Mechanistic study of the substitution reactions of [Pt(II)(bis (2-pyridylmethyl)amine)H2O](ClO4)2 and [Pt(II)(bis (2-pyridylmethyl)sulfide)H2O](ClO4)2 with azole Nucleophiles. Crystal structure of [Pt(II)(bis(2-pyridylmethyl)sulfide) Cl]ClO4

The substitution kinetics of the complexes [Pt(II)(bis(2-pyridylmethyl) amine) H2O](ClO4)(2), Ptdpa and [Pt(II)(bis(2-pyridylmethyl) sulfide) H2O](ClO4)(2), Ptdps, with a series of azole nucleophiles: Imidazole (Im), 1-methylimidazole (MIm), 1,2-Dimethylimidazole (DIm), 1,2,4-triazole (Trz) and pyrazole (Pyz), were studied in an aqueous medium at constant ionic strength (0.1 M NaClO4). The substitution of the coordinated water ligand on the Pt(II) complexes by the azoles was studied under pseudo-first order conditions as a function of the incoming nucleophiles concentration and temperature using either stopped-flow techniques or UV-Vis spectroscopy. Ptdps was found to be more reactive (three magnitude higher) than Ptdpa. The second-order rate constant, k(2), for all the nucleophiles ranged between 0.087 +/- 0.005 and 0.926 +/- 0.05 M-1 s(-1) for Ptdpa and between 146 +/- 4 and 1458 +/- 10 M-1 s(-1) for Ptdps. The rate of substitution of the aqua ligand is dependent on the strength of the r-donor character and the p-acceptability of the trans atom to the leaving group. The observed reactivity trend for the azoles followed the trend, MIm > Im > DIm > Trz > Pyz. This reactivity trend correlates with the basicity, steric and electrophilic effects of the nucleophiles. The X-ray crystal structure of Ptdps-Cl is reported. (C) 2017 Elsevier B.V. All rights reserved.