N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox-Leveling, High Mn Oxidation States, and a Mn2O2 Dimer Competent for Catalytic Oxygen Evolution

Hannah M.C. Lant; Thoe K. Michaelos; Liam S. Sharninghausen; Brandon Q. Mercado; Robert H. Crabtree; Gary W Brudvig

doi:10.1002/ejic.201801343

N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox-Leveling, High Mn Oxidation States, and a Mn₂O₂ Dimer Competent for Catalytic Oxygen Evolution

Hannah M.C. Lant, Thoe K. Michaelos, Liam S. Sharninghausen, Brandon Q. Mercado, Robert H. Crabtree, Gary W Brudvig

Yale University

Research output: Contribution to journal › Article

2 Citations (Scopus)

Abstract

The new complex [Mn(bipyalk)(H₂O)(µ-O)]₂(OTf)₂ {bipyalk = 2-([2,2′-bipyridin]-6-yl)propan-2-olate} catalyzes oxygen evolution with a TOF of 0.0055 s^–1 when driven by the sacrificial oxidant KHSO₅ in water. It is proposed on the basis of EPR experiments that the catalyst proceeds through a Mn^V(µ-O)₂Mn^V=O intermediate supported by the highly donating tertiary alkoxide moiety of the ligand. The Mn(IV,IV) dimer can also be formed electrochemically from its precursor, Mn(bipyalkH)Cl₂. A related series of bis-ligated monomers of the type [Mnⁿ(bipyalkH_x)(bipyalkH_y)](PF₆)₂ is also reported, where the dication features Mn^II, Mn^III, and Mn^IV oxidation states and corresponding protonation states. Electrochemical data on this series underscore the importance of proton loss at the alcohol/alkoxide moiety during oxidation to maintain low overpotentials required for catalysis.

Original language	English
Journal	European Journal of Inorganic Chemistry
DOIs	https://doi.org/10.1002/ejic.201801343
Publication status	Published - Jan 1 2019

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Keywords

High oxidation state
Homogeneous catalysis
Manganese
Oxygen evolution
Water splitting

ASJC Scopus subject areas

Inorganic Chemistry

Cite this

Lant, H. M. C., Michaelos, T. K., Sharninghausen, L. S., Mercado, B. Q., Crabtree, R. H., & Brudvig, G. W. (2019). N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox-Leveling, High Mn Oxidation States, and a Mn₂O₂ Dimer Competent for Catalytic Oxygen Evolution. European Journal of Inorganic Chemistry. https://doi.org/10.1002/ejic.201801343

N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox-Leveling, High Mn Oxidation States, and a Mn₂O₂ Dimer Competent for Catalytic Oxygen Evolution. / Lant, Hannah M.C.; Michaelos, Thoe K.; Sharninghausen, Liam S.; Mercado, Brandon Q.; Crabtree, Robert H.; Brudvig, Gary W.

In: European Journal of Inorganic Chemistry, 01.01.2019.

Research output: Contribution to journal › Article

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title = "N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox-Leveling, High Mn Oxidation States, and a Mn2O2 Dimer Competent for Catalytic Oxygen Evolution",

abstract = "The new complex [Mn(bipyalk)(H2O)(µ-O)]2(OTf)2 {bipyalk = 2-([2,2′-bipyridin]-6-yl)propan-2-olate} catalyzes oxygen evolution with a TOF of 0.0055 s–1 when driven by the sacrificial oxidant KHSO5 in water. It is proposed on the basis of EPR experiments that the catalyst proceeds through a MnV(µ-O)2MnV=O intermediate supported by the highly donating tertiary alkoxide moiety of the ligand. The Mn(IV,IV) dimer can also be formed electrochemically from its precursor, Mn(bipyalkH)Cl2. A related series of bis-ligated monomers of the type [Mnn(bipyalkHx)(bipyalkHy)](PF6)2 is also reported, where the dication features MnII, MnIII, and MnIV oxidation states and corresponding protonation states. Electrochemical data on this series underscore the importance of proton loss at the alcohol/alkoxide moiety during oxidation to maintain low overpotentials required for catalysis.",

keywords = "High oxidation state, Homogeneous catalysis, Manganese, Oxygen evolution, Water splitting",

author = "Lant, {Hannah M.C.} and Michaelos, {Thoe K.} and Sharninghausen, {Liam S.} and Mercado, {Brandon Q.} and Crabtree, {Robert H.} and Brudvig, {Gary W}",

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AU - Lant, Hannah M.C.

AU - Michaelos, Thoe K.

AU - Sharninghausen, Liam S.

AU - Mercado, Brandon Q.

AU - Crabtree, Robert H.

AU - Brudvig, Gary W

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N2 - The new complex [Mn(bipyalk)(H2O)(µ-O)]2(OTf)2 {bipyalk = 2-([2,2′-bipyridin]-6-yl)propan-2-olate} catalyzes oxygen evolution with a TOF of 0.0055 s–1 when driven by the sacrificial oxidant KHSO5 in water. It is proposed on the basis of EPR experiments that the catalyst proceeds through a MnV(µ-O)2MnV=O intermediate supported by the highly donating tertiary alkoxide moiety of the ligand. The Mn(IV,IV) dimer can also be formed electrochemically from its precursor, Mn(bipyalkH)Cl2. A related series of bis-ligated monomers of the type [Mnn(bipyalkHx)(bipyalkHy)](PF6)2 is also reported, where the dication features MnII, MnIII, and MnIV oxidation states and corresponding protonation states. Electrochemical data on this series underscore the importance of proton loss at the alcohol/alkoxide moiety during oxidation to maintain low overpotentials required for catalysis.

AB - The new complex [Mn(bipyalk)(H2O)(µ-O)]2(OTf)2 {bipyalk = 2-([2,2′-bipyridin]-6-yl)propan-2-olate} catalyzes oxygen evolution with a TOF of 0.0055 s–1 when driven by the sacrificial oxidant KHSO5 in water. It is proposed on the basis of EPR experiments that the catalyst proceeds through a MnV(µ-O)2MnV=O intermediate supported by the highly donating tertiary alkoxide moiety of the ligand. The Mn(IV,IV) dimer can also be formed electrochemically from its precursor, Mn(bipyalkH)Cl2. A related series of bis-ligated monomers of the type [Mnn(bipyalkHx)(bipyalkHy)](PF6)2 is also reported, where the dication features MnII, MnIII, and MnIV oxidation states and corresponding protonation states. Electrochemical data on this series underscore the importance of proton loss at the alcohol/alkoxide moiety during oxidation to maintain low overpotentials required for catalysis.

KW - High oxidation state

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KW - Water splitting

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10.1002/ejic.201801343