Coordination of Aza Heterocycles with Macroheterocyclic Metal Complexes in Amphiprotic Media: II. Kinetics of Outer-Sphere Ligand Exchange in Chromium(III) Tetrphenylporphyrinate

Rate constants and activation parameters for substitution of alcohols with aza heterocycles in the chromium(III) (acetate)tetraphenylporphyrinate complex were calculated. The nature of the leaving ligand significantly affects the activation parameters. Increased strength of the H bond in the outer coordination sphere of the macrocyclic complex decreases the substitution rate constant. The logarithms of the reaction rate constants linearly vary with heteroring basicity. An SN2 mechanism and an appreciable effect of the heteroring on the transition state are suggested.