A redox-switchable ring-closing metathesis catalyst

Lastovickova, Dominika N.; Teator, Aaron J.; Shao, Huiling; Liu, Peng; Bielawski, Christopher W.

doi:10.1039/c7qi00018a

Cited by 21 publications

(17 citation statements)

References 97 publications

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“…After 10 min, the current began to decrease, which indicated that the electrolysis was becoming limited by mass transfer and reaching saturation. A color change from light green to brown, consistent with the conversion 1 → 1 red , 51 accompanied the change in current. After 20 min, the current approached zero, consistent with consumption of the neutral complex.…”

Section: Resultsmentioning

confidence: 68%

“…These observations are in concordance with results that were obtained when redox reagents were used and reflect the high fidelity of the electrochemical process of 1. 51,52 Inspection of the electrolysis data revealed that the diffusioncontrolled reduction processes appeared to occur slightly more quickly than the subsequent oxidations. To ascertain the origin of this observation, diffusion coefficients were calculated using the Randles−Sevcik equation.…”

Section: Resultsmentioning

confidence: 99%

“…The ratio of the corresponding rate constants, k 1 /k 1,red , was calculated to be 6.5; for comparison, a ratio of 6.7 was measured for analogous reactions that were performed using chemical oxidants and Organometallics pubs.acs.org/Organometallics Article reductants to effect the redox chemistry. 51 The different catalytic activities that were observed can be attributed to the N-heterocyclic carbene ligand, which upon reduction stabilizes the ruthenacyclobutane resting state of the catalytic cycle in a manner that suppresses retro-[2 + 2] cycloadditions and thus decreases the rate of the RCM reaction. 67 The catalytic activity displayed by 1 after a full electrolysis cycle (reduction and oxidation) was also assessed.…”

Section: Resultsmentioning

confidence: 99%

“…The phenomenon was attributed to the relative instability of the alkylidene or methylidene propagating species, 68 which may undergo premature decomposition under the reductive or oxidative conditions utilized. 51 After demonstrating that BE may be used to control RCM reactions, we directed our attention toward controlling the ROMP of 1,5-cyclooctadiene (COD). Efforts began by evaluating the activities displayed by the neutral and reduced forms of the complex (1 and 1 red , respectively).…”

Section: Resultsmentioning

confidence: 99%

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Potentiostatically Controlled Olefin Metathesis

2020

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A Ru(II) complex supported by an N-heterocyclic carbene annulated to a redox-active naphthoquinone (NQ) was interrogated using a range of potentiodynamic and potentiostatic electrochemical techniques. The complex exhibited two redox processes, one of which was attributed to the Ru(II)|Ru(III) couple (E 1/2 = +1.10 V vs a saturated calomel electrode) and the other to the NQ|NQ − couple (E 1/2 = −0.62 V). Using potentiostatic coulometry or bulk electrolysis, the application of a fixed negative potential (−0.95 V) to electrodes placed in a dichloromethane solution containing the complex resulted in a reduction reaction. The complex was quantitatively reduced within minutes, as determined by coulometry, and subsequently oxidized to its initial, neutral form through the application of a relatively positive potential (+0.34 V) over similar periods of time. The interconversion process was found to be reversible and used to modulate a series of ring-closing metathesis and ring-opening metathesis polymerization reactions. While relatively high activities were observed when the neutral form of the catalyst was employed, the reaction rates were attenuated upon in situ, potentiostatic reduction. Toggling between relatively negative or positive potentials enabled the aforementioned olefin metathesis reactions to be switched between fast and slow states.

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Section: Resultsmentioning

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Potentiostatically Controlled Olefin Metathesis

2020

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“…[76][77][78] Earlier this year, we reported a means to remotely control monomer selectivity in ROMP reactions. 79,80 Substituting the NHC ligand in the G3 complex with an analogue that featured a redox-active quinone unit provided a handle through which catalytic activity could be modulated (Fig. 13, 28).…”

Section: Redox-activated Catalystsmentioning

confidence: 99%

Remote control grubbs catalysts that modulate ring‐opening metathesis polymerizations

Teator

Bielawski

2017

J. Polym. Sci. Part A: Polym. Chem.

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A broad range of stimuli, including light, heat, mechanical force, or changes in chemical potential, may be used to toggle Ru-based catalysts between multiple distinct states of activity. Catalysts with such features offer a means to temporallyand, in some cases, spatially-control a variety of polymerizations, and thus should facilitate access to synthetic macromolecular materials with tunable structures and properties. Due to the intrinsic versatility and robustness of the Grubbs-type catalyst platforms, numerous remotely controlled ring-opening metathesis polymerizations have been introduced. Herein, selected examples of stimuli-responsive catalysts that have been recently used for such purposes are surveyed and discussed. Perspectives on potential opportunities for development and growth as well as an outlook for the field are also provided.

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Redox‐Switchable Catalysis

Regenauer

Doll

Roşca

2022

Encyclopedia of Inorganic and Bioinorganic Chemistry

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The ability to control catalytic properties, such as selectivity and rate during the reaction, represents an attractive tool which can potentially deliver the synthesis of specialized products from a large pool of building blocks. This can be achieved by the incorporation of an on / off switch into the backbone of (pre‐)catalysts. The electronic or solubility properties of the switch can be then reversibly modified through the action of external triggers, a process which in turn modulates the catalytic activity. Incorporation of switches that can be reversibly reduced or oxidized represents one of the most versatile methods for controlling the catalytic activity in situ. This article describes the current state of research in the field of redox‐switchable catalysis, with a focus on homogenous metal‐mediated processes. The first part presents an overview of the types of redox switches and of the methods employed for delivering the redox stimuli. The second part then focuses on the catalytic transformations which can be controlled in this fashion, which include polymerization catalysis, metathesis, hydroelementation, and other catalytic reactions for the synthesis of fine chemicals.

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A redox-switchable ring-closing metathesis catalyst

Abstract: A ring-closing metathesis catalyst was arrested upon reduction of a redox-active ligand; subsequent oxidation restored catalytic activity.

Cited by 21 publications

References 97 publications

Potentiostatically Controlled Olefin Metathesis

Potentiostatically Controlled Olefin Metathesis

Remote control grubbs catalysts that modulate ring‐opening metathesis polymerizations

Redox‐Switchable Catalysis

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