Dynamic NMR as a Nondestructive Method for the Determination of Rates of Dissociation. XVI. Mechanism of Sulfur Inversion in Platinum(II)–Thioether Complexes Revisited

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Abstract
The mechanism of sulfur inversion in some platinum(II)–thioether complexes was reinvestigated with the use of the dynamic NMR technique. Activation parameters for the sulfur inversion in [(isopropylthio)acetato-O,S]bis(triphenylphosphine)platinum(II) perchlorate in CDCl3 were obtained by taking advantage of the line shape changes in its 1H NMR spectra at various temperatures as follows: ΔH\eweq 18.0±0.4 kcal mol−1, ΔS\eweq 4.0±1.4 cal mol−1 K−1. The kinetic parameters varied little, though the rates of inversion were determined in other solvents. The entropy of activation and the solvent effects together with the presence of coupling between the phosphine-31P and the methine-1H throughout the temperature range of investigation evidence the sulfur inversion without breaking the Pt–S bond. The sulfur inversion in dichlorobis(dialkyl sulfide)platinum(II) in nonpolar solvents was also concluded to take place without bond breakage.

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