Autocatalytic reduction of dichloro 5, 10, 15,20 tetraphenylporphinatoplatinum (IV) by 1-methylimidazole

Abstract

It was observed that in toluene solution, excess 1-methyl-imidazole (Melm) reduces dichloro 5, 10, 15, 20 tetraphenyl-porphinatoplatinum(IV) ($PtTPPCl_2$) to tetraphenylporphinato-platinum(II) (PtTPP) autocatalytically (Fig.1). There was no Pt(III) intermediate or 1-methylimidazole radical detected by Electron Resonance Spectroscopy (ESR) at 25°C. The reaction was found to be autocatalyzed by the PtTPP product when the 1-methylimidazole to $PtTPPCl_2$ concentration ratio is about $10^4$ or more. From the data obtained it is reasonable to suppose that aggregation of the PtTPP product with $PtTPPCl_2$ plays an important role in this reduction process.