Structural Effects on Dioxygen Evolution from Ru(V)−Oxo Complexes

Swann, Matthew T.; Nicholas, Kenneth M.

doi:10.1002/ejic.202100361

Cited by 3 publications

(3 citation statements)

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“…We first optimized the bimetallic peroxo species 8 as the triplet; the resulting structure is shown in Figure 37. The bridged peroxo species 8 has an anti conformation of the Mo‐O−O‐Mo unit (dihedral angle=178°), as has often been seen for other bimetallic η 1 ,η 1 ‐peroxo derivatives and organic peroxides [69–71] . It is symmetrical around the bridging dioxygen moiety, with an O−O bond length (1.42 Å), comparable to the peroxo group of the monometallic oxo‐peroxo Mo(VI) species 5 and marginally shorter than in the Mo(IV) monoperoxo complex 7 .…”

Section: Resultsmentioning

confidence: 75%

“…The bridged peroxo species 8 has an anti conformation of the Mo-OÀ O-Mo unit (dihedral angle = 178°), as has often been seen for other bimetallic η 1 ,η 1 -peroxo derivatives and organic peroxides. [69][70][71] It is symmetrical around the bridging dioxygen moiety, with an OÀ O bond length (1.42 Å), comparable to the peroxo group of the monometallic oxo-peroxo Mo(VI) species 5 and marginally shorter than in the Mo(IV) monoperoxo complex 7. A singlet peroxo species 1 8 appears to be unstable, since attempts to optimize it lead to OÀ O bond dissociation.…”

Section: Potential Regeneration Of (Cy-salen)moo 2 (1) From (Cysalen)...mentioning

confidence: 99%

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Reaction Pathway for the Aerobic Oxidation of Phosphines Catalyzed by Oxomolybdenum Salen Complexes

Rusmore,

Lander,

Nicholas

2023

Eur J Inorg Chem

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Catalysis of O‐atom transfer (OAT) reactions is a characteristic of both natural (enzymatic) and synthetic molybdenum‐oxo and ‐peroxo complexes. These reactions can employ a variety of terminal oxidants, e. g. DMSO, N‐oxides, and peroxides, etc., but rarely molecular oxygen. Here we demonstrate the ability of a set of Schiff‐base‐MoO2 complexes (cy‐salen)MoO2 (cy‐salen=N,N’‐cyclohexyl‐1,2‐bis‐salicylimine) to catalyze the aerobic oxidation of PPh3. We also report the results of a DFT computational investigation of the catalytic pathway, including the identification of energetically accessible intermediates and transition states, for the aerobic oxidation of PMe3. Starting from the dioxo species, (cy‐salen)Mo(VI)O2 (1), key reaction steps include: 1) associative addition of PMe3 to an oxo‐O to give LMo(IV)(O)(OPMe3) (2); 2) OPMe3 dissociation from 2 to produce mono‐oxo complex (cy‐salen)Mo(IV)O (3); 3) stepwise O2 association with 3 via superoxo species (cy‐salen)Mo(V)(O)(η1‐O2) (4) to form the oxo‐peroxo intermediate (cy‐salen)Mo(VI)(O)(η2‐O2) (5); 4) the O‐transfer reaction of PMe3 with oxo‐peroxo species 5 at the oxo‐group, rather than the peroxo unit leading, after OPMe3 dissociation, to a monoperoxo species, (cy‐salen)Mo(IV)(η2‐O2) (7); and 5) regeneration of the dioxo complex (cy‐salen)Mo(VI)O2 (1) from the monoperoxo triplet 37 or singlet 17 by a concerted, asynchronous electronic isomerization. An alternative pathway for recycling of the oxo‐peroxo species 5 to the dioxo‐Mo 1 via a bimetallic peroxo complex LMo(O)‐O−O‐Mo(O)L 8 is determined to be energetically viable, but is unlikely to be competitive with the primary pathway for aerobic phosphine oxidation catalyzed by 1.

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Section: Resultsmentioning

confidence: 75%

Section: Potential Regeneration Of (Cy-salen)moo 2 (1) From (Cysalen)...mentioning

confidence: 99%

Reaction Pathway for the Aerobic Oxidation of Phosphines Catalyzed by Oxomolybdenum Salen Complexes

Rusmore,

Lander,

Nicholas

2023

Eur J Inorg Chem

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“…During the oxygen evolution (OE) phase of the N 2 O splitting process, Cl(POR)Ru(V)O ( B-3 ) is converted via dimerization to a Ru 2 peroxo species, followed by Cl(POR)Ru dissociation to a Ru-dioxygen complex and finally dissociation of the latter to O 2 and Cl(POR)Ru. Since we recently evaluated this sequence computationally in a study of water splitting by various LRu(III) complexes, we will only briefly highlight the key features and energetics here. The intermediates and transition states located for this sequence are summarized in Scheme , along with the free energy changes calculated for each step.…”

Section: Resultsmentioning

confidence: 99%

Computational Evaluation of Potential Molecular Catalysts for Nitrous Oxide Decomposition

2022

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Nitrous oxide (N 2 O) is a potent greenhouse gas (GHG) with limited use as a mild anesthetic and underdeveloped reactivity. Nitrous oxide splitting (decomposition) is critical to its mitigation as a GHG. Although heterogeneous catalysts for N 2 O decomposition have been developed, highly efficient, long-lived solid catalysts are still needed, and the details of the catalytic pathways are not well understood. Reported herein is a computational evaluation of three potential molecular (homogeneous) catalysts for N 2 O splitting, which could aid in the development of more active and robust catalysts and provide deeper mechanistic insights: one Cu(I)-based, [(CF 3 O) 4 Al]Cu (A-1), and two Ru(III)-based, Cl(POR)Ru (B-1) and (NTA)Ru (C-1) (POR = porphyrin, NTA = nitrilotriacetate). The structures and energetic viability of potential intermediates and key transition states are evaluated according to a two-stage reaction pathway: (A) deoxygenation (DO), during which a metal−N 2 O complex undergoes N−O bond cleavage to produce N 2 and a metal−oxo species and (B) (di)oxygen evolution (OER), in which the metal−oxo species dimerizes to a dimetal− peroxo complex, followed by conversion to a metal−dioxygen species from which dioxygen dissociates. For the (F−L)Cu(I) activator (A-1), deoxygenation of N 2 O is facilitated by an O-bound (F−L)Cu−O−N 2 or better by a bimetallic N,O-bonded, (F− L)Cu−NNO−Cu(F−L) complex; the resulting copper−oxyl (F−L)Cu−O is converted exergonically to (F−L)Cu−(η 2 ,η 2 -O 2 )− Cu(F−L), which leads to dioxygen species (F−L)Cu(η 2 -O 2 ), that favorably dissociates O 2 . Key features of the DO/OER process for (POR)ClRu (B-1) include endergonic N 2 O coordination, facile N 2 evolution from LR′u−N 2 O−RuL to Cl(POR)RuO, moderate barrier coupling of Cl(POR)RuO to peroxo Cl(POR)Ru(O 2 )Ru(POR)Cl, and eventual O 2 dissociation from Cl(POR)Ru(η 1 -O 2 ), which is nearly thermoneutral. N 2 O decomposition promoted by (NTA)Ru(III) (C-1) can proceed with exergonic N 2 O coordination, facile N 2 dissociation from (NTA)Ru−ON 2 or (NTA)Ru−N 2 O−Ru(NTA) to form (NTA)Ru−O; dimerization of the (NTA)Ru-oxo species is facile to produce (NTA)Ru−O−O−Ru(NTA), and subsequent OE from the peroxo species is moderately endergonic. Considering the overall energetics, (F−L)Cu and Cl(POR)Ru derivatives are deemed the best candidates for promoting facile N 2 O decomposition.

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Tailoring atomic chemistry to refine reaction pathway for the most enhancement by magnetization in water oxidation

Wu,

Ge,

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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Water oxidation on magnetic catalysts has generated significant interest due to the spin-polarization effect. Recent studies have revealed that the disappearance of magnetic domain wall upon magnetization is responsible for the observed oxygen evolution reaction (OER) enhancement. However, an atomic picture of the reaction pathway remains unclear, i.e., which reaction pathway benefits most from spin-polarization, the adsorbent evolution mechanism, the intermolecular mechanism (I2M), the lattice oxygen-mediated one, or more? Here, using three model catalysts with distinguished atomic chemistries of active sites, we are able to reveal the atomic-level mechanism. We found that spin-polarized OER mainly occurs at interconnected active sites, which favors direct coupling of neighboring ligand oxygens (I2M). Furthermore, our study reveals the crucial role of lattice oxygen participation in spin-polarized OER, significantly facilitating the coupling kinetics of neighboring oxygen radicals at active sites.

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Structural Effects on Dioxygen Evolution from Ru(V)−Oxo Complexes

Cited by 3 publications

References 96 publications

Reaction Pathway for the Aerobic Oxidation of Phosphines Catalyzed by Oxomolybdenum Salen Complexes

Reaction Pathway for the Aerobic Oxidation of Phosphines Catalyzed by Oxomolybdenum Salen Complexes

Computational Evaluation of Potential Molecular Catalysts for Nitrous Oxide Decomposition

Tailoring atomic chemistry to refine reaction pathway for the most enhancement by magnetization in water oxidation

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