Partial substitution of ZnII by MnII in Zn4O(terephthalate)3 (MOF-5) leads to a distorted all-oxygen ligand field supporting a single MnII site, whose structure was confirmed by Mn K-edge X-ray absorption spectroscopy. The MnII ion at the MOF-5 node engages in redox chemistry with a variety of oxidants. With tBuSO2PhIO, it produces a putative MnIV-oxo intermediate, which upon further reaction with adventitious hydrogen is trapped as a MnIII–OH species. Most intriguingly, the intermediacy of the high-spin MnIV–oxo species is likely responsible for catalytic activity of the MnII-MOF-5 precatalyst, which in the presence of tBuSO2PhIO catalyzes oxygen atom transfer reactivity to form epoxides from cyclic alkenes with >99% selectivity. These results demonstrate that MOF secondary building units serve as competent platforms for accessing terminal high-valent metal–oxo species that consequently engage in catalytic oxygen atom transfer chemistry owing to the relatively weak ligand fields provided by the SBU.

Selective Catalytic Olefin Epoxidation with MnII-Exchanged MOF-5

Braglia, Luca;Borfecchia, Elisa;Lamberti, Carlo;
2018-01-01

Abstract

Partial substitution of ZnII by MnII in Zn4O(terephthalate)3 (MOF-5) leads to a distorted all-oxygen ligand field supporting a single MnII site, whose structure was confirmed by Mn K-edge X-ray absorption spectroscopy. The MnII ion at the MOF-5 node engages in redox chemistry with a variety of oxidants. With tBuSO2PhIO, it produces a putative MnIV-oxo intermediate, which upon further reaction with adventitious hydrogen is trapped as a MnIII–OH species. Most intriguingly, the intermediacy of the high-spin MnIV–oxo species is likely responsible for catalytic activity of the MnII-MOF-5 precatalyst, which in the presence of tBuSO2PhIO catalyzes oxygen atom transfer reactivity to form epoxides from cyclic alkenes with >99% selectivity. These results demonstrate that MOF secondary building units serve as competent platforms for accessing terminal high-valent metal–oxo species that consequently engage in catalytic oxygen atom transfer chemistry owing to the relatively weak ligand fields provided by the SBU.
2018
8
1
596
601
https://pubs.acs.org/doi/10.1021/acscatal.7b02946
alkene epoxidation; metal-organic framework; manganese(IV)-oxo; manganese(III)-hydroxo; tert-butylsulfonyl-2-iodosylbenzene; oxidation; heterogeneous catalysis; EXAFS; XANES, EPR
Stubbs, Amanda W.; Braglia, Luca; Borfecchia, Elisa; Meyer, Randall J.; Román- Leshkov, Yuriy; Lamberti, Carlo; Dincă, Mircea
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1665422
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