Resonance Raman evidence for the interconversion between an [FeIII–η1-OOH]2+ and [FeIII–η2-O2]+ species and mechanistic implications thereof

The deprotonation of [FeIII(N4Py)(η1-OOH)]2+ 1 gives [FeIII(N4Py)(η2-OO)]+ 2, as unequivocally demonstrated by resonance Raman spectroscopy, and leads to the loss of alkane hydroxylation activity by 1

Iron Chemistry of a Pentadentate Ligand That Generates a Metastable FeIII-OOH Intermediate

In an effort to gain more insight into the factors controlling the formation of low-spin non-heme FeIII-peroxo intermediates in oxidation catalysis, such as activated bleomycin, we have synthesized a series of iron complexes based on the pentadentate ligand N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine). The following complexes have been prepared: [(N4Py)FeII(CH3CN)](ClO4)2 (1), [(N4Py)FeIICl](ClO4) (2), [(N4Py)FeIIIOMe](ClO4)2 (3), and [(N4Py)2Fe2O](ClO4)4 (4). Complexes 1 and 2 have low- and high-spin FeII centers, respectively, whereas 3 is an FeIII complex that undergoes a temperature-dependent spin transition. The iron centers in the oxo-bridged dimer 4 are antiferromagnetically coupled (J = -104 cm-1). Comparison of the crystal structures of 1, 3, and 4 shows that the ligand is well suited to accommodate both FeII and FeIII in either spin state. For the high-spin FeIII complexes 3 and 4 the iron atoms are positioned somewhat outside of the cavity formed by the ligand, while in the case of the low-spin FeII complex 1 the iron atom is retained in the middle of the cavity with approximately equal bond lengths to all nitrogen atoms from the ligand. On the basis of UV/vis and EPR observations, it is shown that 1, 3, and 4 all react with H2O2 to generate the purple low-spin [(N4Py)FeIIIOOH]2+ intermediate (6). In the case of 1, titration experiments with H2O2 monitored by UV/vis and 1H NMR reveal the formation of [(N4Py)FeIIIOH]2+ (5) and the oxo-bridged diiron(III) dimer (4) prior to the generation of the FeIII-OOH species (6). Raman spectra of 6 show distinctive Raman features, particularly a ν(O-O) at 790 cm-1 that is the lowest observed for any iron-peroxo species. This observation may rationalize the reactivity of lowspin FeIII-OOH species such as “activated bleomycin”.

CCDC 119260: Experimental Crystal Structure Determination

Related Article: G.Roelfes, M.Lubben, Kui Chen, R.Y.N.Ho, A.Meetsma, S.Genseberger, R.M.Hermant, R.Hage, S.K.Mandal, V.G.Young Junior, Yan Zang, H.Kooijman, A.L.Spek, L.Que Junior, B.L.Feringa|1999|Inorg.Chem.|38|1929|doi:10.1021/ic980983p,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 119262: Experimental Crystal Structure Determination

Related Article: G.Roelfes, M.Lubben, Kui Chen, R.Y.N.Ho, A.Meetsma, S.Genseberger, R.M.Hermant, R.Hage, S.K.Mandal, V.G.Young Junior, Yan Zang, H.Kooijman, A.L.Spek, L.Que Junior, B.L.Feringa|1999|Inorg.Chem.|38|1929|doi:10.1021/ic980983p,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 119261: Experimental Crystal Structure Determination

Related Article: G.Roelfes, M.Lubben, Kui Chen, R.Y.N.Ho, A.Meetsma, S.Genseberger, R.M.Hermant, R.Hage, S.K.Mandal, V.G.Young Junior, Yan Zang, H.Kooijman, A.L.Spek, L.Que Junior, B.L.Feringa|1999|Inorg.Chem.|38|1929|doi:10.1021/ic980983p,Related Article: M.van den Heuvel, T.A.van den Berg, R.M.Kellogg, C.T.Choma, B.L.Feringa|2004|J.Org.Chem.|69|250|doi:10.1021/jo035157z,Related Article: A.Draksharapu, Qian Li, H.Logtenberg, T.A.van den Berg, A.Meetsma, J.S.Killeen, B.L.Feringa, R.Hage, G.Roelfes, W.R.Browne|2012|Inorg.Chem.|51|900|doi:10.1021/ic201879b,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.