Oxoferryl complexes of the halogenated (porphinato)iron catalyst: (Tetrakis(2,6-dichlorophenyl)porphinato)iron

A. Gold*, K. Jayaraj, P. Doppelt, R. Weiss, G. Chottard, E. Bill, X. Ding, A. X. Trautwein

*Corresponding author for this work
100 Citations (Scopus)


Oxidation of (hydroxo)(tetrakis(2,6-dichlorophenyl)porphinato)iron(III) [TPP(2,6-Cl)FeIIIOH] by m-chloroperoxybenzoic acid (mCPBA) in THF or DMF yields the THF and DMF adducts of the oxoferryl complex TPP(2,6-Cl)FeIV=O. Addition of 10-fold molar excess of 1-methylimidazole (l-MeIm) to the TFF adduct gives the corresponding 1-MeIm complex. NMR of the DMF-d7 adduct (200 MHz, DMF-d7, -50 °C) shows proton resonances consistent with an oxoferryl S = 1 structure: 14 ppm (pyrrole H), 4.01 ppm (phenyl m- and p-H) in a ratio of 2:3. The UV-vis spectra (-40 °C) of the red solutions show the band at ~550 nm which is typical of the ferryl oxidation state: (THF) TPP(2,6-Cl)FeIV═O, λmax(∊ X 10'3) 417 (169.5), 551 (10.6), 622 (3.4), 653 (1.4) nm; (DMF) TPP(2,6-Cl)FeIV=O, λmax (∊ X 10-3) 419 (157.6), 554 (11.1), 632 (3.5) nm; (l-Melm) TPP(2,6-Cl)FeIV==O, λmax(∊ X 10-3) 421 (157.5), 561 (13.2), 624 (3.3), 661 (1.8) nm. Resonance Raman bands in the region of the Fe═O stretch provide support for the oxoferryl structure with frequencies that correlate inversely with the strength of the sixth axial ligand: THF (841 cm-1) < DMF (829 cm-1) < 1-Melm (818 cm-1). The Mössbauer spectra, similar to those of other ferryl S = 1 complexes, establish the ferryl oxidation state of iron. While quadrupole splittings vary inversely with axial ligand strength (THF (2 2.08 mm s-1) < DMF (1.81 mm s-1) < 1-Melm (1.35 mm s-1)), isomer shifts are essentially constant. Resonance Raman and Mössbauer data are rationalized by a rearrangement of bonding electron density from Fe 3dx 2_y 2 to 3dz 2 with increasing axial ligand bonding. The Fe═O bond weakens, decreasing νFe═o and the axial electric field gradient decreases, giving smaller quadrupole splitting. However, little net change in electron density at Fe results in constant δ.

Original languageEnglish
JournalJournal of the American Chemical Society
Issue number17
Pages (from-to)5756-5761
Number of pages6
Publication statusPublished - 01.01.1988


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