Structural variations in the ligands around a simple oxo-centered building block, the tetrahedral [M4O]6+ unit, M=Mn and Fe

Cotton, F. Albert; Daniels, Lee M.; Jordan, Glenn T.; Murillo, Carlos A.; Pascual, Isabel

doi:10.1016/s0020-1693(99)00252-2

Cited by 34 publications

(22 citation statements)

References 15 publications

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“…25 The assignment of the redox states in the triiron core as [Fe II 2 Fe III ] is completed by assigning the isomer shift at δ = 0.452 mm/s (solid orange trace) with a quadrupole splitting of |Δ E Q | = 1.188 mm/s as a high-spin ferric center.25 Metal clusters featuring a nearly identical [Fe 4 ( μ 4 -O)] core, exhibit similar Mössbauer parameters for high-spin Fe centers. 18,19b,25 Overall the observed Mössbauer parameters are in-line with other six-coordinate Fe II /Fe III centers bearing N- and O-donor atoms. 26 and nearly identical to those observed for the [Fe II 2 Fe III ] triiron core in our previously reported oxido/hydroxido scandium complex.…”

Section: Resultssupporting

confidence: 77%

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

et al. 2015

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A series of tetranuclear iron complexes displaying a site-differentiated metal center were synthesized. Three of the metal centers are coordinated to our previously reported ligand, based on a 1,3,5-triarylbenzene motif with nitrogen and oxygen donors. The fourth (apical) iron center is coordinatively unsaturated and appended to the trinuclear core through three bridging pyrazolates and an interstitial μ4-oxide moiety. Electrochemical studies of complex [LFe3(PhPz)3OFe][OTf]2 revealed three reversible redox events assigned to the FeII4/FeII3FeIII (−1.733 V), FeII3FeIII/FeII2FeIII2 (−0.727 V), and FeII2FeIII2/FeIIFeIII3 (0.018 V) redox-couples. Complexes in all redox states were isolated, and three were characterized structurally by single crystal X-ray diffraction. Combined Mössbauer spectroscopic and crystallographic studies indicate that the change in oxidation state is exclusively localized at the triiron core, without changing the oxidation state of the apical metal center. This phenomenon is assigned to differences in the coordination environment of the two metal sites in the cluster, and provides a strategy for storing electron and hole equivalents without affecting the oxidation state of the coordinatively unsaturated metal. The presence of an additional single ligand-binding site allowed for study of the effect of redox modulation on nitric oxide activation by an FeII metal center. Treatment of the clusters with nitric oxide resulted in binding of NO to the apical iron center generating a {FeNO}7 moiety. As with the NO-free precursors, three reversible redox events are observed electrochemically and are localized at the iron centers distal from the NO ligand. Altering the redox state of the triiron core resulted in significant change in the NO stretching frequency, by as much as 100 cm−1, indicative of NO activation modulated by remote metal centers. The increased activation of NO is attributed to structural changes within the clusters, in particular related to the interaction of the metal centers with the interstitial atom. The differences in NO activation were further shown to lead to differential reactivity, with NO disproportionation with N2O formation performed by the more electron rich cluster.

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Section: Resultssupporting

confidence: 77%

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

et al. 2015

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“…Thus, all iron atoms exhibit a coordination number of five (two N, O, Cl, P). Such a tetrahedral (Fe 4 O) 6+ unit was observed earlier by, for example, Cotton et al, [30,31] The oxygen source was most probably the THF solvent which was oxidized and cleaved by iron(III). Similar to the Ntrialkylsilyl-substituted 2-pyridylmethylamides, no complexes of iron(III) with (2-pyridylmethyl)(diphenylphosphanyl)amides were observed.…”

Section: Resultssupporting

confidence: 65%

Influence of N‐Substitution on the Oxidation of 2‐Pyridylmethylamines with Bis(trimethylsilyl)amides of Iron(III) – Synthesis of Heteroleptic Iron(II) 2‐Pyridylmethylamides

et al. 2011

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The reaction of (thf)Fe[N(SiMe3)2]2Cl with (2‐pyridylmethyl)(diphenylphosphanyl)amine (1) in hot tetrahydrofuran (THF) yields dinuclear [(ClFe)2{μ‐N(SiMe3)2}{Ph2P(NCH2Py)2}] (2) and [ClFe{Ph2P(O)‐NCH2Py}]2 (3) with the oxygen atom stemming from THF degradation. The formation of 2 requires a P–N bond cleavage and reformation leading to the tetradendate diphenyl‐bis(2‐pyridylmethylamido)phosphonium ion. If this reaction of (thf)Fe[N(SiMe3)2]2Cl with 1 is performed at room temperature, no P–N bond cleavage is observed. Instead of that, ether degradation occurs yielding [Fe4(μ4‐O)(μ2‐Cl)2(Ph2P‐NCH2Py)4] (4) with a central oxygen‐centered iron tetrahedron as well as complex 3. Recrystallization of 3 from dichloromethane leads to addition of HCl and to the formation of [FeCl2·{Ph2P(O)‐N(H)‐CH2Py}] (5). The phosphonium ion of 2 is isoelectronic to the corresponding diphenyl‐bis(2‐pyridylmethylamino)silane (6). Lithiation of 6 followed by a metathetical reaction with (thf)2FeCl2 yields the trinuclear complex [Fe3Cl2{Ph2Si(NCH2Py)2}2] (7) with antiferromagnetic interactions.

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“…Unfortunately, for XIRFIN, the atomic coordinates are not available, and therefore the representation of its Fe 4 (μ 4 -O) core cannot be sketched. However, Cotton et al 34 have shown that this tetrairon(II) unit is tetrahedral as well. Thus, the present Fe III 4 (μ 4 -O) unit ( Figure 2) corresponds to the first isolated μ 4 -oxido iron(III) system reported so far, which moreover exhibits an almost square-planar geometry.…”

Section: Resultsmentioning

confidence: 99%

“…The aerobic reaction of iron(II) perchlorate with the ligand Hbisi in methanol produces the compound [Fe 4 (μ 4 -O)(μ-MeO) 4 -(bisi) 4 ](ClO 4 ) 2 3 4MeOH (1), whose single-crystal X-ray structure reveals a Fe III 4 (μ 4 -O) unit. Such discrete Fe 4 (μ 4 -O) units are extremely rare; actually, [Fe II 4 (μ 4 -O)] 6þ cores have been observed, with various geometries, only in three coordination compounds, namely, [Fe 4 O(dpa) 6 ] 3 2toluene (dpa = anion of the dipyridylamine; CSD refcode XIRFIN), 34 [Fe 4 O-(DPhF) 6 ] 3 1.5toluene (DPhF = N,N 0 -diphenylformamidinate; CSD refcode NEKXOQ), 35 and [Fe 4 O(MBT) 6 ] (MBT = 2-mercaptobenzothiazole; CSD refcode HEQVAB). 36 To the best of our knowledge, a discrete, square-planar [Fe III 4 (μ 4 -O)] 10þ core has never been reported so far.…”

Section: Introductionmentioning

confidence: 99%

Discrete Tetrairon(III) Cluster Exhibiting a Square-Planar Fe₄(μ₄-O) Core: Structural and Magnetic Properties

et al. 2010

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The aerobic reaction of the Schiff-base ligand N-(benzimidazol-2-yl)salicylaldimine (Hbisi) with iron(II) perchlorate in methanol leads to the formation of the remarkable coordination compound [Fe(4)(mu(4)-O)(mu-MeO)(4)(bisi)(4)](ClO(4))(2) x 4 MeOH (1), whose single-crystal X-ray structure reveals the presence of a discrete Fe(III)(4)(mu(4)-O) core. Magnetic and Mossbauer studies both show that the exchange interaction within the square tetranuclear iron(III) unit is dominated by the central bridging mu(4)-oxido ligand, the involvement of the mu-methoxido bridges being negligible.

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Structural variations in the ligands around a simple oxo-centered building block, the tetrahedral [M4O]6+ unit, M=Mn and Fe

Cited by 34 publications

References 15 publications

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

Influence of N‐Substitution on the Oxidation of 2‐Pyridylmethylamines with Bis(trimethylsilyl)amides of Iron(III) – Synthesis of Heteroleptic Iron(II) 2‐Pyridylmethylamides

Discrete Tetrairon(III) Cluster Exhibiting a Square-Planar Fe₄(μ₄-O) Core: Structural and Magnetic Properties

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Structural variations in the ligands around a simple oxo-centered building block, the tetrahedral [M4O]6+ unit, M=Mn and Fe

Cited by 34 publications

References 15 publications

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

Nitric Oxide Activation by Distal Redox Modulation in Tetranuclear Iron Nitrosyl Complexes

Influence of N‐Substitution on the Oxidation of 2‐Pyridylmethylamines with Bis(trimethylsilyl)amides of Iron(III) – Synthesis of Heteroleptic Iron(II) 2‐Pyridylmethylamides

Discrete Tetrairon(III) Cluster Exhibiting a Square-Planar Fe4(μ4-O) Core: Structural and Magnetic Properties

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Discrete Tetrairon(III) Cluster Exhibiting a Square-Planar Fe₄(μ₄-O) Core: Structural and Magnetic Properties