A 195Pt nuclear magnetic resonance spectroscopy study of the solvolysis of sodium hexachloroplatinate by dimethyl sulfoxide.

Abstract

Platinum-195 Fourier transform nuclear magnetic resonance spectroscopy was used to study the reaction of sodium hexachloroplatinate with dimethyl sulfoxide-dg in the mixed solvent dimethyl sulfoxide-dg: water, 1:2, V/V.

The reaction was observed at several temperatures over uniform time intervals to ascertain the temperature dependence of the rate of the reaction. The spectra generated were integrated to determine the extent to which the reaction had proceeded at the different temperatures as a function of time. Rate constants for the reaction at each of the temperatures were then calculated from linear regression analyses of the spectral integration values. The value at 59.4°C is 1.31 x 10“^ s~^. An Arrhenius plot of these rate constants was made and from this several kinetic activation parameters were calculated.

Finally, the reaction was submitted to long duration temperature equilibration experiments to ascertain the thermodynamic equilibrium constant and therefore the molar free energy change for the reaction and any variation in this value as a function of temperature. From the temperature dependence, the molar enthalpy change for the reaction was obtained. Finally, the molar entropy change was calculated. The values at 59.4°C were 0.9 KJ mol~^, -45.1 KJ mol"l and -138 J K“^ mol”^, respectively.