Variable Pressure Oxygen-17 FTNMR and Stopped-Flow Kinetic Study of Water Exchange and DMSO Substitution on Square-Planar Tetraaqua-Palladium(II) and -Platinum(II)

The very slow water exchange on Pt(H2O)42+ was studied in the temperature range 273 to 334 K and pressure range 0.1 to 228 MPa by 17O FTNMR, following the increase in height of the signal from bound water observed when platinum(II) solutions are mixed with 17O enriched water. The much faster water exchange on Pd(H2O)42+ was studied in the temperature range 240 to 345 K and pressure range 0.1 to 260 MPa, by measuring the 17O FTNMR line widths of the bound water resonance at 27.1 and 48.7 MHz. Complex formation between DMSO and Pd(H2O)42+ was studied by stopped-flow, in the temperature range 288 to 309 K and pressure range 0.1 to 175 MPa. In the three cases, the results are interpreted in terms of associative activation modes (a).