The subject of the present invention is to provide a novel platinum (IV) complex characterized by having stronger antitumor activity against malignant tumors and relatively reduced side effects. The solving means is a platinum (IV) complex using cis, cis-spiro[4,4]nonane-1,6-diamine or an optical active diamine thereof as a ligand, particularly a tetravalent platinum dichloromalonate salt complex represented by the formula (G) using (S,S,S)-cis, cis-spiro[4,4]nonane-1,6 diamine as a ligand.本發明之課題在於提供一種新穎四價鉑錯合物,其具有如下特徵:對惡性腫瘤有較強之抗腫瘤性活性,且相對地減輕副作用。解決手段為一種以順,順-螺[4,4]壬烷-1,6-二胺及其光學活性二胺為配位基之四價鉑錯合物,特別是下式(G)所表示之以(S,S,S)-順,順-螺[4,4]壬烷-1,6二胺為配位基的四價鉑二氯丙二酸鹽錯合物。
