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COMMUNICATION
Journal Name
III
2–, as
ponding Fe -OH
2
complex through ET oxidation by S
2
O
8
3
4
5
6
Rev., 2005, 105, 2253-2278.
J. C. Price, E. W. Barr, B. Tirupati, J. M. Bollinger Jr. and C. Krebs,
Biochemistry, 2003, 42, 7497-7508.
DOI: 10.1039/D0CC03289A
confirmed by ESR spectroscopy after the reaction of 1·(NO
)
3 2
III
with Na
is further oxidized by SO
which is known to exhibit extremely strong oxidizing power,
S
2 2
O
8
(step I in Fig. 5; see Fig. S12). The Fe -OH
2
complex
•–
IV
4
to form an Fe =O active species,
S. Ye and F. Neese, Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 1228-
26
1
233.
III
IV
2
enough to oxidize the Fe -OH complex to the Fe =O complex;
E(Fe /Fe ) = +1.92 V vs. SCE in CH
clarify the characteristics of the reactive species formed by 2e -
oxidation of 1, DFT calculations were performed on a Fe-O
complex including two H O molecules interacted with the
2
oxygen ligand at the B3LYP/6-311+G** level of theory (Fig. S13).
The results suggest that the triplet Fe =O state is the most
stable (Table S4). The Fe=O distance in the optimized structure is
.668 Å and the bond order is 1.83. After the pre-equilibrium
process to form an adduct between the active species and EtPhS
step III, see Fig. 2), EtPhS is oxidized through the C-H bond
cleavage as the RDS to afford the 2e -oxidized product (step IV,
KIE shown in Fig. 3). In the final step V, the oxidized product
coordinated to Fe centre is substituted by a water molecule to
complete the catalytic cycle (see Fig. S9).
C. V. Sastri, J. Lee, K. Oh, Y. J. Lee, J. Lee, T. A. Jackson, K. Ray, H.
Hirao, W. Shin, J. A. Halfen, J. Kim, L. Que Jr., S. Shaik and W.
Nam, Proc. Natl. Acad. Sci. U. S. A., 2007, 104, 19181-19186.
J.-U. Rohde, J.-H. In, M. H. Lim, W. W. Brennessel, M. R. Bukowski,
A. Stubna, E. Münk, W. Nam and L. Que Jr., Science, 2003, 299,
1037-1039.
III
IV
Cl
2 2
(see above, step II). To
–
7
IV
8
9
N. Y. Oh, Y. Suh, M. J. Park, M. S. Seo, J. Kim and W. Nam, Angew.
Chem., Int. Ed., 2005, 44, 4235-4239.
J. Kaizer, E. J. Klinker, N. Y. Oh, J.-U. Rohde, W. J. Song, A. Stubna,
J. Kim, E. Münck, W. Nam and L. Que Jr., J. Am. Chem. Soc. 2004,
1
126, 472-477.
(
1
0 J. M. Mayer, Acc. Chem. Res., 1998, 31, 441-450.
–
11 D. Wang, M. Zhang, P. Buhlmann and L. Que Jr., J. Am. Chem. Soc.,
2010, 132, 7638-7644.
1
2 J. Kaizer, E. J. Klinker, N. Y. Oh, J.-U Rohde, W. J. Song, A. Stubna, J.
Kim, E. Münk, W. Nam and L. Que Jr., J. Am. Chem. Soc., 2004,
126, 472-473.
In conclusion, we have demonstrated catalytic oxidation
3 2
reactions by an NHC-ligated Fe-complex, 1·(NO )
as a catalyst to 13 T. Chantarojsiri, Y. Sun, J. R. Long and C. J. Chang, Inorg. Chem.
–
2015, 54, 5879-5887.
afford 2e -oxidized products with high selectivity by suppression
of overoxidation in water. Although details of the reactive
species in the reactions have yet to be clarified, the reactive
species derived from 1 should have a strong oxidative activity
due to the strong trans-influence from the NHC moiety.
1
1
4 J. M. Smith and J. R. Long, Inorg. Chem., 2010, 49, 11223-11230.
5 Y. Shimoyama, T. Ishizuka, H. Kotani, Y. Shiota, K. Yoshizawa, K.
Mieda, T. Ogura, T. Okajima, S. Nozawa, T. Kojima, Angew. Chem.,
Int. Ed., 2016, 55, 14041-14045.
1
6 Y. Shimoyama, T. Ishizuka, H. Kotani, T. Kojima, ACS Catal., 2019,
9
, 671-678.
1
1
7 Y. Shimoyama and T. Kojima, Inorg. Chem., 2019, 58, 9517-9542.
8 In the asymmetric unit, two independent moieties of 1 were
inluded. Thus, the bond length is the mean vaue of the two
independent molecules of 1.
1
9 Although BDE of the benzylic C-H bonds in EtPhS is higher than
that in CumS, the TONs divided by the number (n) of the
equivalent C-H bonds in the substrates were almost the same: 21
for EtPhS (n = 2) and 26 for CumS (n = 1).
20 M. Ghosh, K. K. Singh, C. Panda, A. Weits, M. P. Hendrich, T. J.
Collins, B. B. Dhar and S. S. Gupta, J. Am. Chem. Soc., 2014, 136,
9
524-9527.
1 To confirm that the oxygen atoms of Na
2 2 8
with solvent water molecules, IR spectra of Na S O
2
S O
2 2 8
do not exchange
were
O and the
Fig. 5
A proposed mechanism of the oxidation of EtPhS by 1 and S
2
O
8
2–.
18
measured before and after the treatment with H
2
spectra were almost the same without any shifts of the S=O and
O-O stretching bands (Fig. S10).
2 I. Garcia-Bosch, A. Company, C. W. Cady, S. Styring, W. R. Browne,
This work has been supported by JST CREST (Grant
JPMJCR16P1) and Grants-in-Aid (15H00915, 17H03027, and
2
18K19089) from the Japan Society of Promotion of Science
X. Ribas and M. Costas, Angew. Chem., Int. Ed., 2011, 50, 5648-
(JSPS).
5
653.
3 E. A. Mader, E. R. Davidson and J. M. Mayer, J. Am. Chem. Soc.,
007, 129, 5153-5166.
2
2
2
2
2
Conflicts of interest
There are no conflicts to declare.
4 Y.-R. Luo, Handbook of bond dissociation energies in organic
compounds, 2003.
5 M. Finn, R. Friedline, N. K. Suleman, C. J. Wohl and J. M. Tanko, J.
Am. Chem. Soc., 2004, 126, 7578-7584.
•–
6 A high reduction potential of SO
4
has been reported to be +2.19
Notes and references
V vs. SCE in water. R. E. Huie, C. L. Clifton and P. Neta, Int. J.
Radiat. Appl.Instrum. C, 1991, 38, 477-481.
1
M. Costas, M. P. Mehn, M. P. Jensen and L. Que Jr., Chem. Rev.,
004, 104, 939-986.
M. Ekroos and T. Sjogren, Proc. Natl. Acad. Sci. U. S. A., 2006, 103,
3682-13687.
2
2
1
4
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