Syntheses, Mössbauer, and 1H NMR study of some cyclopentadienyliron carbonyl complexes with potentially bidentate amine ligands

Bermejo, María-José; Martı́nez, B.; Vinaixa, Jordi

doi:10.1016/s0022-328x(00)99686-4

Cited by 11 publications

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References 18 publications

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“…The Mössbauer spectra of the two samples under study, the TCNE and TCNQ derivatives (Figure ), do not differ significantly from one another and resemble very much those of the reference samples . The spectra of {(μ 4 -TCNE)[Fe(CO) 2 (C 5 H 5 )] 4 }(BF 4 ) 4 recorded at 260 K (top) and at 85 K (bottom) are shown in Figure .…”

Section: Resultsmentioning

confidence: 89%

Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄

et al. 2007

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The complexes {(mu4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4 were prepared as light-sensitive materials from [Fe(CO)2(C5H5) (THF)](BF4) and the corresponding TCNX ligands (TCNE = tetracyanoethene, TCNQ=7,7,8,8-tetracyano-p-quinodimethane, TCNB=1,2,4,5-tetracyanobenzene). Whereas the TCNE and TCNQ complexes are extremely easily reduced species with reduction potentials>+0.3 V vs ferrocenium/ferrocene, the tetranuclear complex of TCNB exhibits a significantly more negative reduction potential at about -1.0 V. Even for the complexes with strongly pi-accepting TCNE and TCNQ, the very positive reduction potentials, the unusually high nitrile stretching frequencies>2235 cm(-1), and the high-energy charge-transfer transitions indicate negligible metal-to-ligand electron transfer in the ground state, corresponding to a largely unperturbed (TCNX degrees)(FeII)4 formulation of oxidation states as caused by orthogonality between the metal-centered HOMO and the pi* LUMO of TCNX. Mössbauer spectroscopy confirms the low-spin iron(II) state, and DFT calculations suggest coplanar TCNE and TCNQ bridging ligands in the complex tetracations. One-electron reduction to the 3+ forms of the TCNE and TCNQ complexes produces EPR spectra which confirm the predominant ligand character of the then singly occupied MO through isotropic g values slightly below 2, in addition to a negligible g anisotropy of frozen solutions at frequencies up to 285 GHz and also through an unusually well-resolved solution X band EPR spectrum of {(mu4-TCNE)[Fe(CO)2(C5H5)]4}3+ which shows the presence of four equivalent [Fe(CO)2(C5H5)]+ moieties through 57Fe and 13C(CO) hyperfine coupling in nonenriched material. DFT calculations reproduce the experimental EPR data. A survey of discrete TCNE and TCNQ complexes [(mu4-TCNX)(MLn)4] exhibits a dichotomy between the systems {(mu4-TCNX)[Fe(CO)2(C5H5)]4}4+ and {(mu4-TCNQ)[Re(CO)3(bpy)]4}4+ with their negligible metal-to-ligand electron transfer and several other compounds of TCNE or TCNQ with Mn, Ru, Os, or Cu complex fragments which display evidence for a strong such interaction, i.e., an appreciable value delta in the formulation {(mu4-TCNXdelta-)[Mx+delta/4Ln]4}. Irreversibility of the first reduction of {(mu4-TCNB)[Fe(CO)2(C5H5)]4}(BF4)4 precluded spectroelectrochemical studies; however, the high-energy CN stretching frequencies and charge transfer absorptions of that TCNB analogue also confirm the exceptional position of the complexes {(mu4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4.

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Section: Resultsmentioning

confidence: 89%

Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄

et al. 2007

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References

2007

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Carbonyl complexes of manganese(I) with pyridazine: Synthesis and1H n.m.r. study

Bermejo

Ruiz

Vinaixa

1987

Transition Met Chem

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Syntheses, Mössbauer, and 1H NMR study of some cyclopentadienyliron carbonyl complexes with potentially bidentate amine ligands

Cited by 11 publications

References 18 publications

Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄

Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄

References

Carbonyl complexes of manganese(I) with pyridazine: Synthesis and1H n.m.r. study

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Syntheses, Mössbauer, and 1H NMR study of some cyclopentadienyliron carbonyl complexes with potentially bidentate amine ligands

Cited by 11 publications

References 18 publications

Tetranuclear Complexes of [Fe(CO)2(C5H5)]+ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ4-TCNX)[MLn]4

Tetranuclear Complexes of [Fe(CO)2(C5H5)]+ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ4-TCNX)[MLn]4

References

Carbonyl complexes of manganese(I) with pyridazine: Synthesis and1H n.m.r. study

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Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄

Tetranuclear Complexes of [Fe(CO)₂(C₅H₅)]⁺ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (μ₄-TCNX)[ML_n]₄