta(6)-p-cym)Ru(Ph(2)acac)H(2)O]CF(3)SO(3).H(2)O.Et(2)O (4.H(2)O.Et(2)O), a possible activated species, possesses a comparatively short Ru-OH(2) bond. In the structure of [(eta(6)-p-cym)Ru(Ph(2)acac)9EtG-N7]CF(3)SO(3).2tol (5.2tol), where tol=toluene and 9EtG=9-ethylguanine, a comparatively long Ru-N7 bond is observed in addition to weak G CH8cdots, three dots, centeredO (Ph(2)acac) H-bonds. The crystal structure of [(eta(6)-p-cym)Ru(acac)9EtA-N7]PF(6) (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 N6Hcdots, three dots, centeredO(acac), which may contribute to the selectivity of {(eta(6)-p-cym)Ru(acac)}(+) towards adenine bases.