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

Keywords

High oxidation state
Homogeneous catalysis
Manganese
Oxygen evolution
Water splitting

ASJC Scopus subject areas

Inorganic Chemistry

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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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