Fast exchange between free and co-ordinated ligands in bis(diethyl chalcogen)dihalogeno-palladium(II) and -platinum(II) complexes

Abstract

Variable-temperature n.m.r. spectra show that on addition of free ZEt₂ to [MX₂(ZEt₂)₂](Z = S, Se, or Te; M = Pd or Pt: X = Cl, Br, or I) exchange between free and co-ordinated ligand is fast in each case except for SEt₂–[PtX₂(SEt₂)₂]. The rate of exchange decreases in the orders TeEt₂ SeEt₂ > SEt₂ and Pd > Pt. Coalescences due to chalcogen inversion are quite distinct from the exchange coalescences in the systems SEt₂–[PdX₂(SEt₂)₂] and SeEt₂–[PtX₂(SeEt₂)₂]. This shows for the first time that sulphur inversion in the palladium complexes is not an association–dissociation process.