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N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox‐Leveling, High Mn Oxidation States, and a Mn 2 O 2 Dimer Competent for Catalytic Oxygen Evolution
Author(s) -
Lant Hannah M. C.,
Michaelos Thoe K.,
Sharninghausen Liam S.,
Mercado Brandon Q.,
Crabtree Robert H.,
Brudvig Gary W.
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201801343
Subject(s) - chemistry , dimer , moiety , dication , redox , protonation , catalysis , alkoxide , ligand (biochemistry) , electron paramagnetic resonance , medicinal chemistry , oxygen , inorganic chemistry , alcohol oxidation , oxygen evolution , photochemistry , pincer movement , electrochemistry , stereochemistry , molecule , organic chemistry , ion , biochemistry , physics , receptor , electrode , nuclear magnetic resonance
The new complex [Mn(bipyalk)(H 2 O)(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 KHSO 5 in water. It is proposed on the basis of EPR experiments that the catalyst proceeds through a Mn V (µ‐O) 2 Mn 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)Cl 2 . A related series of bis‐ligated monomers of the type [Mn n (bipyalkH x )(bipyalkH y )](PF 6 ) 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.