Summavy. The equilibrium encrgetics and the kinetics of cis-trans isomerization of some bis(dialkylsulfidc)dihaloplatinum(II) complexes have been examined by lH-NMR. spectroscopy. The isomers are stable in chloroform but each form isomerizes to an equilibrium mixture when free dialkylsulfide is added. The cis to trans process is endothermic and the position of the equilibrium is markedly depcndent on the nature of the donor atoms and of the solvent. Thc rate of isomcrization of Pt(Me2S),Cl, is first order in complex and in Me& The isomerization proceeds by a double displacement mechanism as i t isshown that the tris(dimethylsulfide)chloroplatinum(II) cation is an isolable intermediate of the reaction. When free Me,S is added to tvans-Pd(Me,S),Cl,, isomerization does not occur and onc observes instead a fast ligand exchange. Its mechanism is the usual associative one for substitutions in squarc planar d*-complexes.

Energetik und Kinetik der cis‐trans‐Isomerisierung der Pt(II)‐Komplexe (I) werden NMR‐spektroskopisch untersucht.