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)H2O]CF3SO3 center dot H2O center dot Et2O (4 center dot H2O center dot Et2O), a possible activated species, possesses a comparatively short Ru-OH2 bond. In the structure of [(eta(6) -p-cym)Ru(Ph(2)acac)9EtA-N7]CF3SO3 center dot 2tol (5 center dot 2tol), where tol = toluene and 9EtG = 9-ethylguanine, a comparatively long Ru-N7 bond is observed in addition to weak G CH8 center dot center dot center dot O (Ph(2)acac) H-bonds. The crystal structure of [(eta(6) -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 center dot center dot center dot O(acac), which may contribute to the selectivity of {(eta(6) -p-cym)Ru(acac)}(+) towards adenine bases. (c) 2007 Elsevier Inc. All rights reserved.