Electrophile-promoted Fe-to-N2hydride migration in highly reduced Fe(N2)(H) complexes

Deegan, Meaghan M.; Peters, Jonas C.

doi:10.1039/c8sc02380h

Cited by 23 publications

(31 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The isolation of 9 , in which the phenyl has not migrated, suggests that the initial silylation of the β position of the coordinated N 2 in 7 takes place before the migration of the aryl group. It is likely that the second silylation induces the aryl migration, because Peters recently reported the migration of H from an iron center to the α position of a doubly silylated N 2 group to form an iron disilylhydrazido complex 27 . Accordingly, addition of excess trimethylsilyl triflate (Me 3 SiOTf) and excess Na to 9 gave a 14% yield of PhN(SiMe 3 ) 2 , showing that addition of a second silyl group can initiate C–N bond formation.…”

mentioning

confidence: 99%

Coupling dinitrogen and hydrocarbons through aryl migration

McWilliams

Broere

Halliday

et al. 2020

Nature

100

112

View full text Add to dashboard Cite

A persistent challenge in chemistry is to activate abundant, yet inert molecules such as hydrocarbons and atmospheric N 2 . In particular, forming C–N bonds from N 2 typically requires a reactive organic precursor 1 , which limits the ability to design catalytic cycles. Here, we report an diketiminate-supported iron system that is able to sequentially activate benzene and N 2 to form aniline derivatives. The key to this new coupling reaction is the partial silylation of a reduced iron-N 2 complex, which is followed by migratory insertion of a benzene-derived phenyl group to the nitrogen. Further reduction releases the nitrogen products, and the resulting iron species can re-enter the cyclic pathway. Using a mixture of sodium powder, crown ether, and trimethylsilyl bromide, an easily prepared diketiminate iron bromide complex 2 can mediate the one-pot conversion of several petroleum-derived compounds into the corresponding silylated aniline derivatives using N 2 as the nitrogen source. Numerous compounds along the cyclic pathway have been isolated and crystallographically characterized; their reactivity outlines the mechanism including the hydrocarbon activation step and the N 2 functionalization step. This strategy incorporates nitrogen atoms from N 2 directly into abundant hydrocarbons.

show abstract

mentioning

confidence: 99%

Coupling dinitrogen and hydrocarbons through aryl migration

McWilliams

Broere

Halliday

et al. 2020

Nature

100

112

View full text Add to dashboard Cite

show abstract

“…Some early TM hydrides such as multinuclear Ti hydride complex can further execute reductive protonation of N forming imido units [30][31] . Except that the highly reduced silyl functionalized Fe(N2)(H)n complex undergoes unusual intramolecular hydride migration to N 32 , no N-H bond formation was observed, however, over the reaction of N2 and late TM hydride complexes owning to the insufficient activation of N2 by electron-deficient TM center 5 . As a matter of fact, the Ru hydride complex [PPh3]3Ru(H2)H2 reacts with N2 forming the dinitrogen complex [PPh3]3Ru(N2)H2 and H2 33 .…”

Section: Resultsmentioning

confidence: 94%

Ternary Ruthenium Complex Hydrides for Ammonia Synthesis

Pan¹,

Guo²,

Hansen³

et al. 2020

Preprint

View full text Add to dashboard Cite

Ammonia is the feedstock for nitrogen fertilizers and a potential carbon-free energy carrier, but the current production emits more CO2 than any other chemical producing reaction in the world. The demand for decarbonizing the ammonia industry by using renewable energy has renewed research interests into catalyst development for effective N2 reduction under mild conditions, a grand scientific challenge. Conventional heterogeneous catalysts based on metallic Fe or Ru mediate dinitrogen dissociation and hydrogenation through a relatively energy-costing pathway. The ternary ruthenium complex hydrides Li4RuH6 and Ba2RuH6 reported in this work, on the other hand, represent an entirely new class of compound catalysts, which are composed of the electron- and H-rich [RuH6] anionic centers for non-dissociative dinitrogen reduction, where hydridic H transports electron and proton between the centers, and the Li(Ba) cations for stabilizing NxHy (x: 0 to 2, y: 0 to 3) intermediates. The dynamic and synergistic involvement of all the components of the ternary complex hydrides facilitates a novel reaction mechanism with a narrow energy span and perfectly balanced kinetic barriers for the multi-step process, leading to ammonia production from N2+H2 with superior kinetics under mild conditions.

show abstract

“…To date, several publications have dealt with the mechanism of ammonia formation on biomimetic catalysts; ,− however, the process of (i) H 2 side product formation (thus, low selectivity) and (ii) catalyst deactivation (thus, low lifetime) are far from being understood. ,,,,− …”

Section: Introductionmentioning

confidence: 99%

“…Although HER and deactivation are seemingly separate aspects of undesired catalyst reactivity, there is growing evidence that these processes are interdependent − (see SI, section 2 for the detailed summary of relevant experimental results). In this paper, to explore the connections, we examine the mechanism of Fe–H bond formation from N 2 RR intermediates and evaluate the HER potential of iron hydrides involved in the catalyst deactivation pathway.…”

Section: Introductionmentioning

confidence: 99%

Demonstrating the Direct Relationship between Hydrogen Evolution Reaction and Catalyst Deactivation in Synthetic Fe Nitrogenases

et al. 2020

View full text Add to dashboard Cite

Synthetic Fe nitrogenases are promising catalysts for atmospheric pressure ammonia synthesis. However, their catalytic efficiency is severely limited by the accompanying hydrogen evolution reaction (HER) and fast catalyst deactivation. In order to reveal the origin of these undesired transformations, we study potential reaction routes of HER, catalyst deactivation, and nitrogen reduction reaction (N2RR) by density functional theory in combination with microkinetic modeling, using a triphosphino-silyl ligated iron complex as model system. Our results show that the most favorable HER cycle is initiated by H2 molecules originated from the noncatalytic reaction of acid and reductant reagents, which can coordinate to a vacant binding site of an Fe complex. Thus, H2 coordination competes with the N2 coordination step of the desired N2RR catalytic cycle, and the resulting Fe–H2 complex can be protonated at both hydrogen atoms to release two H2 molecules. The proposed mechanism, called autocatalytic hydrogen evolution reaction (aHER), explains all experimentally observed results including catalyst deactivation, as aHER intermediates can be easily converted into thermodynamically stable, catalytically inactive monohydrides. Our results suggest that improved efficacy of synthetic Fe nitrogenases can be achieved by several ways: (i) proper ligand modifications hindering the formation of Fe–H2 complexes, (ii) suppressing the noncatalytic H2 formation in the catalytic mixture by different reagent choice, and (iii) using flow or semiflow reactor setup instead of batch reactors and keep the proton and electron reagent excess low.

show abstract

Electrophile-promoted Fe-to-N₂hydride migration in highly reduced Fe(N₂)(H) complexes

Abstract: An emerging challenge in nitrogen fixation catalysis is the formation of hydride species, which can play a role in catalyst deactivation and unproductive hydrogen evolution. A new pathway for productive N–H bond formation from an iron hydride precursor is described.

Cited by 23 publications

References 51 publications

Coupling dinitrogen and hydrocarbons through aryl migration

Coupling dinitrogen and hydrocarbons through aryl migration

Ternary Ruthenium Complex Hydrides for Ammonia Synthesis

Demonstrating the Direct Relationship between Hydrogen Evolution Reaction and Catalyst Deactivation in Synthetic Fe Nitrogenases

Contact Info

Product

Resources

About