A series of compds. of general formula [Ru(.eta.6-p-cymene) (R2acac)(PTA)][X] (R2acac = Me2acac, tBu2acac, Ph2acac, Me2acac-Cl; PTA = 1,3,5-triaza-7-phosphaadamantane; X = BPh4, BF4), and the precursor to the Me2acac-Cl deriv. [Ru(.eta.6-p-cymene)(Me2acac-Cl)Cl], have been prepd. and characterised spectroscopically. Five of the compds. have also been characterised in the solid state by X-ray crystallog. The tetrafluoroborate salts are water-sol., quite resistant to hydrolysis, and have been evaluated for cytotoxicity against A549 lung carcinoma and A2780 human ovarian cancer cells. The compds. are cytotoxic towards the latter cell line, and relative activities are discussed in terms of hydrolysis (less important) and lipophilicity, which appears to exert the dominating influence.