%0 Journal Article %1 Maity.2007 %A Maity, Amarendra N. %A Schwederski, Brigitte %A Sarkar, Biprajit %A Zalis, Stanislav %A Fiedler, Jan %A Kar, Sanjib %A Lahiri, Goutam K. %A Duboc, Carole %A Grunert, Matthias %A Guetlich, Philipp %A Kaim, Wolfgang. %D 2007 %J Inorganic Chemistry %K DFT EPR cyclopentadienyl dicarbonyl electrochem electron geometry iron redox structure tetracyanoethene tetracyanoquinodimethane transfer transfer;Moessbauer transfer;electronic transfer;optimized %N 18 %P 7312--7320 %R 10.1021/ic062253k %T Tetranuclear Complexes of Fe(CO)2(C5H5)+ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (m4-TCNX)MLn4 %V 46 %X (μ4-TCNX)Fe(CO)2(C5H5)4(BF4)4 were prepd. 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 redn. potentials \textgreater+0.3 V vs. ferrocenium/ferrocene, the tetranuclear complex of TCNB exhibits a significantly more neg. redn. potential at $\sim$-1.0 V. Even for the complexes with strongly p-accepting TCNE and TCNQ, the very pos. redn. potentials, the unusually high nitrile stretching frequencies \textgreater2235 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°)(FeII)4 formulation of oxidn. states as caused by orthogonality between the metal-centered HOMO and the p* LUMO of TCNX. Mossbauer spectroscopy confirms the low-spin Fe(II) state, and DFT calcns. suggest coplanar TCNE and TCNQ bridging ligands in the complex tetracations. One-electron redn. 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 \textless2, in addn. to a negligible g anisotropy of frozen solns. at frequencies up to 285 GHz and also through an unusually well-resolved soln. X band EPR spectrum of (μ4-TCNE)Fe(CO)2(C5H5)43+ which shows four equiv. Fe(CO)2(C5H5)+ moieties through 57Fe and 13C(CO) hyperfine coupling in nonenriched material. DFT calcns. reproduce the exptl. EPR data. A survey of discrete TCNE and TCNQ complexes (m4-TCNX)(MLn)4 exhibits a dichotomy between the systems (μ4-TCNX)Fe(CO)2(C5H5)44+ and (μ4-TCNQ)Re(CO)3(bpy)44+ with their negligible metal-to-ligand electron transfer and several other compds. 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 d in the formulation (μ4-TCNXδ-)Mx+δ/4Ln4. Irreversibility of the 1st redn. of (μ4-TCNB)Fe(CO)2(C5H5)4(BF4)4 precluded spectroelectrochem. studies; however, the high-energy CN stretching frequencies and charge transfer absorptions of that TCNB analog also confirm the exceptional position of (μ4-TCNX)Fe(CO)2(C5H5)4(BF4)4. on SciFinder(R)

@article{Maity.2007, abstract = {{(μ4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4 were prepd. 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 redn. potentials {\textgreater}+0.3 V vs. ferrocenium/ferrocene, the tetranuclear complex of TCNB exhibits a significantly more neg. redn. potential at $\sim$-1.0 V. Even for the complexes with strongly \textgreek{p}-accepting TCNE and TCNQ, the very pos. redn. potentials, the unusually high nitrile stretching frequencies {\textgreater}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°)(FeII)4 formulation of oxidn. states as caused by orthogonality between the metal-centered HOMO and the \textgreek{p}* LUMO of TCNX. Mossbauer spectroscopy confirms the low-spin Fe(II) state, and DFT calcns. suggest coplanar TCNE and TCNQ bridging ligands in the complex tetracations. One-electron redn. 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 {\textless}2, in addn. to a negligible g anisotropy of frozen solns. at frequencies up to 285 GHz and also through an unusually well-resolved soln. X band EPR spectrum of {(μ4-TCNE)[Fe(CO)2(C5H5)]4}3+ which shows four equiv. [Fe(CO)2(C5H5)]+ moieties through 57Fe and 13C(CO) hyperfine coupling in nonenriched material. DFT calcns. reproduce the exptl. EPR data. A survey of discrete TCNE and TCNQ complexes [(\textgreek{m}4-TCNX)(MLn)4] exhibits a dichotomy between the systems {(μ4-TCNX)[Fe(CO)2(C5H5)]4}4+ and {(μ4-TCNQ)[Re(CO)3(bpy)]4}4+ with their negligible metal-to-ligand electron transfer and several other compds. 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 \textgreek{d} in the formulation {(μ4-TCNXδ-)[Mx+δ/4Ln]4}. Irreversibility of the 1st redn. of {(μ4-TCNB)[Fe(CO)2(C5H5)]4}(BF4)4 precluded spectroelectrochem. studies; however, the high-energy CN stretching frequencies and charge transfer absorptions of that TCNB analog also confirm the exceptional position of {(μ4-TCNX)[Fe(CO)2(C5H5)]4}(BF4)4. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Maity, Amarendra N. and Schwederski, Brigitte and Sarkar, Biprajit and Zalis, Stanislav and Fiedler, Jan and Kar, Sanjib and Lahiri, Goutam K. and Duboc, Carole and Grunert, Matthias and Guetlich, Philipp and Kaim, Wolfgang.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2c2d9f8d10c4e91bd2ae47cd61dba3dff/huebleriac}, doi = {10.1021/ic062253k}, interhash = {0d6d985f3a7d15cf424c24b7e9f26385}, intrahash = {c2d9f8d10c4e91bd2ae47cd61dba3dff}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {DFT EPR cyclopentadienyl dicarbonyl electrochem electron geometry iron redox structure tetracyanoethene tetracyanoquinodimethane transfer transfer;Moessbauer transfer;electronic transfer;optimized}, number = 18, pages = {7312--7320}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Tetranuclear Complexes of [Fe(CO)2(C5H5)]+ with TCNX Ligands (TCNX = TCNE, TCNQ, TCNB): Intramolecular Electron Transfer Alternatives in Compounds (\textgreek{m}4-TCNX)[MLn]4}, volume = 46, year = 2007 }