The hydrolysis products of cis-dichlorodiammineplatinum(II) 3. Hydrolysis kinetics at physiological pH

Abstract

The rate of hydrolysis of cis-PtCl 2(NH 3) 2 has been measured in non-buffered aqueous solution ( I = 0.2 M NaClO 4; T = 45.0 °C) at constant pH over the range pH = 4.0−8.5 using a combined pH-stat/ spectrophotometric technique. The hydrolysis rate at pH = 7.4 ( T = 45.0 °C) was also determined with [Cl −] = 0.0−0.1 M ( I = 0.2 M; NaCl, NaClO 4). At the end of each kinetic run, the resulting solution was made 0.2 M in Cl − by the addition of NaCl and the reverse (anation) reaction was monitored, again under constant pH conditions. A knowledge of the complete pH-rate profile, with and without added chloride ion, allows current models for the hydrolysis of cis-PtCl 2(NH 3) 2 under physiological conditions, to be tested. cis-Pt(NH 3) 2(OH 2) 2 2+ is considered to be the least important of all the potential hydrolysis products available to bind to replicating DNA at pH = 7.4.