Intramolecular C–H and C–F Bond Oxygenation by Site-Differentiated Tetranuclear Manganese Models of the OEC
Abstract
The dangler manganese center in the oxygen-evolving complex (OEC) of photosystem II plays an important role in the oxidation of water to dioxygen. Inspired by the structure of the OEC, we synthesized a series of site-differentiated tetra-manganese clusters [LMn_3(PhPz)_3OMn][OTf]_x (2: x= 2; 3: x = 1) that features an apical manganese ion—distinct from the others—that is appended to a trinuclear manganese core through an μ4-oxygen atom bridge. This cluster design was targeted to facilitate studies of high-valent Mn-oxo formation, which is a proposed step in the mechanism for water oxidation by the OEC. Terminal Mn-oxo species—supported by a multinuclear motif—were targeted by treating 2 and 3 with iodosobenzene. Akin to our previously reported iron complexes, intramolecular arene hydroxylation was observed to yield the C–H bond oxygenated complexes [LMn3(PhPz)_2(OArPz)OMn][OTf]x (5: x = 2; 6: x = 1). The fluorinated series [LMn_3(F_2ArPz)_3OMn][OTf]_x (8: x = 2; 9: x = 1) was also synthesized to mitigate the observed intramolecular hydroxylation. Treatment of 8 and 9 with iodosobenzene results in intramolecular arene C–F bond oxygenation as judged by electrospray ionization mass spectrometry. The observed aromatic C–H and C–F hydroxylation is suggestive of a putative high-valent terminal metal-oxo species, and it is one of the very few examples capable of oxygenating C–F bonds.
Additional Information
© 2017 American Chemical Society. Received: April 27, 2017; Published: July 21, 2017. This research was supported by the NIH (R01-GM102687B). T.A. is grateful for a Dreyfus fellowship. K.M.C. was a Larson Fellow and a recipient of the Caltech Summer Undergraduate Research Fellowship (SURF). We thank M. K. Takase and L. M. Henling for assistance with X-ray crystallography. The authors declare no competing financial interest.Attached Files
Accepted Version - nihms913580.pdf
Supplemental Material - ic7b01022_si_001.pdf
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Additional details
- PMCID
- PMC5669799
- Eprint ID
- 79305
- Resolver ID
- CaltechAUTHORS:20170724-125851935
- R01-GM102687B
- NIH
- Camille and Henry Dreyfus Foundation
- Caltech Summer Undergraduate Research Fellowship (SURF)
- Created
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2017-07-24Created from EPrint's datestamp field
- Updated
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2022-03-23Created from EPrint's last_modified field