A systematic study of the properties and reactivities of iron(III) porphyrin peroxo complexes containing ligands with different electronic properties has been undertaken. While the spectral properties of the peroxo complexes do not show much variation, the stability of the complexes is dramatically increased by employing very electron-poor ligands such as 5,10,15,20-(pentafluorophenyl)porphyrin. The nucleophilicity of the peroxo moiety is decreased considerably by such electron-poor ligands:  unlike all other iron(III) porphyrin peroxo complexes examined here, the perfluorinated peroxo complex does not epoxidize electron-poor olefins. However, this complex appears to have an unusually strong desire for a second axial ligand:  it binds reversibly to triphenylphosphine. This interesting binding pattern is also observed for the perfluorinated iron−chloro complex. None of the complexes are capable of reacting with electron-rich olefins such as tetramethylethylene or with triphenylphosphine. Possible transition states for nucleophilic epoxidation are discussed.

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Peroxo Fe(III), Mn(III), and Ti(IV) porphyrin complexes were reacted with a variety of electron-rich and electron-poor organic substrates in order to compare their reactivities with those of other known metalloperoxide complexes. The peroxoiron(III) porphyrin complex was unreactive with electron-rich substrates such as tetramethylethylene, cyclohexene, triphenylphosphine, or butyllithium but was quite reactive with electron-poor substrates such as 2-cyclohexen-1-one and 2-methyl-1,4-naphthoquinone. The peroxomanganese(III) porphyrin complex was unreactive with these electron-poor olefins but did react with the strongly electron-deficient olefin tetracyanoethylene. The peroxotitanium(IV) porphyrin complex was unreactive with both electron-rich and electron-poor olefins, as well as butyllithium, but did quantitatively oxidize triphenylphosphine to triphenylphosphine oxide. These results lead to the conclusion that the peroxo Fe(III) porphyrin complex is significantly more nucleophilic than the analogous Mn(III) and Ti(IV) complexes and than several well-known nucleophilic non-porphyrin peroxometal complexes.

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