The cytotoxicities of two platinum(IV) complexes of formula [PtX
2(eddp)]
·nH
2O (eddp=ethylenediamine-
N,
N′-di-3-propionate, X=chloro [I] or bromo [II],
n=1 or 1.24) are reported. The complexes have been obtained by direct reaction of potassium hexahaloplatinate(IV) with H
2eddp
·2HCl followed by addition of a base (LiOH). The crystal and molecular structure has confirmed that the complex with bromo
ligands, similarly to the complex with chloro
ligands previously reported, has
trans configuration of the halogens. In both the chloro and bromo complexes there appear to be intramolecular N–H
X interactions which account for a narrowing of the corresponding X–Pt–N angles below 90°. The
trans isomer (configuration index
OC-6-13, two nitrogens and two oxygens of eddp bound in the equatorial plane) is the only one obtained in the reaction of hexahaloplatinate(IV) with the eddp
ligand while a similar reaction performed with ethylenediamine-
N,
N′-diacetate (
edda) affords exclusively the symmetrical
cis-isomer (configuration index
OC-6-33, equatorial nitrogen and axial oxygen atoms of
edda). The longer chain of the propionato groups (as compared to the acetato ones) is responsible for such a change in preferred configuration. NMR data have revealed a very large diastereotopic splitting of the propionato methylene protons
α to the nitrogens (0.88 ppm). The
trans disposition of the halogen
ligands in the compounds with eddp leads to deactivation of platinum(IV) complexes in comparison to those with
edda having
cis disposition of the leaving chlorides (human ovarian cancer cell line A2780, IC
50 [μM] of 92.6±12 and 30.3±7.5 for [I] and [II], respectively).