Organometallic cis-Dichlorido Ruthenium(II) Ammine Complexes

Bifunctional neutral half-sandwich Ru(II) complexes of the type [(η(6)-arene)Ru(NH(3))Cl(2)] where arene is p-cym (1) or bip (2) were synthesised by the reaction of N,N-dimethylbenzylamine (dmba), NH(4)PF(6) and the corresponding Ru(II) arene dimer, and were fully characterised. X-ray crystallographic studies of [(η(6)-p-cym)Ru(NH(3))Cl(2)]·{(dmba–H)(PF(6))} (1a) and [(η(6)-bip)Ru(NH(3))Cl(2)] (2) show extensive H-bond interactions in the solid state, mainly involving the NH(3) and the Cl ligands, as well as weak aromatic stacking interactions. The half-lives for the sequential hydrolysis of 1 and 2 determined by UV/Vis spectroscopy at 310 K ranged from a few minutes for the first aquation to ca. 45 min for the second aquation; the diaqua adducts were the predominant species at equilibrium. Arene loss during the aquation of complex 2 was observed. Upon hydrolysis, both complexes readily formed mono- and di-9-ethylguanine (9-EtG) adducts in aqueous solution at 310 K. The reaction reached equilibrium after ca. 1.8 h in the case of complex 1 and was slower but more complete for complex 2 (before the onset of arene loss at ca. 2.7 h). Complexes 1 and 2 were not cytotoxic towards A2780 human ovarian cancer cells up to the maximum concentration tested (100 μM).