Platinum(II) complexes containing ferrocene-derived phosphonate ligands; synthesis, structural characterisation and antitumour activity

Platinum ferrocenyl–phosphonate complexes, containing four-membered PtOP(O)O rings, have been synthesised by the reactions of cis-[PtCl2(PPh3)2] with the ferrocene-derived phosphonic acids Fc(CH2)nP(O)(OH)2 (n=0–2) [Fc=(η5-C5H4)Fe(η5-C5H5)] and 1,1′-Fc′[P(O)(OH)2]2 [Fc′=Fe(η5-C5H4)2] in the presence of Ag2O. The complexes have been characterised by NMR spectroscopy, together with crystal structure determinations on [Fc(CH2)nPO3Pt(PPh3)2] (n=1, 2) and [1,1′-Fc′{PO3Pt(PPh3)2}2]. The complexes [Fc(CH2)nPO3Pt(PPh3)2] (n=1, 2) show moderate activity against P388 leukaemia cells, whereas the parent phosphonic acids are inactive.