Solvent dependence of the stereochemistry of base-catalyzed solvolysis of trans-[Co(NH3)4(15NH3)X]3+/2+(X = Me2SO or Cl) ions

Abstract

The cis–trans product ratio for the base-catalyzed solvolysis of the ¹⁵NH₃ labelled trans-[Co(NH₃)₄(¹⁵NH₃)Cl]²⁺ ion has been determined as a function of the solvent. The solvents used were H₂O–CH₃OH and H₂O–dmso (dimethyl sulphoxide) mixtures, as well as anhydrous CH₃OH and CH₃NH₂. The trans-[Co(NH₃)₄(¹⁵NH₃)(dmso)]³⁺ ion was included also in the study. The base hydrolysis results do not show any solvent or leaving-group dependence, within experimental error (2%). All trans systems give (44 ± 1)% rearrangement. Small, significant differences are shown by the penta-amminechloro-complex in CH₃NH₂(50% rearrangement) and by the dmso complex (48% rearrangement in H₂O and 46% in CH₃OH). The results are interpreted as indicating the adequacy of a mechanistic model involving a five-co-ordinate intermediate.