Structural Changes Accompanying Metal Complex Electrode Reactions

Geiger, William E.

doi:10.1002/9780470166345.ch6

Cited by 132 publications

(12 citation statements)

References 152 publications

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“…This experiment suffered, however, from severely absorptive behavior and particularly problematic electrode passivation. Nevertheless, these results support that the 9 / 9 – redox system and the electroactive product, which is generated from 9 – , constitute an overall (at least partially) reversible redox system, which obeys an overall “square scheme” mechanism …”

Section: Resultssupporting

confidence: 57%

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

et al. 2021

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In this contribution, we revisit the neglected and forgotten cationic, air-stable, 18-valence electron, heteroleptic sandwich complex (cycloheptatrienyl)(cyclopentadienyl)manganese, which was reported independently by Fischer and by Pauson about 50 years ago. Using advanced high-power LED photochemical synthesis, an expedient rapid access to the parent complex and to functionalized derivatives with alkyl, carboxymethyl, bromo, and amino substituents was developed. A thorough study of these “tromancenium” salts by a range of spectroscopic techniques ( 1 H/ 13 C/ 55 Mn-NMR, IR, UV–vis, HRMS, XRD, XPS, EPR), cyclic voltammetry (CV), and quantum chemical calculations (DFT) shows that these manganese sandwich complexes are unique metallocenes with quite different chemical and physical properties in comparison to those of isoelectronic cobaltocenium salts or (cycloheptatrienyl)(cyclopentadienyl) sandwich complexes of the early transition metals. Electrochemically, all tromancenium ions undergo a chemically partially reversible oxidation and a chemically irreversible reduction at half-wave or peak potentials that respond to the substituents at the Cp deck. As exemplarily shown for the parent tromancenium ion, the product generated during the irreversible reduction process reverts at least partially to the starting material upon reoxidation. Quantum-chemical calculations of the parent tromancenium salt indicate that metal–ligand bonding is distinctly weaker for the cycloheptatrienyl ligand in comparison to that of the cyclopentadienyl ligand. Both the HOMO and the LUMO are metal and cycloheptatrienyl-ligand centered, indicating that chemical reactions will occur either metal-based or at the seven-membered ring, but not on the cyclopentadienyl ligand.

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Section: Resultssupporting

confidence: 57%

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

et al. 2021

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“…Several experimental and theoretical studies have previously established that the one-electron oxidation of diiron dithiolate analogues of 1 and 2 induces a geometry change that produces a cation with an inverted pyramid about one Fe center, the so-called rotated state. − The structure change may follow the electron transfer (EC mechanism) or be concerted with it (quasi-reversible process, QR). − The experimental study of the first oxidation of 1 did not allow us to discriminate between the above possibilities, since the increase of the scan rate ( v ≤ 20 V s –1 ) only results in an increase of the peak separation Δ E p , as already noted for 2 . Digital CV simulations of the oxidation of 1 according to either an EC or a QR mechanism suggest that both are consistent with the experimental data (Supporting Information, Figure S1) .…”

Section: Resultsmentioning

confidence: 99%

“…The fact that a single two-electron transfer is observed in neat MeCN is in accord with the negative shift of the potential (see E 2 (L′) in Scheme ) in CH 2 Cl 2 upon increasing the concentration of MeCN. The different solvent dependences of the potentials of the dication/cation couple may also contribute to the occurrence of two separate oxidation steps in dichloromethane. ,,− …”

Section: Resultsmentioning

confidence: 99%

Electrochemical and Theoretical Studies of the Impact of the Chelating Ligand on the Reactivity of [Fe₂(CO)₄(κ²-LL)(μ-pdt)]⁺ Complexes with Different Substrates (LL = I_Me-CH₂-I_Me, dppe; I_Me = 1-Methylimidazol-2-ylidene)

et al. 2012

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“…In general, the expected redox waves that are known for the monomers are found in the CVs of the metallocopolymers . In spite of the high molecular weights of all the metallopolymers, the redox waves are chemically reversible; − i.e., i a and i c are relatively close, although rarely identical intensities. A strong characteristic in all the CVs for the redox centers of the copolymers is the weak Ep a – Ep c value, signifying strong adsorption onto the electrode due to the large molecular weight and important solubility changes upon variations of large change of charge state.…”

Section: Results and Discussionmentioning

confidence: 96%

“…Cyclic voltammetry of the Fc + /Fc, ,− Fc* + /Fc*, , and CcX/Cc + /Cc redox systems is well-known. In general, the expected redox waves that are known for the monomers are found in the CVs of the metallocopolymers .…”

Section: Results and Discussionmentioning

confidence: 99%

Living ROMP Syntheses and Redox Properties of Triblock Metallocopolymer Redox Cascades

Ciganda

Castel

et al. 2016

Macromolecules

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A number of reports have described the synthesis by ring-opening metathesis polymerization (ROMP) of diblock metallopolymers containing ferrocene and organocobalt complexes using the very efficient Grubb's thirdgeneration metathesis catalyst. Here the first triblock metallocopolymers are reported using this catalyst with ferrocenyl, pentamethylferrocenyl, and cobalticenyl groups in the side chains of a polynorbornene backbone. Among the six possible synthetic schemes for the successive ROMP reactions of the blocks, two of them have been successfully conducted with adequate characterization using the endgroup analysis, MALDI-TOF mass spectroscopy, and Bard−Anson's electrochemical method. The cyclic voltammetry studies showed that the integrity of reversible redox systems was preserved in cascades of heterogeneous electron transfers in both metallocopolymers with significant adsorption and electrostatic effects. This research paves the way for the design and synthesis of multiblock metallocopolymers offering access to multiproperty nanomaterials. ■ INTRODUCTIONRedox cascades are involved in various area of synthesis, 1 medicine, 2,3 biochemistry, 4,5 and nanomaterials, 6−10 as for instance total synthesis, 1 physiological functions and human diseases 2 including oxidative-stress-induced cancer, 2b regulation of gene expression, 3 signaling in plants, 4 biocatalysis, 5 dendrimer 6,7 and fullerene 8 electrochemistry, 6−8 sensing and catalysis, 7 photoreduction of CO, 2,9 gold nanocluster charging, 10 and catalysis by metal clusters 11 with the assistance of metal−oxo cluster cocatalysis. 11b Late-transition-metal sandwich complexes 12 also provide multiple redox changes 13 given their delocalized electronic structures 14 that allow the stabilization of several oxidation states. In particular, disandwich electron-reservoir complexes containing delocalized polyaromatic ligands provide multielectron redox cascades 15 including several mixed valence species. 16 Metal-containing polymers are a rich field concerning redox properties toward materials applications. 17 Thus, another approach to molecular electronreservoir systems providing redox cascades is now proposed with metallopolymers synthesized by living ring-opening metathesis polymerization (ROMP) that allows the introduction of several metallopolymer blocks. 18 Transition-metal sandwich-containing polymers have been abundantly published, 19 and recently a number of reports have appeared with ferrocenyl, 20 pentamethylferrocenyl, 21 and cobaltocenyl 22 units from our group 20−22 and others 23,24 using the very efficient and practical third-generation Grubbs' catalyst 1 for living ROMP. 18d,25 Here we report the ROMP syntheses and electrochemical properties of the first triblock metallopolymers containing three distinct redox-active metal-sandwich moieties in the side chains, namely, the ferrocenyl (Fc), pentamethylferrocenyl (Fc*), and cobalticenyl hexafluorophosphate (CcX) groups. ■ RESULTS AND DISCUSSIONIn the three norbornene derivatives 2, 3, and 4, the metal...

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Structural Changes Accompanying Metal Complex Electrode Reactions

Cited by 132 publications

References 152 publications

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Electrochemical and Theoretical Studies of the Impact of the Chelating Ligand on the Reactivity of [Fe₂(CO)₄(κ²-LL)(μ-pdt)]⁺ Complexes with Different Substrates (LL = I_Me-CH₂-I_Me, dppe; I_Me = 1-Methylimidazol-2-ylidene)

Living ROMP Syntheses and Redox Properties of Triblock Metallocopolymer Redox Cascades

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Structural Changes Accompanying Metal Complex Electrode Reactions

Cited by 132 publications

References 152 publications

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Electrochemical and Theoretical Studies of the Impact of the Chelating Ligand on the Reactivity of [Fe2(CO)4(κ2-LL)(μ-pdt)]+ Complexes with Different Substrates (LL = IMe-CH2-IMe, dppe; IMe = 1-Methylimidazol-2-ylidene)

Living ROMP Syntheses and Redox Properties of Triblock Metallocopolymer Redox Cascades

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Electrochemical and Theoretical Studies of the Impact of the Chelating Ligand on the Reactivity of [Fe₂(CO)₄(κ²-LL)(μ-pdt)]⁺ Complexes with Different Substrates (LL = I_Me-CH₂-I_Me, dppe; I_Me = 1-Methylimidazol-2-ylidene)