Variable-temperature 1H n.m.r. spectra have been recorded for (RSC2H4SR) MX2(R = Me, Et, Prn, Pri, or Bun; M = Pt or Pd; X = Cl, Br, or I). The pyramidal conformation at sulphur allows the detection of meso and (±)-isomeric forms at low temperatures. At higher temperatures, rapid interconversion of these isomers leads to the observation of ‘averaged’ spectra corresponding to a weighted mean of the parameters of the individual conformers. The interconversion process is inversion at single sulphur atoms. The rate of inversion increases as the trans-influence of X increases, and this appears to be an inductive effect. Inversion in the palladium compounds is more rapid than in the platinum derivatives.
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Cross et al. (1972) studied this question.