Reactivity of hydride bridges in a high-spin [Fe3(μ-H)3]3+ cluster: reversible H2/CO exchange and Fe–H/B–F bond metathesis

Anderton, Kevin J.; Knight, Brian J.; Rheingold, Arnold L.; Abboud, Khalil A.; García-Serres, Ricardo; Murray, Leslie J.

doi:10.1039/c6sc05583d

Cited by 23 publications

(29 citation statements)

References 84 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previously, hydridicity of metal hydrides has been correlated to solvent acceptor number, consistent with the observed solvent effect for reaction of 1 with CO 2 , , , . Taken together with the reactivity of Fe 3 H 3 L Et/Me with CO which results in H 2 reductive elimination, we proposed that the hydrides in these clusters are coordinatively fluxional and capable of adopting semi‐bridging or terminal modes. Herein, we report a detailed kinetic study of the reaction of 1 with CO 2 to generate 1‐CO 2 using in situ 1 H‐NMR and UV/Visible spectroscopy.…”

Section: Introductionsupporting

confidence: 84%

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Hong

Murray

2019

Eur J Inorg Chem

Self Cite

View full text Add to dashboard Cite

The reduction of CO2 to formic acid by transition metal hydrides is a potential pathway to access reactive C1 compounds. To date, no kinetic study has been reported for insertion of a bridging hydride in a weak‐field ligated complex into CO2; such centers have relevance to metalloenzymes that catalyze this reaction. Herein, we report the kinetic study of the reaction of a tri(µ‐hydride)triiron(II/II/II) cluster supported by a tris(β‐diketimine) cyclophane (1) with CO2 monitored by 1H‐NMR and temperature‐controlled UV/Vis spectroscopy. We found that 1 reacts with CO2 to traverse the reported monoformate (1‐CO2) and a diformate complex (1‐2CO2) at 298 K in toluene, and ultimately yields the triformate species (1‐3CO2) at elevated temperature. The second order rate constant, H/D kinetic isotope effect, ΔH‡, and ΔS‡ for formation of 1‐CO2 were determined as 8.4(3) × 10–4 m–1 s–1, 1.08(9), 11(1) kcal mol–1, and –3(1) × 10 cal mol–1 K–1, respectively at 298 K. These parameters suggest that CO2 coordination to the iron centers does not coordinate prior to the rate controlling step whereas Fe–H bond cleavage does.

show abstract

Section: Introductionsupporting

confidence: 84%

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Hong

Murray

2019

Eur J Inorg Chem

Self Cite

View full text Add to dashboard Cite

show abstract

“…52 In contrast to the well-defined reactivity of 3 , reactions of CO with synthetic, high spin iron(II/III) clusters typically result in cluster fragmentation and the formation of reduced, low spin iron carbonyl clusters, 23–24 further illustrating the advantages of employing robust ligand scaffolds to interrogate chemistry relevant to nitrogenase. 29,36…”

Section: Resultsmentioning

confidence: 99%

A Thermodynamic Model for Redox-Dependent Binding of Carbon Monoxide at Site-Differentiated, High Spin Iron Clusters

2018

View full text Add to dashboard Cite

Binding of N and CO by the FeMo-cofactor of nitrogenase depends on the redox level of the cluster, but the extent to which pure redox chemistry perturbs the affinity of high spin iron clusters for π-acids is not well understood. Here, we report a series of site-differentiated iron clusters that reversibly bind CO in redox states Fe through FeFe. One electron redox events result in small changes in the affinity for (at most ∼400-fold) and activation of CO (at most 28 cm for ν). The small influence of redox chemistry on the affinity of these high spin, valence-localized clusters for CO is in stark contrast to the large enhancements (10-10 fold) in π-acid affinity reported for monometallic and low spin, bimetallic iron complexes, where redox chemistry occurs exclusively at the ligand binding site. While electron-loading at metal centers remote from the substrate binding site has minimal influence on the CO binding energetics (∼1 kcal·mol), it provides a conduit for CO binding at an Fe center. Indeed, internal electron transfer from these remote sites accommodates binding of CO at an Fe, with a small energetic penalty arising from redox reorganization (∼2.6 kcal·mol). The ease with which these clusters redistribute electrons in response to ligand binding highlights a potential pathway for coordination of N and CO by FeMoco, which may occur on an oxidized edge of the cofactor.

show abstract

“…The experimental and computational analysis presented above demonstrates that Fe-S clusters can achieve low-valent electronic configurations at individual Fe sites, allowing for substantial activation of π-accepting substrates such as CO. Such configurations are generated by an intracluster electron transfer process that is conceptually related to valence rearrangements observed in other metalloclusters 24,[60][61][62][63] in which the existing metal ion valences are shuffled between cluster sites. However, the processes observed for 1-CO and [1-CO] + are distinct in that CO binding induces generation of valences that were not initially present in the cluster.…”

Section: Resultsmentioning

confidence: 99%

Evidence for Low-valent Electronic Configurations in Iron–Sulfur Clusters

Brown

Thompson

Suess

2022

Preprint

View full text Add to dashboard Cite

Although biological iron-sulfur (Fe–S) clusters perform some of the most difficult redox reactions in Nature, they are thought to be composed exclusively of Fe2+ and Fe3+ ions, as well as mixed-valent pairs with average oxidation states of Fe2.5+. We herein show that Fe–S clusters formally composed of these valences can access a wider range of electronic configurations—in particular, those featuring low-valent Fe1+ centers. We demonstrate that CO binding to a synthetic [Fe4S4]0 cluster supported by N-heterocyclic carbene ligands induces generation of Fe1+ centers via intracluster electron transfer, wherein a neighboring pair of Fe2+ sites reduces the CO-bound site to a low-valent Fe1+ state. Similarly, CO binding to an [Fe4S4]+ cluster induces electron delocalization with a neighboring Fe site to form a mixed-valent Fe1.5+Fe2.5+ pair in which the CO-bound site adopts partial low-valent character. These low-valent configurations engender remarkable C–O bond activation without having to traverse highly negative and physiologically inaccessible Fe2+/Fe1+ redox couples.

show abstract

Reactivity of hydride bridges in a high-spin [Fe₃(μ-H)₃]³⁺ cluster: reversible H₂/CO exchange and Fe–H/B–F bond metathesis

Abstract: The triiron trihydride complex Fe3H3 L (1) [where L 3– is a tris(β-diketiminate)cyclophanate] reacts with CO and with BF3·OEt2 to afford (FeICO)2FeII(μ3-H)L (2) and Fe3F3 L (3), respectively.

Cited by 23 publications

References 84 publications

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

Carbon Dioxide Insertion into Bridging Iron Hydrides: Kinetic and Mechanistic Studies

A Thermodynamic Model for Redox-Dependent Binding of Carbon Monoxide at Site-Differentiated, High Spin Iron Clusters

Evidence for Low-valent Electronic Configurations in Iron–Sulfur Clusters

Contact Info

Product

Resources

About