The axial ligand of a series of iron(III) 5,10,15,20-tetramesitylporphyrin
phenolate complexes was found to exchange with added carboxylic acids and a
lcohols. The rates of axial ligand exchange with carboxylic acids were foun
d to be dependent on acidity of the carboxylic acid, basicity of the phenol
ate, and the steric bulk of both the carboxylic acid and the phenolate axia
l ligand. The rates of axial ligand exchange with alcohols were found to be
dependent on the nucleophilicity of the alcohol, leaving group ability of
the phenolate, and the steric bulk of both the alcohol and the phenolate ax
ial ligand. Different mechanisms for ligand exchange are proposed for carbo
xylic acids and alcohols.