AbstractThe diastereomeric 1‐(fluoro/difluorophenyl)‐2‐phenylethylenediamines (4‐fluoro:erythro‐1/threo‐1; 2,4‐difluoro:erythro‐2/‐threo‐2; 2,6‐difluoro:erythro‐3/threo‐3) and the diastereomeric 1‐(4‐fluorophenyl)‐2‐(3‐hydroxyphenyl)ethylenediamines (erythro‐4/‐threo‐4) were synthesized from appropriately substituted stilbenes by reaction with IN3and subsequent LiAlH4reduction. Coordination of the 1,2‐diphenylethylenediamines to platinum was carried out by use of K2PtI4. The water‐soluble aquasulfatoplatinum(II) complexes (erythro/threo‐1‐PtSO4‐erythro/threo‐4‐PtSO4) were obtained from the diiodoplatinum(II) complexes by reaction with Ag2SO4. Additionallyerythro/threo‐4‐PtSO4anderythro/threo‐4‐PtSO4were transformed into the dichloroplatinum(II) complexes (erythro/threo‐1‐PtCl2,erythro/threo‐4‐PtCl2) by treatment with KCl. In contrast to the less effectiveerythro‐configurated sulfatoplatinum(II) complexes thethreo‐analogues showed comparable or even superior activities to cisplatin on the human MDA‐MB‐231 breast cancer cell line. On the MXT‐M‐3.2 breast cancer of the mouse onlyerythro‐ andthreo‐4‐PtSO4caused similar effects like cisplatin. The strong inhibitory effect of the diastereomeric sulfatoplatinum(II) complexes on the P‐388 leukemia of the mouse was equal to that of cisplatin. On the latter