Hydrogen-Atom Noninnocence of a Tridentate [SNS] Pincer Ligand

Rosenkoetter, Kyle E.; Wojnar, Michael K.; Charette, Bronte J.; Heyduk, Alan F.

doi:10.1021/acs.inorgchem.8b00618

Cited by 34 publications

(41 citation statements)

References 60 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The H 2 evolution pathways of, e. g., pincer, thiosemicarbazone, and thiolate complexes are known to involve the redox‐active scaffold. Proton relay sites and redox‐active ligands are proposed to significantly enhance the kinetics of H 2 formation and decrease the HER overpotentials of metal complexes . However, a redox non‐innocent coordination environment also may result in non‐productive pathways .…”

Section: Introductionmentioning

confidence: 99%

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

et al. 2019

View full text Add to dashboard Cite

H2 is a promising fuel for sustainable energy conversion and storage. The development of effective earth abundant H2 evolution catalysts is integral to advancing hydrogen‐based technologies. H2 evolution by molecular complexes classically involves the formation of metal hydride intermediates. Recently, the use of redox‐active ligands has emerged as an alternate strategy for electron and proton storage. Herein, we examine the electrocatalytic behavior of [CoII(Mabiq)(THF)](PF6) (CoMbq), containing a redox‐active macrocyclic ligand, in acidic, organic media (using para‐cyanoanilinium (pCA) as the proton source). Cyclic voltammetry (CV) and Rotating Ring Disk Electrode (RRDE) voltammetry evidence a pre‐catalytic process that leads to the formation of a protonated, two‐electron reduced intermediate. This species evolves H2 at potentials negative of −1.1 VFc, as confirmed by On‐line Electrochemical Mass Spectrometry (OEMS). OEMS results further reveal a catalyst deactivation pathway. The electrochemical data denote the involvement of the redox‐active Mabiq ligand in the hydrogen evolution reaction (HER), with implications for the use of such scaffolds in electrocatalytic complexes.

show abstract

Section: Introductionmentioning

confidence: 99%

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

et al. 2019

View full text Add to dashboard Cite

show abstract

“…18–20 To this end, there has been a resurgence into redox-active, 20,21 hemilabile, 23–27 and so called proton-responsive ligand scaffolds 28–40 However, studies that incorporate the triad of redox-activity, hemilability, and proton responsivity, all in a single ligand scaffold, are exceedingly limited. 41–47 Our group has been active in developing methodologies that control the movement of both protons and electrons for biologically relevant reactions by utilizing the redox-active pyridinediimine (PDI) scaffold merged with a proton-responsive secondary coordination sphere. 48–50 Those preliminary studies successfully showed: 1) the PDI scaffold can be tailored to facilitate NO 2 − reduction, and; 2) the NO 2 − reduction is dependent on the protonation state of the secondary coordination sphere (proton-responsivity).…”

Section: Introductionmentioning

confidence: 99%

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction

et al. 2018

View full text Add to dashboard Cite

Incorporation of the triad of redox-activity, hemilability, and proton responsivity, into a single ligand scaffold is reported. Due to this triad, the complexes Fe(PyrrPDI)(CO)2 (3) and Fe(MorPDI)(CO)2 (4) display 40-fold enhancements in the initial rate of NO2− reduction, with respect to Fe(MeOPDI)(CO)2 (7). Utilizing the proper sterics and pKa of the pendant base(s) to introduce hemilability into our ligand scaffolds, we report unusual {FeNO}x mononitrosyl iron complexes (MNICs) as intermediates in the NO2− reduction reaction. The {FeNO}x species behave spectroscopically and computationally similar to {FeNO}7, an unusual intermediate-spin Fe(III) coupled to triplet NO− and a singly-reduced PDI ligand. These {FeNO}x MNICs facilitate the enhancements in the initial rate.

show abstract

“…53 Synthetic systems where designed ancillary ligands can donate both protons and electrons have been an area of increasing interest. 4,23,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] However, leveraging this strategy for the biomimetic activation of O2 has not been explored. We reasoned that the previously reported pyrrole-based ligand scaffold tBu,Tol DHP ( tBu,Tol DHP = 2,5bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole, Scheme 1), which can donate two electrons and two protons to a substrate, would be an ideal scaffold to demonstrate this principle.…”

Section: Enzymaticmentioning

confidence: 99%

Direct Aerobic Generation of a Ferric Hydroperoxo Intermediate via a Preorganized Secondary Coordination Sphere

Jesse

Anferov

Collins³

et al. 2021

Preprint

View full text Add to dashboard Cite

Enzymes exert control over the reactivity of metal centers with precise tuning of the secondary coordination sphere of active sites. One particularly elegant illustration of this principle is in the controlled delivery of proton and electron equivalents in order to activate abundant but kinetically inert oxidants such as O2 for oxidative chemistry. Chemists have drawn inspiration from biology in designing molecular systems where the secondary coordination sphere can shuttle protons or electrons to substrates. However, a biomimetic activation of O2 requires the transfer of both protons and electrons, and molecular systems where ancillary ligands are designed to provide both of these equivalents are comparatively rare. Here we report the use of a dihydrazonopyrrole (DHP) ligand complexed to Fe to perform exactly such a biomimetic activation of O2. In the presence of O2, this complex directly generates a high spin Fe(III)-hydroperoxo intermediate which features a DHP • ligand radical via ligand-based transfer of an H-atom. This system displays oxidative reactivity and ultimately releases hydrogen peroxide, providing insight on how secondary coordination sphere interactions influence the evolution of oxidizing intermediates in Fe-mediated aerobic oxidations.

show abstract

Hydrogen-Atom Noninnocence of a Tridentate [SNS] Pincer Ligand

Cited by 34 publications

References 60 publications

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction

Direct Aerobic Generation of a Ferric Hydroperoxo Intermediate via a Preorganized Secondary Coordination Sphere

Contact Info

Product

Resources

About

Hydrogen-Atom Noninnocence of a Tridentate [SNS] Pincer Ligand

Cited by 34 publications

References 60 publications

Electrocatalytic H2 Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Electrocatalytic H2 Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}x and Significant Rate Enhancements in NO2– Reduction

Direct Aerobic Generation of a Ferric Hydroperoxo Intermediate via a Preorganized Secondary Coordination Sphere

Contact Info

Product

Resources

About

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Electrocatalytic H₂ Evolution by the Co‐Mabiq Complex Requires Tempering of the Redox‐Active Ligand

Hemilabile Proton Relays and Redox Activity Lead to {FeNO}^x and Significant Rate Enhancements in NO₂^– Reduction