Dataset Information

Structural characterization of the μ-Nitrido Complex {[Fe(OEP)]₂N}

ABSTRACT: The molecular structure of the μ-nitrido dimer, μ-nitrido-bis(2,3,7,8,12,13, 17,18-octaethylporphyrinato)iron, is reported. The axial Fe-N distances average to 1.657 (11) Å and the equatorial distances average to 2.005(5) Å. Although not required by symmetry, the two iron centers appear equivalent and are consistent with an assignment of a low-spin state and a formal oxidation state of +3.5. A comparison of this structure with other nitrido-bridged species is given.

SUBMITTER: Li M

PROVIDER: S-EPMC4221236 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Structural characterization of the μ-Nitrido Complex {[Fe(OEP)]2N}

Li Ming M Scheidt W Robert WR

Journal of porphyrins and phthalocyanines 20140501 5

The molecular structure of the μ-nitrido dimer, μ-nitrido-bis(2,3,7,8,12,13, 17,18-octaethylporphyrinato)iron, is reported. The axial Fe-N distances average to 1.657 (11) Å and the equatorial distances average to 2.005(5) Å. Although not required by symmetry, the two iron centers appear equivalent and are consistent with an assignment of a low-spin state and a formal oxidation state of +3.5. A comparison of this structure with other nitrido-bridged species is given. ...[more]

PMID: 25382965

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Project description:The mixed-valence triiron complexes [Fe3(CO)7-x (PPh3) x (μ-edt)2] (x = 0-2; edt = SCH2CH2S) and [Fe3(CO)5(κ2-diphosphine)(μ-edt)2] (diphosphine = dppv, dppe, dppb, dppn) have been prepared and structurally characterized. All adopt an anti arrangement of the dithiolate bridges, and PPh3 substitution occurs at the apical positions of the outer iron atoms, while the diphosphine complexes exist only in the dibasal form in both the solid state and solution. The carbonyl on the central iron atom is semibridging, and this leads to a rotated structure between the bridged diiron center. IR studies reveal that all complexes are inert to protonation by HBF4·Et2O, but addition of acid to the pentacarbonyl complexes results in one-electron oxidation to yield the moderately stable cations [Fe3(CO)5(PPh3)2(μ-edt)2]+ and [Fe3(CO)5(κ2-diphosphine)(μ-edt)2]+, species which also result upon oxidation by [Cp2Fe][PF6]. The electrochemistry of the formally Fe(I)-Fe(II)-Fe(I) complexes has been investigated. Each undergoes a quasi-reversible oxidation, the potential of which is sensitive to phosphine substitution, generally occurring between 0.15 and 0.50 V, although [Fe3(CO)5(PPh3)2(μ-edt)2] is oxidized at -0.05 V. Reduction of all complexes is irreversible and is again sensitive to phosphine substitution, varying between -1.47 V for [Fe3(CO)7(μ-edt)2] and around -1.7 V for phosphine-substituted complexes. In their one-electron-reduced states, all complexes are catalysts for the reduction of protons to hydrogen, the catalytic overpotential being increased upon successive phosphine substitution. In comparison to the diiron complex [Fe2(CO)6(μ-edt)], [Fe3(CO)7(μ-edt)2] catalyzes proton reduction at 0.36 V less negative potentials. Electronic structure calculations have been carried out in order to fully elucidate the nature of the oxidation and reduction processes. In all complexes, the HOMO comprises an iron-iron bonding orbital localized between the two iron atoms not ligated by the semibridging carbonyl, while the LUMO is highly delocalized in nature and is antibonding between both pairs of iron atoms but also contains an antibonding dithiolate interaction.

Dataset Information

Structural characterization of the μ-Nitrido Complex {[Fe(OEP)]₂N}

Publications

Structural characterization of the <i>μ</i>-Nitrido Complex {[Fe(OEP)]<sub>2</sub>N}

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