REACTION OF AN ALPHA-PYRROLIDONATE-BRIDGED CIS-DIAMMINEPLATINUM(II) DIMER WITH MOLECULAR-OXYGEN AND ITS APPLICATION TO THE CATALYTIC O-2 OXIDATION OF HYDROQUINONE

The catalytic effect of [Pt-2(II)(NH3)(4)(C4H6NO)(2)](2+) (Pt-2(II) di mer; C4H6NO = alpha-pyrrolidonate) in the O-2 oxidation of hydroquinon e to quinone is investigated at pH 5. Both the O-2 oxidation of this d imer into [Pt-2(III)(NH3)(4)(C4H6NO)(2)(L)(2)](4+) (Pt-2(III) dimer; L =OH2, OH-, SO42-, etc.) and the re-reduction of the Pt-2(III) dimer in to the Pt-2(II) dimer by hydroquinone were found to be thermodynamical ly favorable. With an excess of hydroquinone, the rate of the catalyti c reaction exceeds that of the former reaction and is roughly linear t o the hydroquinone concentration, suggesting that a certain intermedia te formed in the reaction between the Pt-22(II) dimer and O-2 plays a major role in the present catalysis. In addition, hydrolysis equilibri a for the axial aqua ligands on the Pt-2(III) dimer are investigated s pectrophotometrically.