A Trinuclear Iron(III) Complex Containing the Semi‐Cubane [Fe₃(μ₃‐O)]⁷⁺ Core: Structural, Spectroscopic, Magnetic and Electrochemical Study

Abstract

A trinuclear iron(III) oxo‐centered complex [Fe3(μ3‐O)(3‐OCH3‐salnec)3]OH·5H2O was synthesized and characterized as cluster containing the semi‐cubane [Fe3(μ3‐O)]7+ core. The central oxygen atom is bridging the three iron(III) ions, which form an equilateral triangle with an average edge of –3.00 Å as it was deduced from X‐ray diffraction studies. The new tetradentate ligand 3‐OCH3‐salnecH2 = 1‐[1‐hydroxy‐2‐(9′‐methyl‐1,10′‐phenanthrolin‐2‐yl)ethyl]‐3‐methoxyphenol‐2, was generated “in situ” during the synthesis process as a product of the addition reaction between the starting ligands 2,9‐dimethyl‐phenanthroline(neoc) and 3‐methoxy‐salicylaldehyde(3‐OCH3‐saloH2), in the presence of sodium methoxide and Fe3+. Variable‐temperature magnetic measurements indicate antiferromagnetic exchange interactions between the iron(III) ions in the cluster. Additionally, spectroscopic (IR, UV/Vis, Mössbauer, EPR) and electrochemical studies (CV) are presented and discussed.

Polynuclear Iron-Oxo/Hydroxy Complexes of Ketoacidoximate Ligands: Synthesis, Structures and Conversion to Ferric Oxide

“…The absorption bands at the lower energy level, 370, 400 and 470 nm for 1–3 , respectively, can be assigned to the ligand to metal charge transfer (LMCT) bands. Similar value of 480 nm was reported for [Fe 3 (μ 3 ‐O)(3‐OCH 3 ‐salnec) 3 ]OH⋅5H 2 O complex.…”

“…The UV‐Vis spectra of 1–3 were recorded in methanol (Figure ). The absorption bands observed at 290, 245 and 240 nm for 1–3, respectively, could be assigned to π→π* or n→π* transitions of the carbonyl or oxime or the phenyl groups of the ligands …”

Structure, spectroscopy, stability, and bridge exchange in the M3O4 incomplete-cubane complexes, [M(III)3(Sal-AHA)3(μ-OR)]− (M = Fe, Ga)

“…The maximum intensity of the g = 4.3 signal occurring at ~ 15 K corresponds to only 10 cm -1 separating the associated excited state from the ground S = ½ level. This suggests that the coupling is much weaker in the methoxy-bridged cluster 2 than in the sulfido-bridged cluster of ferredoxin [17] and the oxobridged analog reported previously [8]. These low energy spin states can be described using the model of Kent, et al [24].…”

“…Na[Fe(III) 3 (3,5-diCl-Sal-AHA) 3 ( 3 -OCH 3 )] is one of only a few crystallographicallycharacterized, isolated Fe 3 O 4 clusters with the incomplete cubane structure that have been reported [7][8][9][10][11]. In order to further understand the structural and magnetic aspects of this complex and its potential reactivity, the d 10 Ga(III) complex was synthesized for comparison.…”

Heterometallic Triiron-Oxo/Hydroxo Clusters: Effect of Redox-Inactive Metals

“…S8), in good agreement with literature values for Fe II/III compounds bearing N/O ligands. 15 The Fe(2)–O(5)H bond in 2 -Sc is elongated compared to 1 -Ca and 1 -Sr likely due to a combination of a more reduced Fe 3 core and a stronger interaction of the bridging moieties with the more Lewis acidic Sc 3+ . The one-electron reduced Ca compound ( 2 -Ca) was obtained by the chemical reduction of 1 -Ca using one equivalent of cobaltocene (CoCp 2 ; E O ~ −1.33 V vs. Fc/Fc + ) in CH 2 Cl 2 (Scheme 1).…”