N<sub>2</sub>‐to‐NH<sub>3</sub> Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

Buscagan, Trixia M.; Oyala, Paul H.; Peters, Jonas C.

doi:10.1002/ange.201703244

Cited by 48 publications

(29 citation statements)

References 60 publications

(83 reference statements)

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“…32,44 The consumption of proton and electron equivalents for the activation process results in formal H 2 evolution, leading to an overall reduction of 43,44,50 N 2 to NH 3 catalytic efficiency. In some Fe catalyst systems, 51 light can be used to induce H 2 elimination from off-path Fe(H) 2 species, [52][53][54] resulting in the generation of Fe-N 2 motifs, without consumption of proton and electron equivalents, thus enhancing the yields of NH 3 .…”

Section: N 2 -To-nh 3 Catalysis With Transition Metal Complexesmentioning

confidence: 99%

Rethinking the Nitrogenase Mechanism: Activating the Active Site

Buscagan

Rees

2019

Joule

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Metalloenzymes called nitrogenases (N 2 ases) harness the reactivity of transition metals to reduce N 2 to NH 3. Specifically, N 2 ases feature a multimetallic active site, called a cofactor, which binds and reduces N 2. The seven Fe centers and one additional metal center (Mo, V, or Fe) that make up the cofactor are all potential substrate-binding sites. Unraveling the mechanism by which the cofactor binds N 2 and reduces N 2 to NH 3 represents a multifaceted challenge because cofactor activation is required for N 2 binding and functionalization to NH 3. Despite decades of fascinating contributions, the nature of N 2 binding to the active site and the structure of the activated cofactor remain unknown. Herein, we discuss the challenges associated with N 2 reduction and how transition-metal complexes facilitate N 2 functionalization by coordinating N 2. We also review the activation and/or reaction mechanisms reported for small molecule catalysts and the Haber-Bosch catalyst and discuss their potential relevance to biological N 2 fixation. Finally, we survey what is known about the mechanism of N 2 ase and highlight recent X-ray crystallographic studies supporting Fe-S bond cleavage at the active site to generate reactive Fe centers as a potential, underexplored route for cofactor activation. We propose that structural rearrangements, beyond electron and proton transfers, are key in generating the catalytically active state(s) of the cofactor. Understanding these processes will be key to unveiling the mechanism of N 2 binding and reduction.

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Section: N 2 -To-nh 3 Catalysis With Transition Metal Complexesmentioning

confidence: 99%

Rethinking the Nitrogenase Mechanism: Activating the Active Site

Buscagan

Rees

2019

Joule

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“…Various model catalyst complexes for N 2 reduction were synthesized, which contain low‐oxidation‐state central metal (such as Mo, Fe, Co, etc. ) and the supporting ligand that is invariably highly electron donating, such as amides, phosphines, sulfido, and/or cyclic alkyl(amino)carbenes . This indicates that the large charge buffer capacity of the central metal is crucial to the catalytic N 2 ‐to‐NH 3 conversion …”

Section: Introductionmentioning

confidence: 99%

N₂Reduction on Fe‐Based Complexes with Different Supporting Main‐Group Elements: Critical Roles of Anchor and Peripheral Ligands

Jiang

et al. 2018

Small Methods

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homogeneous and heterogeneous catalysts for N 2 reduction. [8][9][10][11][12][13][14][15] Artificial catalysts show a great potential because of high activity and tunability, as well as the flexibility to be incorporated into sophisticated electrode assemblies. [16][17][18] Various model catalyst complexes for N 2 reduction were synthesized, which contain low-oxidationstate central metal (such as Mo, Fe, Co, etc.) [19][20][21][22][23] and the supporting ligand that is invariably highly electron donating, such as amides, [10] phosphines, [24][25][26] sulfido, and/or cyclic alkyl(amino)carbenes. [8,27,28] This indicates that the large charge buffer capacity of the central metal is crucial to the catalytic N 2 -to-NH 3 conversion. [14,29,30] To gain further insight into the redoxflexible character of active site in N 2 reduction, studies have been focused on the role of the interaction between central metal and its linked main-group atom in binding, activating, and functionalizing N 2 . [31][32][33] The landmark work on welldefined Fe-based complex with tris(phosphino)alkyl (XP iPr 3 ) (X = C, [28] Si, [34,35] B [20,36] ) ligand featuring axial C/Si/B donor has established a modestly effective catalyst for N 2 -to-NH 3 conversion by addition of protons and electrons at low temperatures. Among the isostructural BP iPr 3 , CP iPr 3 , and SiP iPr 3 series, the system with the most flexible axial linkage, (BP iPr 3 )Fe, gives the greatest catalytic yield under a common set of reaction conditions. [8,20,28,[35][36][37][38][39][40][41][42][43][44] A recent theoretical study elucidated that the reverse-dative Fe→B bonding is of critical importance for the stabilization of different nitrogen intermediates and oxidation states of the Fe center in the catalytic N 2 -to-NH 3 conversion. [45] The dominant contributions to the dative bond originate from the valence d-shell of the active metal center and corresponding ligand-centered bonding orbitals. [46] In addition to main group donors, the Lewis acidic ancillary metals in bimetallic cobaltdinitrogen complexes were also suggested to enhance the reverse-dative bond flexibility and electronic tuning of the active metal, priming a positive effect on reactivity. [47][48][49][50] Considering the importance of reverse-dative bonding between active metal and Lewis-acidic anchor in the catalytic N 2 fixation, a natural question is what happens with the substitution of the apical B atom of Lewis-acidic character with the Lewis-basic N atom in (XP iPr 3 )Fe complex (X denotes the anchor atom). In general, the presence of strong donor groups, such as amides, phosphines, and nitrogen-heterocyclic (NHC) carbenes, Due to the enigmatic existence of the carbon atom in the MoFeS cluster of iron-molybdenum cofactor (FeMoco), the design of biomimetic model catalysts featuring a dative bond between a transition metal and a main group atom is an important topic for efficient reduction of N 2 to NH 3 at ambient conditions. Different anchor atoms (X) for the trigonal bipyramidal (XP iPr 3 )Fe (X =...

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“…7 Using a binuclear Fe-based hydride complex of [P 2 P'Ph FeH] 2 (m-N 2 ), N 2 reduction in the presence of proton and electron sources can be enhanced likely via a photoinduced-re mechanism. 8 Perhaps more intriguing in the homogeneous nitrogen fixation area is the catalytic reduction of N 2 to NH 3 using H 2 to minimize the energy cost, where hydride complexes may serve as a platform for catalyst design and development.…”

Section: Hydrides For Chemical Transformationmentioning

confidence: 99%

The Power of Hydrides

Guo

Chen

2020

Joule

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Her research focuses on hydride materials for catalytic ammonia synthesis.Jianping Guo is a professor at Dalian Institute of Chemical Physics, Chinese Academy of Sciences. His research focuses on exploring metal hydrides, imides, and amides in the activation and transformation of small molecules including N 2 , H 2 , and NH 3 .Ping Chen is a professor and division head of Hydrogen Energy and Advanced Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. The primary research interests of her group include materials development for hydrogen storage and catalysis.

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N₂‐to‐NH₃ Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

Cited by 48 publications

References 60 publications

Rethinking the Nitrogenase Mechanism: Activating the Active Site

Rethinking the Nitrogenase Mechanism: Activating the Active Site

N₂Reduction on Fe‐Based Complexes with Different Supporting Main‐Group Elements: Critical Roles of Anchor and Peripheral Ligands

The Power of Hydrides

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N2‐to‐NH3 Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

Cited by 48 publications

References 60 publications

Rethinking the Nitrogenase Mechanism: Activating the Active Site

Rethinking the Nitrogenase Mechanism: Activating the Active Site

N2Reduction on Fe‐Based Complexes with Different Supporting Main‐Group Elements: Critical Roles of Anchor and Peripheral Ligands

The Power of Hydrides

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Product

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N₂‐to‐NH₃ Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis

N₂Reduction on Fe‐Based Complexes with Different Supporting Main‐Group Elements: Critical Roles of Anchor and Peripheral Ligands