Synthesis and crystal structure of cis-diammineplatinum .alpha.-pyridone blue

The blue compounds formed from aqueous solutions of platinum(II) in the presence of amides have been a subject of study since the original report of “Platinblau” in 1908.[1-3] Recent interest in these complexes was sparked by the discovery that aquated products of the antitumor drug cis-dichlorodiammineplatinum(II) undergo a slow reaction with polyuracil, uracil, thymine, and related pyrimidines (1) to form blue complexes. [4] The platinum pyrimidine blues have antitumor activity of their own [4,5] and are useful electron microscopic stains for DNA.[6] Attempts to crystallize these blue complexes have been largely unsuccessful because they are oligomeric mixtures of varying degrees of hydrolytic instability.[7] With synthetic insights provided by the detailed studies of Lerner [7] and the choice of α-pyridone (2) as the amide ligand [8], we have obtained a crystalline platinum blue and determined its structure by x-ray crystallography.