Abstract: Platinum complexes are disclosed in which the platinum cation is coordinated to heterocyclic sulfur compounds as well as monodentate or bidentate amines. The complexes have the formula: ##STR1## wherein L.sub.1 and L.sub.2 are individually ammonia or monodentate amine ligands or L.sub.1 and L.sub.2 together are a bidentate amine ligand, S* is sulfur and R.sub.1 and R.sub.2 taken together with S are thiophene, thiazole, benzothiazole or benzothiophene. These platinum complexes, which have anti-neoplastic activity, are synthesized by reacting sulfonated heterocyclic sulfur compounds with diamines of platinum nitrate.