PHOTOCATALYTIC OXYGENATION OF SELECTED ALKENES WITH DIOXYGEN ACTIVATED BY (TETRAARYLPORPHYRINATO)IRON(III) AND (TETRAARYLPORPHYRINATO)MANGANESE(III) COMPLEXES

Photocatalytic oxygenation of B-pinene and a-methylstyrene in the pres ence of dioxygen and (tetraaryl-porphyrinato)iron(III) or -manganese(I II) complexes yields allylic oxygenation products, epoxides and partia lly autoxidation products. The product composition was found to be inf luenced by the nature of substrates used, the concentration and the te mperature. Photochemical excitation of Soret states of the porphyrinat o complexes leads to redox reactions. As a result coordinatively unsat urated metal(II) porphyrinato complexes are formed, which are able to activate molecular oxygen. The proposed reaction mechanism involves a highly valent oxometal(IV) porphyrinate as the catalytically active sp ecies. Hydrogen abstraction of the organic substrate in allylic positi on, ''direct'' oxygen transfer and catalysed autoxidation are consider ed to be the most probable reaction pathways of the catalytically acti ve species.