Structural consequences of electron transfer reactions. 21. Structural changes coupled to two-electron-transfer reactions: oxidation mechanism of pseudo-triple-decker complexes of cobalt and rhodium

Edwin, Joseph; Geiger, William E.

doi:10.1021/ja00176a004

Cited by 32 publications

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“…Complexes 7 a – 7 c , 8 a , and 8 b were oxidized in a chemically reversible process without an observable radical cation intermediate, although this redox reaction is electrochemically irreversible. Plausibly it can take place through the process shown in Scheme for complex 7 b , which is similar to the square scheme proposed by Geiger 16a. 24 The process is composed of two simultaneous one‐electron oxidations followed by a rapid chemical transformation (the structural rearrangement).…”

Section: Resultssupporting

confidence: 56%

Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Satô

Nagata

Tanemura

et al. 2004

Chemistry A European J

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Ruthenocene-terminated butadienes and hexatrienes were prepared by the Wittig reaction of 3-ruthenocenyl-2-propenals with ruthenocenylmethylphosphonium salts and the Mukaiyama coupling of the propenals, respectively. Cyclic voltammetry of these complexes indicated that they were involved in a stable two-electron redox process. The oxidation potentials for ruthenocene-terminated oligoenes shifted progressively to lower potential with the increasing CH==CH units as follows: Rc--Rc (0.32 V)>RcCH==CHRc (+0.09 V)>Rc(CH==CH)(2)Rc (-0.06 V)>Rc(CH==CH)(3)Rc (-0.07 V), (Rc=ruthenocene). The tendency is in remarkable contrast to that in the successive one-electron redox process. These complexes were chemically oxidized to give stable crystalline solids, whose structures were confirmed by NMR spectroscopy and X-ray analysis to be oligoene analogues of a bis(fulvene) complex, for example, [(eta(5)-C(5)Me(5))Ru[mu(2)-eta(6):eta(6)-C(5)H(4)CH(CH==CH)(n)CHC(5)H(4)]Ru(eta(5)-C(5)Me(5))](2+) (n=1 or 2). The DFT calculation of the two-electron-oxidized species reproduced well the fulvene-complex structure for the ruthenocene moieties. Since both the neutral and oxidized species are stable and chemically reversible, this redox system may be serviceable as a two-electron version of the ferrocene one-electron redox system.

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Section: Resultssupporting

confidence: 56%

Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Satô

Nagata

Tanemura

et al. 2004

Chemistry A European J

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“…Electron-transfer reactions with first-row transition metals typically follow one-electron (1e – ) pathways. Therefore, many synthetic first-row metal complexes that have shown multielectron reactivity incorporate multiple metal centers, where each is oxidized/reduced by 1e – . − For complexes that achieve multielectron redox chemistry at monometallic centers, however, structural changes around the metal center and/or noninnocent ligands have been utilized to force a multielectron pathway over single electron transfer. − In these examples, the 1e – redox potentials associated with the metal center are shifted from their normal ordering to a condition known as potential inversion …”

Section: Introductionmentioning

confidence: 99%

Influence of Pyridine on the Multielectron Redox Cycle of Nickel Diethyldithiocarbamate

Richburg

Farnum

2019

Inorg. Chem.

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Two-electron (2e − )-transfer reactions for monometallic complexes of first-row transition metals are uncommon because of the tendency of these metals to proceed through sequential one-electron (1e − )-transfer pathways. For this chemistry to be observed, structural changes upon electron transfer are often needed to shift the 1e − redox potentials to a condition of potential inversion where 2e − transfer becomes favorable. Nickel(II) dithiocarbamate complexes take advantage of these conditions to drive 2e − oxidation from Ni II to Ni IV . Here, we have studied the electrochemistry of Ni II (dtc) 2 , where dtc − is N,N-diethyldithiocarbamate in an acetonitrile solvent as a function of the scan rate and added pyridine to gain further insight into the mechanism for its 2e − oxidation to [Ni IV (dtc) 3 ] + . The scan rate dependence revealed evidence for an ECE mechanism in which the chemical step constituted ligand exchange between [Ni III (dtc) 2 ] + and Ni II (dtc) 2 . A pseudo-first-order rate constant for this reaction of 34 s −1 was obtained at 1 mM Ni II (dtc) 2 . The addition of pyridine to the electrolyte solution showed pronounced changes to the cyclic voltammetry (CV) that were consistent with the formation of a pyridine-bound Ni III complex, [Ni III (dtc) 2 (py) 2 ] + , which was stable at high scan rates but decomposed to [Ni IV (dtc) 3 ] + at low scan rates. The observed decomposition rate constant was well modeled with two parallel decay pathways, one through the dipyridine [Ni III (dtc) 2 (py) 2 ] + and another through a monopyridine [Ni III (dtc) 2 py] + . Overall, these data point to a mechanism for oxidation from Ni II (dtc) 2 to [Ni IV (dtc) 3 ] + that proceeds through an undercoordinated [Ni III (dtc) 2 ] + complex, which can be trapped on the time scale of CV experiments using pyridine ligands. These studies provide insight into how we may be able to control 1e − versus 2e − redox chemistry using the coordination environment and nickel oxidation state.

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“…This conclusion is indicated by the fact that a current plateau of 3.7 μA was measured for 1 prior to bulk electrolysis, but only 2.7 μA was observed for 1 2+ after the anodic reaction. Considerably reduced diffusion coefficients have been found previously for dications in CH 2 Cl 2 compared to their neutral precursors. ,− …”

Section: Resultsmentioning

confidence: 71%

Electrochemical and Structural Characterization ofcis- andtrans-[Cp(CO)Ru(μ-As(C₆H₅)₂)]₂, Isomers That Undergo Two-Electron-Transfer Oxidations

et al. 1998

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The structures and oxidations of the cis and trans isomers of the doubly bridged dinuclear species [Cp(CO)Ru(μ-AsPh2)]2 (Ph = C6H5) have been studied by X-ray crystallography, electrochemistry, and IR and NMR spectroscopies. Each complex oxidizes in a single two-electron voltammetric process, the E 1/2 values being −0.36 V for the cis isomer (1) and −0.30 V for the trans isomer (2) in CH2Cl2/0.1 M [NBu4][PF6] (referenced to ferrocene). These are apparently the first comparative redox potentials published for cis and trans isomers of bridged dinuclear organometallic complexes. Oxidation of 1 to 1 2+ was cleanly accomplished either by electrolysis or by oxidation of 1 by 2 equiv of ferrocenium, allowing isolation of the dication. The split carbonyl absorptions in the IR spectra of 1 2+ (νCO = 2032, 2050 cm-1) are consistent with formation of a Ru−Ru bond in the oxidation reaction. The electrode reaction 1/1 + + e- is much slower than the reaction 1 +/1 2+ + e-, implying that the metal−metal bond is formed in the former process. This conclusion is supported by the observation that the inner-sphere activation barrier, ΔG ⧧, is about 8.5 kcal/mol, close to that (∼10 kcal/mol) estimated for a one-electron oxidation involving formation and cleavage of a Ru−Ru bond. The electron-transfer (ET) activation barrier is higher in these Ru complexes than in analogous Fe complexes, which are known to undergo large ET-induced changes in metal−metal bond lengths, most likely because M−M bond strengths are larger when M = Ru than when M = Fe.

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Structural consequences of electron transfer reactions. 21. Structural changes coupled to two-electron-transfer reactions: oxidation mechanism of pseudo-triple-decker complexes of cobalt and rhodium

Cited by 32 publications

References 0 publications

Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Influence of Pyridine on the Multielectron Redox Cycle of Nickel Diethyldithiocarbamate

Electrochemical and Structural Characterization ofcis- andtrans-[Cp(CO)Ru(μ-As(C₆H₅)₂)]₂, Isomers That Undergo Two-Electron-Transfer Oxidations

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Structural consequences of electron transfer reactions. 21. Structural changes coupled to two-electron-transfer reactions: oxidation mechanism of pseudo-triple-decker complexes of cobalt and rhodium

Cited by 32 publications

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Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Synthesis and Redox Behavior of Ruthenocene‐Terminated Oligoenes: Characteristic and Stable Two‐Electron Redox System and Lower Potential Shift of the Two‐Electron Oxidation Wave with Elongating Conjugation

Influence of Pyridine on the Multielectron Redox Cycle of Nickel Diethyldithiocarbamate

Electrochemical and Structural Characterization ofcis- andtrans-[Cp(CO)Ru(μ-As(C6H5)2)]2, Isomers That Undergo Two-Electron-Transfer Oxidations

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Electrochemical and Structural Characterization ofcis- andtrans-[Cp(CO)Ru(μ-As(C₆H₅)₂)]₂, Isomers That Undergo Two-Electron-Transfer Oxidations