Selective Catalytic Olefin Epoxidation with MnII-Exchanged MOF-5

Article abstract of DOI:10.1021/acscatal.7b02946

Partial substitution of Zn^II by Mn^II in Zn₄O(terephthalate)₃ (MOF-5) leads to a distorted all-oxygen ligand field supporting a single Mn^II site, whose structure was confirmed by Mn K-edge X-ray absorption spectroscopy. The Mn^II ion at the MOF-5 node engages in redox chemistry with a variety of oxidants. With ^tBuSO₂PhIO, it produces a putative Mn^IV-oxo intermediate, which upon further reaction with adventitious hydrogen is trapped as a Mn^III-OH species. Most intriguingly, the intermediacy of the high-spin Mn^IV-oxo species is likely responsible for catalytic activity of the Mn^II-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.

Full text of DOI:10.1021/acscatal.7b02946

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Article
II
Selective Catalytic Olefin Epoxidation with Mn-Exchanged MOF-5
Amanda W Stubbs, Luca Braglia, Elisa Borfecchia, Randall J.
Meyer, Yuriy Roman-Leshkov, Carlo Lamberti, and Mircea Dinca
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.7b02946 • Publication Date (Web): 30 Nov 2017
Downloaded from http://pubs.acs.org on December 1, 2017
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II
Selective Catalytic Olefin Epoxidation with Mn ꢀ
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Exchanged MOFꢀ5
†
§,#
§
‡
Amanda W. Stubbs, Luca Braglia, Elisa Borfecchia, Randall J. Meyer, Yuriy Románꢀ
¢
§,#
†
Leshkov, Carlo Lamberti, Mircea Dincă *
†
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue,
Cambridge, Massachusetts 02139, United States
§
Department of Chemistry, NIS and CrisDi Interdepartmental Centers, INSTM Reference
Center, University of Turin, Via P Giuria 7, Iꢀ10125, Turin, Italy
#
International research center “Smart Materials”, Southern Federal University, 5 Zorge Street,
RostovꢀonꢀDon, 344090, Russia
‡
Corporate Strategic Research, ExxonMobil Research and Engineering, 1545 Route 22,
Annandale, NJ 08801
¢
Department of Chemical Engineering, Massachusetts Institute of Technology, 77
Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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KEYWORDS
alkene epoxidation, metalꢀorganic framework, manganese(IV)ꢀoxo, manganese(III) hydroxo, tꢀ
butylsulfonylꢀ2ꢀiodosylbenzene, oxidation, heterogeneous catalysis
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ABSTRACT
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Partial substitution of Zn by Mn in Zn O(terephthalate) (MOFꢀ5) leads to a distorted allꢀ
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oxygen ligand field supporting a single Mn site, whose structure was confirmed by Mn Kꢀedge
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Xꢀray absorption spectroscopy. The Mn ion at the MOFꢀ5 node engages in redox chemistry
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with a variety of oxidants. With BuSO PhIO, it produces a putative Mn ꢀoxo intermediate,
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which upon further reaction with adventitious hydrogen is trapped as a Mn ꢀOH species. Most
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intriguingly, the intermediacy of the highꢀspin Mn ꢀoxo species is likely responsible for
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catalytic activity of the Mn ꢀMOFꢀ5 preꢀcatalyst, which in the presence BuSO PhIO catalyzes
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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 highꢀvalent metalꢀoxo species that consequently engage in catalytic oxygen
atom transfer chemistry owing to the relatively weak ligand fields provided by the SBU.
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INTRODUCTION
In catalysis, metalꢀorganic frameworks (MOFs) combine the benefits of heterogeneous
catalysts, such as ease of recovery and product separation, with those of homogeneous catalysts,
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most critically steric and electronic tunability. Furthermore, metal ions comprising MOFs’
secondary building units (SBUs) exhibit biomimetic features that are desirable but difficult to
replicate in homogenous systems. These include high spin electronic configurations, determined
by the weak ligand fields of traditional MOF ligands (e.g. carboxylates, azolates), site isolation,
and multiple open coordination sites. When combined with postꢀsynthetic metal exchange, which
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can be utilized to install nonꢀnative metal ions within a large variety of MOFs, the unique
properties of SBUs can be harnessed to explore fundamentally new coordination chemistry and
catalysis. The versatility of SBUꢀbased chemistry and the particular importance of site isolation
conferred by MOFs was highlighted by us and others in the characterization of highly reactive
species, such as the first example of a ferric hyponitrite in Feꢀexchanged Zn O(terephthalate)3
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(
MOFꢀ5), and the development of industrially relevant catalysts, such as the heterogenization of
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an ionꢀpair molecular catalyst for the selective carbonylation of epoxides, and an ethylene
dimerization catalyst that exhibits an unprecedented combination of activity and selectivity for 1ꢀ
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butene.
Encouraged by these results, we sought to explore the potential utility of cation exchange and
SBU chemistry in reactions that typically suffer from poor selectivity due to uncontrolled radical
processes. A vast set of reactions fits this criterion, but few are as relevant industrially as
hydrocarbon oxidations. Although practiced on a massive industrial scale, hydrocarbon
oxidations typically require the intermediacy of highꢀvalent metalꢀoxygen species whose
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reactivity is difficult to control. Selectivity in these processes is further affected by both kinetics
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and thermodynamics: C—H bonds in oxidized (oxygenated) products are often more reactive
than those of alkanes or olefins, which leads to undesired oxidation of the products and eventual
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formation of CO , the thermodynamic sink. This is most famously exemplified with the
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selective oxidation of methane to methanol, a natural process that is not practiced on industrial
scale because there are no known catalysts that can selectively react with the C—H bonds in
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methane but not those in methanol with sufficient activity. Other targets of industrial interest
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abound and include aromatic oxidations, benzylic oxidations, and olefin epoxidations. Indeed,
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oxygenates represent some of the most versatile commodity chemicals,
justifying the
continued interest in the discovery of new selective oxidation catalysts from both a fundamental
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perspective as well as an applied one. Here, we show that Mn ions supported within the
unusually weakꢀfield zincꢀcarboxylate SBUs of MOFꢀ5 (Figure 1) engage in oxidative reactivity
and serve as selective catalysts for the epoxidation of cyclopentene, through the likely
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intermediacy of a highꢀspin Mn ꢀoxo complex.
O
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Mn
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Zn
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Figure 1. MnZn O(terephthalate) cluster
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We selected MnꢀMOFꢀ5 as a potential preꢀcatalyst because it offers a unique coordination
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environment around redoxꢀactive Mn ions. Examples of mononuclear Mn complexes that
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demonstrate oxygen atom transfer reactivity frequently invoke a Mn ꢀoxo as an intermediate;
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the molecular examples of isolated Mn ꢀoxos feature ligand fields that are exclusively or largely
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16–19
based on nitrogen donor ligands.
Mononuclear complexes with predominantly oxygen ligand
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fields are scarce, yet some manganese containing enzymes have carboxylate ligands.
Thus,
Mn in the MOFꢀ5 ligand field should provide valuable information about the effects of such a
ligand environment as well as potentially provide insight into the underpinnings of Mnꢀbased
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enzymes. Indeed, given that most known examples of isolated Mn ꢀoxos are in an allꢀnitrogen
ligand environment, we surmised that an even more reactive species could be generated in an all
oxygen ligand environment since the carboxylates comprising the SBU of MOFꢀ5 are weaker
donors. We also reasoned that the site isolated environment provided by the framework could
enhance the lifetime of the highꢀvalence intermediate by preventing dimerization or other
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deactivating reactions. With our approach, we thus targeted a system that would exhibit
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increased reactivity by providing less electronic stability to the presumed Mn ꢀoxo intermediate.
RESULTS AND DISCUSSION
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Installation of Mn within the SBU of MOFꢀ5 followed a previously reported procedure with
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slight modifications aimed at improving the crystallinity and surface area of the Mn ꢀexchanged
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MOFꢀ5 (heretofore referred to as Mn ꢀMOFꢀ5). In particular, because Mn exchanges very
rapidly into MOFꢀ5, lowering the temperature of the exchange to ꢀ35 °C and reducing the
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concentration of Mn in the exchanging solution to a molar ratio of Mn :Zn O(BDC) = 4:1
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yielded high quality material with a powder Xꢀray diffraction (PXRD) pattern that matched that
of original MOFꢀ5 (Figure S1). The BrunauerꢀEmmetꢀTeller (BET) apparent surface area of this
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material, measured by an N adsorption isotherm at 77 K, was 3100 m /g (Figure S2), a notable
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improvement over the previously reported value of 2400ꢀ2700 m /g, and inꢀline with that
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reported for original MOFꢀ5. Inductivelyꢀcoupled plasma – mass spectrometry (ICPꢀMS) of
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Mn ꢀMOFꢀ5 samples prepared by this procedure consistently gave Mn/Zn ratios of
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approximately 1/15, corresponding to one Mn ion in every four SBUs and a formula unit of
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Mn0.25Zn3.75(BDC) (Mn
ꢀMOFꢀ5). We deemed this relatively low loading of Mn desirable
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because reactive species at MOF SBUs can be a structural liability for the integrity of the entire
MOF.
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The electronic structure of the Mn ions in Mn ꢀMOFꢀ5 was probed by continuousꢀwave
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electron paramagnetic resonance (EPR) spectroscopy. Xꢀband spectra of suspensions of Mn highꢀ
MOFꢀ5 in tetrahydrofuran (THF) frozen at 77 K exhibit a single, very broad signal, indicative of
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fast spinꢀspin relaxation pathways likely stemming from the close proximity of Mn ions. To
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eliminate spinꢀspin interactions we sought to separate the Mn ions within the MOFꢀ5 lattice
even further and found that direct synthesis is more effective than postꢀsynthetic cation exchange
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in forming more magnetically dilute Mn ꢀMOFꢀ5. Thus, heating a solution of Mn(NO ) ·6H O
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with a large excess of Zn(NO ) ·6H O and terephthalic acid yielded a crystalline and porous
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Mn ꢀMOFꢀ5 sample containing only one Mn atom for every 155 Zn atoms, corresponding to a
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formula unit Mn0.026Zn3.974O(BDC) (Mn lowꢀMOFꢀ5). Xꢀband EPR spectra of this magnetically
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dilute material confirmed the essentially complete elimination of spinꢀspin interactions between
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Mn sites and exhibited an isotropic signal with the six lines of hyperfine coupling characteristic
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of highꢀspin Mn , at g = 2.021 and with a = 88 G (Figure 2).
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Mnlow-MOF-5
+ tBuSO PhIO
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Mnlow-MOF-5
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Field (Gauss)
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Figure 2. EPR of MnꢀMOFꢀ5 collected at 77 K in THF
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With evidence in hand of a Mn ion isolated in a relatively weak ligand field, Mn ꢀMOFꢀ5
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was subjected to a variety of common oxidants to probe the redox reactivity of the Mn center.
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Although Mn ꢀMOFꢀ5 shows no reactivity in the presence of O between ꢀ77 °C and 150 °C, it
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reacts readily with a variety of oxygen atom transfer (OAT) reagents. Thus, colorless crystals of
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Mn highꢀMOFꢀ5 exposed to a colorless solution of pyridine Nꢀoxide (PyNO) undergo a vivid
color change to lime green, quantified by diffuseꢀreflectance UVꢀVis (DRUVꢀVis) spectroscopy
as a new absorbance at 400 nm (Figure 3). However, the EPR signal from Mn sites upon reaction
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with PyNO, investigated using a Mn lowꢀMOFꢀ5 sample to avoid spinꢀspin relaxation, was
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identical to that of unoxidized Mn ꢀMOFꢀ5 regardless of the reaction temperature. This suggests
that the formal oxidation state of Mn remains 2+ upon reaction with PyNO, and that the observed
color change is due to a ligandꢀtoꢀmetal charge transfer band rather than a dꢀd transition as may
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be expected from a Mn or Mn . A variety of other OAT reagents of varying N—O bond
strengths, including mesityl nitrile Nꢀoxide (MesCNO, N—O bond dissociation energy (BDEN—
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O) = 53 kcal/mol) and N O (BDEN—O = 34 kcal/mol) were similarly incapable of oxidizing the
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signals characteristic of Mn .
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Wavelength (nm)
Figure 3. DRUVꢀvis of MnꢀMOFꢀ5 crystals after soaking in dichloromethane (DCM) (orange),
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and DCM solutions of PyNO (green), MesCNO (blue), and BuSO PhIO (purple).
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Although N O has a very low BDEN—O, we reasoned that its lack of redox activity towards
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Mn ꢀMOFꢀ5 is kinetic, rather than thermodynamic, and that other reagents with readily
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transferable O atoms may yet be able to oxidize Mn ꢀMOFꢀ5. In this sense, one reagent that has
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been reported to yield isolable Mn ꢀoxo complexes is iodosobenzene and its more soluble
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version tꢀbutylsulfonylꢀ2ꢀiodosylbenzene ( BuSO PhIO).
Upon exposure to a yellow solution
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of the latter, crystals of MnꢀMOFꢀ5 turn deep purple over 12 hours. This color is associated with
a new absorption at 550 nm (Figure 3) that was not observed with the other OAT reagents. Most
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low
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significantly, the EPR spectrum of Mn ꢀMOFꢀ5 crystals treated with BuSO PhIO revealed a
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significantly diminished Mn signal (Figure 2), with no overlap from other paramagnetic species.
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This suggested that the majority of Mn sites have been oxidized and transformed into an EPRꢀ
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silent species, likely Mn . Although we expected that BuSO PhIO would produce a Mn ꢀoxo,
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including DCM, as used here. Indeed, when Mn
ꢀMOFꢀ5 was treated with BuSO PhIO in
high
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deuterated chloroform (CDCl ) in the presence of cyclohexadiene, an excellent Hꢀatom donor,
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quantitative formation of benzene was observed, suggesting the intermediacy of a Mn ꢀoxo, and
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likely formation of Mn ꢀOH. Complete exclusion of Hꢀatom donors from the reaction mixture to
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ideally isolate this putative Mn ꢀoxo was unfortunately not possible because the solubility of
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BuSO PhIO is limited to DCM and CHCl . The oxidation state and the structure of the Mn site
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obtained from oxidation of Mn ꢀMOFꢀ5 with BuSO PhIO was further probed by Mn Kꢀedge Xꢀ
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that Mn ꢀMOFꢀ5 presents the same features and edge position as MnCl , our reference for Mn
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(Figure 4a). In contrast, the absorption edge for the material obtained by oxidation of Mn highꢀ
t
III
MOFꢀ5 with BuSO PhIO, purportedly Mn (OH)ꢀMOFꢀ5, shifts to higher energy and
2
III
approaches that of Mn O , our reference for Mn . Additionally, its white line decreases, also in
2
3
line with that of Mn O (Figure 4b). Edge shifts by ꢁE ≈ 3 eV accompanied by a significant
2
3
decrease and broadening of the white line are characteristic for changes in oxidation state from
II
III 30–33
III
Mn to Mn .
Although the edge position in the XANES spectrum of Mn (OH)ꢀMOFꢀ5 is
III
closer to that of Mn in Mn O than to those of MnO and MnCl , it is clearly intermediate
2
3
2
II
III
III
between Mn and Mn . This implies that Mn (OH)ꢀMOFꢀ5 contains a dominant fraction of
III
II
Mn together with a residual amount of Mn , in further agreement with the EPR studies (vide
supra).
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(
a)
(b)
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.4
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MnCl , Mn
MnO, Mn
II
2
MnCl , Mn
2
II
II
MnO, Mn
III
Mn O , Mn
III
2
3
Mn O , Mn
2
II
3
III
Mn (OH)-MOF-5
Mn -MOF-5
6
540 6550 6560 6570 6580 6590 6600 6540 6550 6560 6570 6580 6590 6600
Energy (eV) Energy (eV)
II
III
Figure 4. Mn Kꢀedge XANES spectra of Mn ꢀMOFꢀ5 (a) and Mn (OH)ꢀMOFꢀ5 (b) compared
with reference compounds.
II
Structural insight into the local environment of the Mn sites in Mn ꢀMOFꢀ5 came from
analysis of the extended Xꢀray absorption fine structure (EXAFS) data. To model this data, we
employed a DFTꢀoptimized SBU fragment, where the absorbing Mn atom is surrounded by four
O atoms in the first coordination shell, and three C and three Zn atoms in the second
coordination shell (inset Figure 5a). This structure provides a good EXAFS fit with the
experimental data (Figure 5a,b; Table S1) revealing a mean Mn—O bond distance RMn—O = 2.07
±
0.01 Å, and second shell mean distances of RMn…C = 3.00 ± 0.04 Å and RMn…Zn = 3.23 ± 0.03
…
2
2
Å. Notably, the optimized DebyeꢀWaller factor for the Mn Zn contribution, σ = 0.015 Å
Zn
(
Table S1), is too high for having a pure vibrational origin. Indeed, the corresponding Debyeꢀ
…
Waller factor obtained in fitting the Zn Zn contribution in a spectrum of pure ZnꢀMOFꢀ5,
2
34
collected at 25 °C, was previously optimized to 0.009 Å . This discrepancy is a clear indication
II
of structural local disorder in Mn ꢀMOFꢀ5, with the consequent appearance of three slightly
…
different Mn Zn distances. These cannot be resolved in the EXAFS analysis and likely account
for the amplitude decrease in the EXAFS second shell signal and the corresponding increase in
the DebyeꢀWaller parameter.
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Surprisingly, although a qualitative analysis of the Fourier Transform (FT) of the EXAFS
III
spectrum of Mn (OH)ꢀMOFꢀ5 shows a decrease in the apparent Mn—O coordination distance
II
in the first shell relative to that observed in Mn ꢀMOFꢀ5, the data also shows significantly
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
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0
1
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0
damped intensity despite the expected increase in coordination number from 4 to 5 (Figure 5c,d).
II
We attribute this counterintuitive observation to the small quantity of Mn leftover after
II
t
III
treatment of Mn ꢀMOFꢀ5 with BuSO PhIO. Because the Mn—O distances at Mn and leftover
2
II
III
II
Mn sites in Mn (OH)ꢀMOFꢀ5 differ, scattering from the Mn site is in antiphase with that from
III
the Mn site, which can account for the observed first shell signal damping in this material
II
relative to the pure Mn ꢀMOFꢀ5 sample.
Experimental
Fit
(a)
(b)
O
O
O
Mn
-3
1 Å
O
O
O
O
O
Zn
-3
Zn
0
.5 Å
Z
n
O
OO
O
O
SS O
SS O
SS C
SS C
SS Zn
SS Zn
1
2
3
1
2
3
R (Å)
R (Å)
MnO, MnII
Mn O , Mn
(c)
(d)
III
-3
2
II
3
0.4 Å
Mn -MOF-5
III
Mn (OH)-MOF-5
0
.4 Å-3
1
2
3
1
2
3
R (Å)
R (Å)
2
Figure 5. Parts (a,b): modulus (a) and imaginary part (b) of the experimental and bestꢀfit k ꢀ
II
weighted, phase uncorrected FT of the EXAFS spectra for Mn ꢀMOFꢀ5. Single scattering (SS)
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contribution involving the O, C, and Zn atomic neighbors are also reported. Parts (c,d): modulus
(c) and imaginary part (d) of the phaseꢀuncorrected FT of experimental EXAFS spectra for
III
Mn (OH)ꢀMOFꢀ5 compared with the spectra of the references and experimental spectrum of
II
0
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Mn ꢀMOFꢀ5.
t
With experimental evidence that BuSO PhIO is able to generate, at least transiently, a highꢀ
2
IV
valent, allꢀoxygen Mn ꢀoxo moiety capable of further reactivity, we sought to find substrates
where O atom transfer reactivity, rather than Hꢀatom abstraction chemistry would be observed.
II
high
t
We found that the combination of Mn
ꢀMOFꢀ5 and BuSO PhIO effects the selective
2
oxidation of cyclopentene to cyclopenteneꢀoxide catalytically in CDCl . Reaction conditions
3
were optimized to yield a maximum of seven turnovers per Mn site; this was achieved with 300
t
eq of substrate (relative to moles of Mn present), minimal solvent, and 50 eq of BuSO PhIO
2
added incrementally. Through the optimization process a linear correlation between moles of
substrate produced and moles of oxidant added became evident (Figure 6). However, the trend
plateaued at the observed maximum of 7 eq cyclopenteneꢀoxide produced. PXRD of the Mnꢀ
MOFꢀ5 after this maximum output reaction revealed the beginning of decomposition of the
framework, with a loss of crystallinity and splitting of low angle peaks (Figure S1). Reactions in
II
which MOFꢀ5 was substituted for Mn highꢀMOFꢀ5 resulted in no oxidation of substrate,
indicating that merely Lewis acid catalysis at the Zn atoms in the framework is not sufficient to
II
produce the OAT reactivity observed with Mn highꢀMOFꢀ5.
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0
t
Figure 6. Catalytic cyclopentene oxidation by MnꢀMOFꢀ5 and BuSO PhIO, conversion plotted
2
as a function of equivalents of oxidant added. The 55 eq of oxidant that was introduced for the
final data point was added in portions over the course of 7 days to prevent disproportionation of
the oxidant as a result of slow consumption.
Knowing that a likely competing reaction to epoxidation is H atom abstraction from solvent,
III
we tested whether Mn (OH)ꢀMOFꢀ5 serves as a competent preꢀcatalyst for OAT to
III
cyclopentene. Exposure of Mn (OH)ꢀMOFꢀ5 to additional oxidant and cyclopentene produced
III
more than one equivalent of cyclopenteneꢀoxide per Mn, suggesting that the Mn (OH)ꢀMOFꢀ5
indeed is a viable preꢀcatalyst for the epoxidation of cyclopentene. Reactions in which
III
Mn (OH)ꢀMOFꢀ5 was exposed to cyclopentene in the absence of additional oxidant resulted in
no OAT reactivity, eliminating it as the active catalytic species. Mn ions leached from the
framework were also ruled out as the responsible species for OAT reactivity with a hot filtration
experiment as well as experiments where Mn salts such as MnCl , MnCl with terephthalic acid,
2
2
II
MnO , and Mn O were substituted for Mn highꢀMOFꢀ5 (See Supporting Information).
2
2
3
II
high
t
The Mn
ꢀMOFꢀ5 and BuSO PhIO system serves as very selective epoxidation catalyst for
2
other cyclic alkenes, such as cyclohexene and norbornene, which are oxidized to the
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corresponding epoxides with selectivities greater than 99%. However, the relative reactivity with
each substrate correlates directly with the amount of ring strain (Table 1), and the system is not
effective in the oxidation of nonꢀcyclic olefins to epoxides or any other oxidized species, nor in
the oxidation of other hydrocarbons such as cumene and cyclohexane. Thus, ring strain is a
necessary driving force for epoxidations by this system, and hydroxylation is not a viable
reaction pathway. The lack of reactivity towards hydroxylation is perhaps best explained by the
fact that the rebound mechanism often invoked in C—H bond hydroxylation is not possible here
0
1
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0
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0
1
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6
7
8
9
0
III
due to the high stability of the Mn ꢀOH intermediate. Other metal ions may provide less stable
hydroxyl species, and thus hydroxylation reactivity, a possibility that we are currently exploring.
Additionally, we note that epoxidation reactivity requires an unobstructed approach of the double
bond to the Mn site. Indeed, we found that despite the considerable ring strain, 1ꢀ
methylcyclopentene displays no reactivity with our system. Finally, reactivity takes place
primarily within the pores of the MOF, not just on the surface of crystals, as demonstrated by
size exclusion experiments with larger cyclic olefins. Thus, cyclododecene, despite a relatively
35
high ring strain value, undergoes less than one turnover when subjected to reaction conditions.
We surmise that the low reactivity of this molecule is due to its size (7.2 Å at its widest point, not
including solvation sphere), which does not allow it to easily penetrate the approximately 10 Å
pores of MOFꢀ5, an observation that is consistent with the use of this substrate in systems with
3
6
similar pore sizes.
Table 1. Correlation of substrate reactivity on ring strain energy
a
37
Substrate
Norbornene
Cyclopentene
# of Turnovers per Mn
Ring Strain energy
3
7
8.80
5.52
21.6 kcal/mol
3
7
4.8 kcal/mol
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1
ꢀmethyl cyclopentene
Cyclohexene
0
3.9 kcal/mol
0.3 kcal/mol
7.0 kcal/mol
1.55
Cyclooctene
3.60
0.60
35
Cyclododecene
10 kcal/mol
1
1
1
1
1
1
1
1
1
1
2
2
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2
2
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2
2
2
2
3
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0
1
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8
9
0
II
a. Reaction conditions: 10 mg Mn highꢀMOFꢀ5, 600 eq substrate, 8 eq oxidant, 0.7 mL CDCl3,
8 h at RT.
1
II
Fundamentally, the Mn ꢀMOFꢀ5 system allows the unique opportunity to study the reactivity
III
III
of a rare terminal Mn ꢀOH species. Most molecular examples of Mn ꢀOH species are poor
candidates for reactivity studies due to the amount of steric bulk that is necessary to keep such a
2
9,38,39
III
moiety from dimerizing or forming ꢂꢀoxo/hydroxo bridges.
species do not require steric protection, they tend to have limited or nonꢀcatalytic reactivity.
As is the case with some of the existing examples, it is reasonable to assume that the formation
In turn, when known Mn ꢀOH
4
0,41
III
IV
29
III/V
of Mn (OH)ꢀMOFꢀ5 proceeds through a Mn ꢀoxo intermediate. Although the Mn
couple
4
2,43
II
is better known for selective epoxidation reactivity,
it is not unprecedented for Mn to
generate epoxides in the presence of an oxidant, though not as selectively as we have shown in
4
4
IV
II
this work. Importantly, Mn ꢀoxo species generated from Mn precursors can also produce
various distributions of alcohols and downstream epoxide oxidation products by introducing
small changes in experimental conditions (such as ligand scaffold or protonation of the oxo with
45
II
HOTf). In our system, the eventual decomposition of Mn highꢀMOFꢀ5 over multiple
IV
consecutive turnovers further suggests the occurrence of a Mn ꢀoxo intermediate. The current
reactivity nevertheless suggests that with small changes, the product distribution may be changed
in a fashion mimicking that seen in molecular systems.
CONCLUSION
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II
The foregoing results demonstrate that Mn ꢀMOFꢀ5 is competent for oxygen atom transfer
reactivity in a catalytic fashion. Although the relative instability of this system under sustained
catalytic conditions likely prevents its use in industrial applications, the demonstrated reactivity
and proposed intermediate highlight a unique opportunity with MOFs to study species of
0
1
2
3
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5
6
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fundamental interest. Specifically, the observed reactivity and the isolation of a terminal Mn ꢀ
IV
OH moiety are consistent with the transient formation of a Mn ꢀoxo species. This putative highꢀ
valent Mn species acts as a highly selective catalyst for the epoxidation of cyclic olefins, a
III
reactivity that is reproduced with the Mn ꢀOH species, itself a rare occurrence in a weak ligand
field environment such as that afforded by the nodes of MOFꢀ5.
ASSOCIATED CONTENT
The following files are available free of charge.
Supporting Information.
Details of experimental procedures and results, PXRD, and nitrogen isotherm data (PDF).
AUTHOR INFORMATION
Corresponding Author
mdinca@mit.edu
Author Contributions
The manuscript was written through contributions of all authors. All authors have given
approval to the final version of the manuscript.
Funding Sources
NSF GRFP, MITei / ExxonMobil, and Russian Federation Government.
ACKNOWLEDGMENT
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This research was supported by ExxonMobil Corporate Strategic Research through the MIT
Energy Initiative. A.W.S. gratefully acknowledges the National Science Foundation Graduate
Research Fellowship program for financial support under Grant No.1122374. Fundamental
studies of cation exchange are supported through an NSF Career grant to M.D. (DMRꢀ1452612).
We thank Dr. G. Agostini for assistance with the XAS data collection at ESRF BM23 and Dr. H.
Müller for his support in the ESRF chemistry laboratory. Kirill A Lomachenko and Andrea
Melloni are acknowledged for their support during the XAS data collection and for fruitful
discussion on the XAS data analysis. C.L. and L.B. acknowledge the Megaꢀgrant of the Russian
Federation Government (14.Y26.31.0001).
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REFERENCES
(1)
Chughtai, A. H.; Ahmad, N.; Younus, H. A.; Laypkov, A.; Verpoort, F. Chem. Soc. Rev.
2015, 44, 6804–6849.
(2)
Farrusseng, D.; Aguado, S.; Pinel, C. Angew. Chem. Int. Ed. 2009, 48, 7502–7513.
Gascon, J.; Corma, A.; Kapteijn, F.; Llabrés i Xamena, F. X. ACS Catal. 2014, 4, 361–
(3)
3
78.
(4)
Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. Science. 2013, 341,
1230444/1ꢀ1230444/12.
(5)
Brozek, C. K.; Dincă, M. Chem. Soc. Rev. 2014, 43, 5456–5467.
(6)
Brozek, C. K.; Miller, J. T.; Stoian, S. A.; Dincă, M. J. Am. Chem. Soc. 2015, 137, 7495–
7
501.
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6
7
8
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
(
(
7)
8)
9)
Park, H. D.; Dincă, M.; RománꢀLeshkov, Y. ACS Cent. Sci. 2017, 3, 444–448.
Metzger, E. D.; Brozek, C. K.; Comito, R. J.; Dincă, M. ACS Cent. Sci. 2016, 2, 148–153.
Centi, G.; Cavani, F.; Trifirò, F. Trends and Outlook in Selective Oxidation: An
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
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9
0
1
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3
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5
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1
2
3
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0
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2
3
4
5
6
7
8
9
0
st
Introduction. Selective Oxidation by Heterogeneous Catalysis, 1 ed.; Springer US, New
York, 2001 p 1ꢀ24.
(
(
(
10) Labinger, J. A.; Bercaw, J. E. Nature 2002, 417, 507–514.
11) Ravi, M.; Ranocchiari, M.; van Bokhoven, J. A. Angew. Chem. Int. Ed. 2017, 56, 2ꢀ22.
12) Centi, G.; Cavani, F.; Trifirò, F. New Concepts and New Strategies in Selective
st
Oxidation. Selective Oxidation by Heterogeneous Catalysis 1 ed.; Springer US, New
York, 2001; pp 325–362.
(13) Whittall, J. In Regioꢀ and Stereoꢀ Controlled Oxidations and Reductions; Stanley M.
Roberts, Whittall, J., Eds.; John Wiley & Sons, Ltd, 2007; Vol. 5, pp 1–33.
(
14) Werpy, T.; Petersen, G. Top Value Added Chemicals from Biomass Volume I — Results of
Screening for Potential Candidates from Sugars and Synthesis Gas; DOE/GOꢀ102004ꢀ
1
992; US Department of Energy: United States, 2004; p 10.
(15) Kuwahara, Y.; Yoshimura, Y.; Yamashita, H. Dalt. Trans. 2017, 46, 8415–8421.
(
16) Barman, P.; Vardhaman, A. K.; Martin, B.; Wörner, S. J.; Sastri, C. V.; Comba, P. Angew.
Chem. Int. Ed. 2015, 54, 2095–2099.
(17) Parsell, T. H.; Behan, R. K.; Green, M. T.; Hendrich, M. P.; Borovik, A. S. J. Am. Chem.
Soc. 2006, 128, 8728–8729.
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(
(
(
18) Wu, X.; Seo, M. S.; Davis, K. M.; Lee, Y.ꢀM.; Chen, J.; Cho, K.ꢀB.; Pushkar, Y. N.; Nam,
W. J. Am. Chem. Soc. 2011, 133, 20088–20091.
19) Yoon, J.; Seo, M. S.; Kim, Y.; Kim, S. J.; Yoon, S.; Jang, H. G.; Nam, W. Bull. Korean
Chem. Soc. 2009, 30, 679–682.
1
1
1
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0
20) Whittaker, M. M.; Barynin, V. V.; Antonyuk, S. V.; Whittaker, J. W. Biochemistry 1999,
3
8, 9126–9136.
(21) Ferreira, K. N. Science. 2004, 303, 1831–1838.
(22) Brozek, C. K.; Dincă, M. J. Am. Chem. Soc. 2013, 135, 12886–12891.
(23) Kaye, S. S.; Dailly, A.; Yaghi, O. M.; Long, J. R. J. Am. Chem. Soc. 2007, 129, 14176–
4177.
1
(24) Matzapetakis, M.; Karligiano, N.; Bino, A.; Dakanali, M.; Raptopoulou, C. P.; Tangoulis,
V.; Terzis, A.; Giapintzakis, J.; Salifoglou, A. Inorg. Chem. 2000, 39, 4044–4051.
(25) Reed, G. H.; Cohn, M. J. Biol. Chem. 1973, 248, 6436–6442.
(26) Holm, R. H.; Donahue, J. P. Polyhedron 1993, 12, 571–589.
(27) Severin, K. Chem. Soc. Rev. 2015, 44, 6375–6386.
(28) Yoon, H.; Morimoto, Y.; Lee, Y.ꢀM.; Nam, W.; Fukuzumi, S. Chem. Commun. 2012, 48,
1
1187–11189.
(29) Shirin, Z.; Young, V. G.; Borovik, A. S. Chem. Commun. 1997, 36, 1967–1968.
(30) Fernández, G.; Corbella, M.; Alfonso, M.; StoeckliꢀEvans, H.; Castro, I. Inorg. Chem.
ACS Paragon Plus Environment
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Page 20 of 22
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5
5
5
5
5
5
5
6
2
004, 43, 6684–6698.
(
(
(
(
31) Stueben, B. L.; Cantrelle, B.; Sneddon, J.; Beck, J. N. Microchem. J. 2004, 76, 113–120.
32) Manceau, A.; Marcus, M. A.; Grangeon, S. Am. Mineral. 2012, 97, 816–827.
33) Xu, L.; Liu, W.; Li, X.; Rashid, S.; Shen, C.; Wen, Y. RSC Adv. 2015, 5, 12248–12256.
0
1
2
3
4
5
6
7
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9
0
1
2
3
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0
34) Hafizovic, J.; Bjørgen, M.; Olsbye, U.; Dietzel, P. D. C.; Bordiga, S.; Prestipino, C.;
Lamberti, C.; Lillerud, K. P. J. Am. Chem. Soc. 2007, 129, 3612–3620.
(
35) Lerum, M. F. Z.; Chen, W. Langmuir 2011, 27, 5403–5409.
(
36) Moliner, M.; Serna, P.; Cantin, A.; Sastre, G.; DiazꢀCabanas, M. J.; Corma, A. J. Phys.
Chem. C 2008, 112, 19547–19554.
(37) Khoury, P. R.; Goddard, J. D.; Tam, W. Tetrahedron 2004, 60, 8103–8112.
(38) Shook, R. L.; Peterson, S. M.; Greaves, J.; Moore, C.; Rheingold, A. L.; Borovik, A. S. J.
Am. Chem. Soc. 2011, 133, 5810–5817.
(
39) Shirin, Z.; Hammes, B. S.; Young, V. G.; Borovik, A. S. J. Am. Chem. Soc. 2000, 122,
1
836–1837.
(40) Goldsmith, C. R.; Cole, A. P.; Stack, T. D. P. J. Am. Chem. Soc. 2005, 127, 9904.
(41) Eichhorn, D. M.; Armstrong, W. H. J. Chem. Soc., Chem. Commun. 1992, 20, 85–87.
(
42) Guo, M.; Dong, H.; Li, J.; Cheng, B.; Huang, Y.; Feng, Y.; Lei, A. Nat. Commun. 2012, 3,
–9.
1
(
43) Collman, J. P.; Zeng, L.; Wang, H. J. H.; Lei, A.; Brauman, J. I. European J. Org. Chem.
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Page 21 of 22
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006, 12, 2707–2714.
(
44) Lymperopoulou, S.; Papastergiou, M.; Louloudi, M.; Raptopoulou, C. P.; Psycharis, V.;
Milios, C. J.; Plakatouras, J. C. Eur. J. Inorg. Chem. 2014, 2014, 3638–3644.
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0
(45) Kim, S.; Cho, K. Bin; Lee, Y. M.; Chen, J.; Fukuzumi, S.; Nam, W. J. Am. Chem. Soc.
016, 138, 10654–10663.
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For Table of Contents Only
II
t
IV
Synopsis: Mn ꢀMOFꢀ5 exposed to a solution of BuSO PhIO produces a putative Mn ꢀoxo
2
III
intermediate, which upon further reaction with adventitious hydrogen is trapped as a Mn ꢀOH
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species. The intermediacy of the highꢀspin Mn ꢀoxo species is likely responsible for catalytic
II
t
activity of the Mn ꢀMOFꢀ5 preꢀcatalyst, which in the presence BuSO PhIO catalyzes oxygen
2
atom transfer reactivity to form epoxides from cyclic alkenes with >99% selectivity.
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