Crystal structure of 1,6-biferrocenyl-2,5-dicyanohexa-1,3,5-triene and intervalence transfer in the mixed-valence ion based on this structure

Amer, Sultan I.; Sadler, Garfield G.; Henry, Patrick M.; Ferguson, George; Ruhl, B. L.

doi:10.1021/ic00204a022

Cited by 18 publications

(13 citation statements)

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“…Thorough investigations on mixed-valent radical cations derived from homobimetallic ferrocenes and biferrocenes have significantly contributed to our present knowledge on how conformation, matrix effects, and ion pairing affect intramolecular electron-transfer rates and efficiencies. [59][60][61][62][63][64][65][66][67][68] Some ferrocenyl-π-bridge-ruthenium complexes have also been prepared and investigated with respect to intramolecular electron transfer in unsymmetrical mixed-valent systems. 56,[69][70][71][72][73][74][75][76][77][78] Here we report on heterobimetallic Ru(CHdCHFc)Cl-(CO)(P i Pr 3 ) 2 (1, Fc = (η 5 C 5 H 5 )Fe(η 5 -C 5 H 4 )) and its monoand dioxidized redox congeners (Chart 1).…”

Section: Introductionmentioning

confidence: 99%

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

et al. 2009

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Ru(CHdCHFc)Cl(CO)(P i Pr 3) 2 (Fc = ferrocenyl, (η 5-C 5 H 4)Fe(η 5-C 5 H 5)), 1, has been prepared by hydroruthenation of ethynylferrocene and characterized by NMR, IR, ESI-MS, and Moessbauer spectroscopy and by X-ray crystallography. Complex 1 features conjoined ferrocene and (vinyl)ruthenium redox sites and undergoes two consecutive reversible oxidations. Pure samples of crystalline, monooxidized 1 •+ have been prepared by chemical oxidation of 1 with the ferrocenium ion. Structural comparison with 1 reveals an increase of Fe-C and Fe-Cp centr. bond lengths and ring tilting of the Cp decks, as is typical of ferrocenium ions, but also a discernible lengthening of the Ru-C(CO) and Ru-P bonds and a shortening of the Ru-C(vinyl) bond upon oxidation. This supports the general idea of charge delocalization over both redox sites in 1 •+. Band shifts of the charge-sensitive IR labels (ν(CO) for Ru, ν(C-H, Cp) for Fc), the rather small g-anisotropy in the ESR spectrum of 1 •+ , and the results of quantum chemical calculations indicate that in solution the positive charge partly resides on the vinyl ruthenium moiety. Comparison of IR shifts in the solid state and in solution and the quadrupole splitting in the Moessbauer spectrum of powdered 1 •+ point to a larger extent of charge localization on the ferrocenyl site in solid samples. This is probably due to CH 3 3 3 F hydrogen bonding interactions between the cyclopentadienyl hydrogen atoms of the radical cations and the PF 6 counterions. Monooxidized 1 •+ displays low-energy electronic absorption bands at 1370 and 2150 nm. According to quantum chemical calculations, the underlying transitions are largely localized on the ferrocene part of the molecule with only little charge transfer into the vinyl ruthenium subunit. The second oxidation is more biased toward the (vinyl)ruthenium site.

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Section: Introductionmentioning

confidence: 99%

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

et al. 2009

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“…The mixed-valence states of conjugated ferrocene dimers have attracted considerable attention for decades because they are valuable examples affording intrinsic information regarding intramolecular electron-exchange reactions. − It has been shown that the chemical structure of the conjugated spacer group and its length dramatically affect the electronic interaction between the ferrocene units. Solvation effects on the electron exchange rate are also significant, and those for biferrocene and Fc−C⋮C−Fc have been analyzed by Powers and Meyer, by Blackbourn and Hupp, and by Weaver and co-workers 13 based on the Marcus−Hush theory .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Azo-Bridged Ferrocene Oligomers and a Polymer and Electrochemical and Optical Analysis of Internuclear Electronic Interactions in Their Mixed-Valence States

et al. 1999

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New azo-bridged ferrocene trimers, Fc-Fc'-N=N-Fc (2) and Fc-N=N-Fc'-N=N-Fc (3), where Fc and Fc' refer to (eta(5)-C(5)H(5))Fe(eta(5)-C(5)H(4)-) and Fe(eta(5)-C(5)H(4)-)(2), respectively, were obtained in the reaction of a mixture of lithioferrocene and 1,1'-dilithioferrocene with N(2)O. X-ray crystallography of azoferrocene (1) has determined that the Fe-Fe distance is 6.80 Å in the trans form. Cyclic voltammograms of 3 in aprotic solvents such as CH(2)Cl(2) or THF exhibit reversible 2e(-) and 1e(-) oxidation waves, indicating that the positive charge in the monocation is localized mostly on the terminal ferrocene unit (correspondingly, Fc(+)-N(2)-Fc'-N(2)-Fc) due to a strong electron-withdrawing effect of the azo group. This charge distribution in the mixed-valence state is supported by the characteristics of intervalence-transfer (IT) bands. An asymmetrical complex, 2, undergoes a three-step 1e(-) oxidation, and the two mixed-valence forms can be roughly expressed as Fc(+)-Fc'-N(2)-Fc and Fc(+)-Fc'-N(2)-Fc(+). The redox potentials and IT band characteristics of 1(+), 2(+), and 2(2+) depend markedly on the solvent. The solvent effect of the IT band on nu(max) cannot be interpreted only by the parameters in the Marcus-Hush theory, indicating that the nature of the solvent as donor or acceptor should be taken into account in the electron-exchange process in the mixed-valence states. More donating solvent affords higher IT and LMCT energy, indicating the hole-transfer mechanism. The reaction of 1,1'-dilithioferrocene and N(2)O gives a polymer composed of [-(Fc'-N=N-Fc')(0.6)-(Fc'-Fc')(0.4)-](n)().

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“…Binuclear complexes with metallocene termini have been extensively investigated because of their great stability. In particular, ferrocene derivatives − have been studied intensively as mixed-valence complexes, since ferrocene is stable in both the neutral and oxidized forms − because ruthenocene shows an irreversible two-electron oxidation process which hinders understanding.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Redox Behavior of Ruthenium(II) 2,3,4,5-Tetramethylruthenocenylacetylide and Related Complexes. Formation of μ-η⁶:η¹-[(Cyclopentadienylidene)ethylidene]diruthenium Complexes Containing a Strong Metal−Metal Interaction

1999

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1-Ethynyl-2,3,4,5-tetramethylruthenocene was prepared by the reaction of 1-formyl-2,3,4,5-tetramethylruthenocene with trimethylsilyldiazomethyllithium and also by the reaction of 1-(2‘,2‘-dichlorovinyl)-2,3,4,5-tetramethylruthenocene, which was obtained from the reaction of 1-formyl-2,3,4,5-tetramethylruthenocene with lithium dichloromethyldiethylphosphonate and tert-butyllithium in good yield. 1-Ethynyl-2,3,4,5-tetramethylruthenocene reacted with RuClP 2L (P 2 = 2 PPh3 or dppe; L = η-C5H5, η-C5Me5, or η5-C9H7) in the presence of NH4PF6 or AgBF4, followed by the column chromatography on deactivated Al2O3, to give Ru(C⋮CRc‘)P 2L in moderate or good yield. Ru(C⋮CRc)P 2(η5-C9H7) and Ru(C⋮CRc*)P 2(η5-C9H7) were similarly prepared (Rc, Rc‘, and Rc* are ruthenocenyl, 2,3,4,5-tetramethylruthenocenyl, and 1‘,2‘,3‘,4‘,5‘-pentamethylruthenocenyl, respectively). The structures of Ru(C⋮CRc‘)(dppe)(PPh3)2(η-C5H5), Ru(C⋮CRc)(dppe)(η5-C9H7), and Ru(C⋮CRc‘)(dppe)(η5-C9H7) were determined by X-ray analysis. Cyclic voltammetry of the acetylide complexes showed two well-separated quasi-reversible waves. Chemical oxidation of ruthenium(II) 2,3,4,5-tetramethylruthenocenylacetylide complexes gave products whose stability was dependent on the ligand on the Ru(II) moiety. The 13C NMR spectrum of the oxidized species isolated as stable crystals confirmed the structural rearrangement of the bridging acetylide ligand to a μ-η6:η1-[(cyclopentadienylidene)ethylidene] ligand. The structure of [(η-C5H5)Ru(μ-η6:η1-C5Me4CC)Ru(dppe)(η5-C5Me5)](BF4)2 was determined by X-ray analysis.

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Crystal structure of 1,6-biferrocenyl-2,5-dicyanohexa-1,3,5-triene and intervalence transfer in the mixed-valence ion based on this structure

Cited by 18 publications

References 0 publications

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Synthesis of Azo-Bridged Ferrocene Oligomers and a Polymer and Electrochemical and Optical Analysis of Internuclear Electronic Interactions in Their Mixed-Valence States

Synthesis and Redox Behavior of Ruthenium(II) 2,3,4,5-Tetramethylruthenocenylacetylide and Related Complexes. Formation of μ-η⁶:η¹-[(Cyclopentadienylidene)ethylidene]diruthenium Complexes Containing a Strong Metal−Metal Interaction

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Crystal structure of 1,6-biferrocenyl-2,5-dicyanohexa-1,3,5-triene and intervalence transfer in the mixed-valence ion based on this structure

Cited by 18 publications

References 0 publications

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PiPr3)2 System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PiPr3)2 System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Synthesis of Azo-Bridged Ferrocene Oligomers and a Polymer and Electrochemical and Optical Analysis of Internuclear Electronic Interactions in Their Mixed-Valence States

Synthesis and Redox Behavior of Ruthenium(II) 2,3,4,5-Tetramethylruthenocenylacetylide and Related Complexes. Formation of μ-η6:η1-[(Cyclopentadienylidene)ethylidene]diruthenium Complexes Containing a Strong Metal−Metal Interaction

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Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Charge Delocalization in a Heterobimetallic Ferrocene−(Vinyl)Ru(CO)Cl(PⁱPr₃)₂ System†Dedicated to Prof. Dr. Helmut Werner on the occasion of his 75th birthday

Synthesis and Redox Behavior of Ruthenium(II) 2,3,4,5-Tetramethylruthenocenylacetylide and Related Complexes. Formation of μ-η⁶:η¹-[(Cyclopentadienylidene)ethylidene]diruthenium Complexes Containing a Strong Metal−Metal Interaction