Harnessing the Oxidative Power of Monooxygenases through Electrochemistry

Liu, Jeffrey J.; Marinescu, Smaranda C.

doi:10.1021/acscentsci.9b00320

“…Ligand-based storage of electrons is an important motif in transition-metal reactivity and catalysis. − An archetypal example is found in nature, where oxidation of the porphyrin ligand in heme systems enables the activation of O 2 for further oxidative reactivity. − Despite the utility of ligand-based redox chemistry, most aerobic oxidations in biological and synthetic systems still require metals such as Fe and Cu with accessible redox couples such as Fe(II)/(III)/(IV) and Cu(I)/(II). − In contrast to these cases, accessing Ni (II/III) or (II/IV) redox couples is less facile, and Ni-mediated aerobic oxidations are comparatively rare. − In biological systems such as Ni superoxide dismutase, the Ni(II)/(III) redox potential must be specifically tuned by the ligand environment, mainly via strongly donating thiolate ligands. , Recently, however, an alternative mechanism involving electron transfer from an ancillary ligand to O 2 to generate a Ni(II) superoxo complex has been invoked in the Ni-containing enzyme quercetin dioxygenase. , Nickel-superoxo species are generally rare even in synthetic systems, and Ni-mediated oxygen activation without accessing Ni(I) or Ni(III) oxidation states has little synthetic precedent. − Therefore, the proposed enzymatic mechanism for quercetin dioxygenase motivates studies to examine whether ligand cooperativity is a viable strategy for Ni systems to activate O 2 and mediate oxidative transformations.…”

Section: Introductionmentioning

confidence: 99%

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

McNeece

¹

,

Jesse

²

,

Xie

³

et al. 2020

View full text Add to dashboard Cite

Metal ligand cooperativity is a powerful strategy in transition metal chemistry. This type of mechanism for the activation of O 2 is best exemplified by heme centers in biological systems. While aerobic oxidations with Fe and Cu are well precedented, Ni-based oxidations are frequently less common due to less-accessible metal-based redox couples. Some Ni enzymes utilize special ligand environments for tuning the Ni(II)/(III) redox couple such as strongly donating thiolates in Ni superoxide dismutase. A recently characterized example of a Ni-containing protein, however, suggests an alternative strategy for mediating redox chemistry with Ni by utilizing ligand-based reducing equivalents to enable oxygen binding. While this mechanism has little synthetic precedent, we show here that Ni complexes of the redox-active ligand tBu,Tol DHP ( tBu,Tol DHP = 2,5-bis((2-tbutylhydrazono)(p-tolyl)methyl)-pyrrole) activate O 2 to generate a Ni(II) superoxo complex via ligand-based electron transfer. This superoxo complex is competent for stoichiometric oxidation chemistry with alcohols and hydrocarbons. This work demonstrates that coupling ligand-based redox chemistry with functionally redox-inactive Ni centers enables oxidative transformations more commonly mediated by metals such as Fe and Cu.

show abstract

“…1 H NMR of tBu,Tol DHP………………………………………………...….S7 Figure S2. 13 C{ 1 H} NMR of tBu,Tol DHP ……………………….….….….…..…...…S7 Figure S3. 1 H NMR of 1……………………………………………......…..…...........S8 Figure S4.…”

Section: Synthesis Of 3 By Reaction Of 2 With Ko2mentioning

confidence: 99%

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

McNeece¹,

Jesse²,

Xie³

et al. 2020

Preprint

0

View full text Add to dashboard Cite

Metal ligand cooperativity is a powerful strategy in transition metal chemistry. This type of mechanism for the activation of O2 is best exemplified by heme centers in biological systems. While aerobic oxidations with Fe and Cu are well precedented, Ni-based oxidations are frequently less common due to less-accessible metal-based redox couples. Some Ni enzymes utilize special ligand environments for tuning the Ni(II)/(III) redox couple such as strongly donating thiolates in Ni superoxide dismutase. A recently characterized example of a Ni-containing protein, however, suggests an alternative strategy for mediating redox chemistry with Ni by utilizing ligand-based reducing equivalents to enable oxygen binding. While this mechanism has little synthetic precedent, we show here that Ni complexes of the redox-active ligand tBu,TolDHP (tBu,TolDHP = 2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) activate O2 to generate a Ni(II) superoxo complex via ligand-based electron transfer. This superoxo complex is competent for stoichiometric oxidation chemistry with alcohols and hydrocarbons. This work demonstrates that coupling ligand-based redox chemistry with functionally redox-inactive Ni centers enables oxidative transformations more commonly mediated by metals such as Fe and Cu.

show abstract

“…[1][2][3][4][5][6][7][8][9][10][11][12] An archetypal example is found in nature, where oxidation of the porphyrin ligand in heme systems enables the activation of O2 for further oxidative reactivity. [13][14][15][16][17][18][19][20] Despite the utility of ligand-based redox chemistry, most aerobic oxidations in biological and synthetic systems still require metals such as Fe and Cu with accessible redox couples such as Fe(II)/(III)/(IV) and Cu(I)/(II). [21][22][23][24][25][26][27][28] In contrast to these cases, accessing Ni (II/III) or (II/IV) redox couples is less facile and corresponding Ni mediated aerobic oxidations are comparatively rare.…”

mentioning

confidence: 99%

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

McNeece¹,

Jesse²,

Xie³

et al. 2020

Preprint

View full text Add to dashboard Cite

Metal ligand cooperativity is a powerful strategy in transition metal chemistry. This type of mechanism for the activation of O2 is best exemplified by heme centers in biological systems. While aerobic oxidations with Fe and Cu are well precedented, Ni-based oxidations are frequently less common due to less-accessible metal-based redox couples. Some Ni enzymes utilize special ligand environments for tuning the Ni(II)/(III) redox couple such as strongly donating thiolates in Ni superoxide dismutase. A recently characterized example of a Ni-containing protein, however, suggests an alternative strategy for mediating redox chemistry with Ni by utilizing ligand-based reducing equivalents to enable oxygen binding. While this mechanism has little synthetic precedent, we show here that Ni complexes of the redox-active ligand tBu,TolDHP (tBu,TolDHP = 2,5-bis((2-t-butylhydrazono)(p-tolyl)methyl)-pyrrole) activate O2 to generate a Ni(II) superoxo complex via ligand-based electron transfer. This superoxo complex is competent for stoichiometric oxidation chemistry with alcohols and hydrocarbons. This work demonstrates that coupling ligand-based redox chemistry with functionally redox-inactive Ni centers enables oxidative transformations more commonly mediated by metals such as Fe and Cu.

show abstract

Harnessing the Oxidative Power of Monooxygenases through Electrochemistry

Abstract: A newly designed bioinspired electrocatalyst unlocks the oxidative power of dioxygen to functionalize unactivated C−H bonds and olefins.

Cited by 4 publications

References 11 publications

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

Generation and Oxidative Reactivity of a Ni(II) Superoxo Complex via Ligand-Based Redox Non-Innocence

Contact Info

Product

Resources

About