High-pressure effects on the proton nuclear magnetic resonance spectra of palladium(II) complexes of cyclic sulphides. Estimation of activation volumes for inversion about sulphur

Abstract

The dynamic ¹H n.m.r. spectra of the complexes trans-[PdBr₂([graphic omitted]H₂)₂], trans-[PdCl₂([graphic omitted]H₂)₂], and trans-[PdCl₂{[graphic omitted]H₂)₅}₂] in CHCl₃ and trans-[PdCl₂([graphic omitted]H₂)₂] in CH₂Cl₂ solvent have been measured for pressures up to 220 MPa. In each case a very small (0 ± 2 cm³ mol^–1) volume of activation is found. These ΔV‡ values indicate no dissociative, associative, or solvent participation in the inversion process at sulphur, and substantiate the proposal that the major contribution to the entropy is the reorganizational effect on achieving ring planarity.