The serendipitous discovery of the anti-tumour activity of cisplatin [cis-PtCI₂(NH₃)₂] in 1969 has led to increased interest in the development of new metal-based anti-cancer drugs. However, regardless of the large numbers of new metal-containing compounds generated, many of which demonstrate anti-tumour activity, cisplatin still remains one of the most widely used anti-tumour drugs in the western world.