Preparation and characterization of mu-nitrido diiron phthalocyanines with electron-withdrawing substituents: application for catalytic aromatic oxidation.
Mu-nitrido-bis [tetra-(hexyl-sulfonyl)phthalocyaninatoiron] (3a) and mu-nitrido-bis [tetra-(tert-butylsulfonyl) phthalocyaninatoiron] (3b) complexes have been prepared and fully characterized by electrospray ionization mass spectrometry, UV-Vis, FTIR, EPR, Mössbauer techniques as well as by X-ray photoelectron and Fe K-edge X-ray absorption spectroscopies. Small changes at the periphery of the phthalocyanine ligand introduce a difference in the iron oxidation state. While 3b with tert-butyl substituents is a neutral complex with a mixed-valence Fe(3.5)-N-Fe(3.5) structural unit, 3a having n-hexyl substituents is an oxidized cationic Fe(IV)-N-Fe(IV) complex. The structural parameters of N-bridged diiron phthalocyanine with a Fe(3.5)-N-Fe(3.5) unit were determined for the first time. Iron atoms in 3b are displaced out of plane by 0.24 A and the Fe-N bond distance of the linear Fe-N-Fe fragment is equal to 1.67 A. Both complexes selectively catalyze benzylic oxidation of alkyl aromatic compounds by tBuOOH. Toluene was oxidized to benzoic acid with 80% selectivity, and the total turnover number was as high as 197. p-Toluic acid was the principal product of p-xylene oxidation. In this case the turnover number achieved 587 substrate molecules per molecule of catalyst. The described catalytic system is complementary to the recently reported system based on mu-nitrido diiron tetrabutylphthalocyanine-H2O2 which effectively oxidizes the benzene ring.
Işci
Umit
U
Institut de Recherches sur la Catalyse et l'Environnement de Lyon IRCELYON, UMR 5256, CNRS Université Lyon 1 2, av. A. Einstein, 69626 Villeurbanne Cedex, France.
Afanasiev
Pavel
P
Millet
Jean-Marc M
JM
Kudrik
Evgeny V
EV
Ahsen
Vefa
V
Sorokin
Alexander B
AB
D002384:Catalysis; D020134:Catalytic Domain; D004798:Enzymes / Q000737:chemistry; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D054833:Isoindoles; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D014992:Xylenes / Q000737:chemistry
D004798:Enzymes; D005296:Ferrous Compounds; D007211:Indoles; D054833:Isoindoles; D014992:Xylenes; C545286:mu-nitrido-bis (tetra-(hexyl-sulfonyl)phthalocyaninatoiron); C545287:mu-nitrido-bis (tetra-(tert-butylsulfonyl) phthalocyaninatoiron); C031286:4-xylene; D007501:Iron; C013647:phthalocyanine