[¹H,¹⁵N] Heteronuclear single quantum coherence NMR study of the mechanism of aquation of platinum(IV) ammine complexes

The aquation and hydrolysis of a series of platinum(IV) complexes of the general form cis, trans, cis-[PtCl2(X)2(15NH3)2] (X = Cl−, O2CCH3−, OH−) have been followed by [1H,15N] Heteronuclear Single Quantum Coherence NMR spectroscopy. Negligible aquation (<5%) is observed for the complexes where X = O2CCH3− or OH− over 3−4 weeks. Aquation of cis-[PtCl4(15NH3)2] (1) is observed, and the rate of aquation increases with increasing pH and upon the addition of 0.01 mol equiv of the platinum(II) complex cis-[PtCl2(15NH3)2] (cisplatin). The first aquated species formed from cis-[PtCl4(NH3)2] has one of the axial chloro groups (relative to the equatorial NH3 ligands) replaced by an aqua/hydroxo ligand. The second observed substitution occurs in an equatorial position. Peaks that are consistent with five of the eight possible aquation species were observed in the NMR spectra.\u