[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)((NH3)-N-15)(2)] (X = Cl-, O2CCH3-, OH-) have been followed by [H-1, N-15] 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((NH3)-N-15)(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((NH3)-N-15)(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.