Electron-rich Fe(ii) and Fe(iii) organoiron σ-alkynyl complexes bearing a functional aryl group. Vibrational spectroscopic investigations of the substituent effect on the CC triple bond

Paul, Frédéric; Mevellec, Jean‐Yves; Lapinte, Claude

doi:10.1039/b108723c

Cited by 76 publications

(110 citation statements)

References 52 publications

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“…The IR spectra of the [Cp*(dppe)Fe II/III –C≡C–] acetylides display ν C≡C stretching modes at a frequency that is dependent on the oxidation state of the metal center and the electronic nature of the appended substituent. Its evolution has been qualitatively rationalized by a valence bond (VB) formalism 33,37–39. The IR spectra of solid‐state samples of [ 6 ‐ trans ][PF 6 ] n ( n = 0–3) are displayed in Figure 4, and the bands in the 2100–1600 cm –1 range are collected in Table 2, together with those previously reported for the reference compounds 7 [PF 6 ] n , 8 [PF 6 ] n , 9 [PF 6 ] n , and 10 [PF 6 ] n ( n = 0–3) for comparison.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Properties of a Mixed‐Valence Compound with Single‐Step Tunneling and Multiple‐Step Hopping Behavior

et al. 2014

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The organic precursor bis(trimethylsilylethynyl)TTFMe2 (3, TTF = tetrathiafulvalene) was prepared as a 1:1 mixture of the cis and trans isomers. Pure samples of 3‐cis and 3‐trans were obtained by crystallization and identified by XRD analysis. The treatment of pure 3‐trans and a 1:1 mixture of 3‐cis/trans with (i) potassium carbonate, (ii) the iron complex Cp*(dppe)FeCl [5, Cp* = η5‐C5Me5, dppe = 1,2‐bis(diphenylphosphanyl)ethane] in the presence of KPF6, and (iii) tBuOK provided Cp*(dppe)Fe–C≡C–TTFMe2–C≡C–Fe(dppe)Cp* as the pure geometric isomer 6‐trans (85 %) and as the 60:40 mixture 6‐cis/trans (63 %), respectively. The oxidation of 6‐trans with [(C5H5)2Fe]PF6 gave [6‐trans][PF6]n (n = 1–3). Visible, IR, near‐IR (NIR), and electron paramagnetic resonance (EPR) spectroscopy together with DFT data show that [6‐trans][PF6] is a class II mixed‐valence complex (Hab = 85 cm–1) in which the spin distribution depends on the conformation of the molecule. Intramolecular electron transfer occurs through single‐step tunneling and a multistep hoping mechanism. The triplet state is thermally accessible for [6‐trans][PF6]2.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Properties of a Mixed‐Valence Compound with Single‐Step Tunneling and Multiple‐Step Hopping Behavior

et al. 2014

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“…Paul, Lapinte, and co-workers have very recently reported on such oxidation-state-dependent Fermi coupling between CϵC and, presumably, CϪCϵ modes [44] for alkynyl complexes [Cp*(dppe)FeϪCϵCϪC 6 H 4 R-4] nϩ (n ϭ 0, 1, Fe II,III ). [45,46] Similar coupling between the CϵN stretch and the CϵNϪC bending modes of the isocyanide ligands in the triruthenium clusters [Ru 3 (NCR) 3 (µ 3 -O)(µ-CH 3 COO) 6 ] nϪ (n ϭ 0, 1) has recently been described by Kubiak et al [47] Since the band energy of the fundamental coupling with the CϭCϭC valence stretch is unknown, we adopt the center of the Fermi doublet as the energy of the unperturbed CϭCϭC stretch (and also of the other mode), but this is only an approximation. The alternative explanation of there being two distinct conformers with appreciably different ν(CϭCϭC) values cannot be discounted, but seems much Figure 8.…”

Section: Full Papermentioning

confidence: 98%

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

et al. 2003

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, L 2 = 2 PPh 3 or 1,1Ј-bis(diphenylphosphanyl)ferrocene (dppf), R = Ph or ferrocenyl] and their spectroscopic and electrochemical characteristics. Three of these compounds possess redox-active, ferrocenebased substituents or ligands − that are oxidized at lower potentials than the ruthenium center itself − attached either to the terminal carbon atom of the allenylidene ligand or to the ruthenium atom. The Fc/Ph-substituted complexes 3a and 3b provide unique examples of hindered rotation of the allenylidene substituent around the M=C bond. For 3a (L 2 = 2 PPh 3 ), two isomers differing in the orientation of the vertically aligned, unsymmetrically substituted allenylidene ligand are discernible even at 388 K. The dppf-substituted congener 3b has the allenylidene ligand in a horizontal orientation and exhibits a rotational barrier, as determined by dynamic 31 P NMR spectroscopy, of ∆G ϶ = 47 kJ/mol at T C = 238 K. The changes in the spectroscopic and electrochemical properties upon replacement of the PPh 3 by a dppf ligand and the Ph by an Fc moiety can be explained in terms of the bonding within these systems. These effects are attenuated when the ferrocene-based redox tags are oxidized, as shown by IR and

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“…In turn, the involvement of the alkynyl π system in stabilising the unpaired electron (or hole) can be conveniently assessed through the variation in the ν(CϵC) frequency as a function of molecular oxidation state. [15,20] Alkynyl complexes therefore offer a platform for the construction of open-shell systems in which the unpaired electron can be tuned across the spectrum of metal-localised to ligand-localised radicals. This variable electronic character, together with the approximately cylindrical distribution of π electron density along the CϵC axis, has also sparked immense interest in the electronic character (mixed valence or otherwise) of radicals derived from bimetallic complexes with alkynyl-bridging ligands.…”

Section: Introductionmentioning

confidence: 99%

Ligand Redox Non‐Innocence in Transition‐Metal σ‐Alkynyl and Related Complexes

Schauer

Low

2011

Eur J Inorg Chem

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Transition-metal σ-alkynyl complexes are valuable functional materials that have found application as sructural units in the assembly of polymetallic arrays and large molecular structures, reagents for the transfer, oligomerisation or functionalisation of alkynes, magnetic or optical materials and putative components for use in a future molecular-based electronics platform. Many σ-alkynyl complexes are redoxactive, undergoing facile oxidation (reduction) at moderate potentials to generate radical cations (anions) in which the

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Electron-rich Fe(ii) and Fe(iii) organoiron σ-alkynyl complexes bearing a functional aryl group. Vibrational spectroscopic investigations of the substituent effect on the CC triple bond

Cited by 76 publications

References 52 publications

Synthesis and Properties of a Mixed‐Valence Compound with Single‐Step Tunneling and Multiple‐Step Hopping Behavior

Synthesis and Properties of a Mixed‐Valence Compound with Single‐Step Tunneling and Multiple‐Step Hopping Behavior

(Allenylidene)ruthenium Complexes with Redox‐Active Substituents and Ligands

Ligand Redox Non‐Innocence in Transition‐Metal σ‐Alkynyl and Related Complexes

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