G. Crisponi et al., Spectrophotometric and potentiometric study on platinum(II) chelates of mercapto carboxylic acids, POLYHEDRON, 19(24-25), 2000, pp. 2435-2440
The coordination of Pt(II) with different mercapto and dimercapto compounds
has been studied using both potentiometric titration at 25 degreesC in KCl
0.1 M and UV-Vis spectroscopy. The slow complex formation kinetics has bee
n followed spectrophotometrically for several days on samples with differen
t ligand molar fractions ranging from 0.1 to 1, keeping the ligand and meta
l concentration below 8 x 10(-4) M. For the potentiometric titration, the l
igand concentrations were kept constant at 10(-3) M, and the 0.25, 0.5, 0.7
5 and 1.00 metal/ligand ratios were titrated in the pH range 2.5-11 for eac
h ligand. The solutions were kept in a thermostatted bath at 25 degreesC fo
r 2 days before titration. The stabilization of the absorbance values under
these conditions after 2 days, and the back titration with hydrochloric ac
id 0.1 M, led us to conclude that the proper equilibrium complex formation
is reached under these conditions. Using KCl 0.1 M as an ionic strength med
ium, the reported formation constants are referred to the complexation reac
tion starting from [PtCl4](2-). Some models are proposed on the basis of th
e estimated stoichiometries. (C) 2000 Elsevier Science B.V. All rights rese
rved.